Are cattle capable of producing litters of calves? - McMillan WH; Peterson J; Thompson J; Pugh PA (Proceedings of the New Zealand Society of Animal Production, 1999)
Early embryo survival was examined in recipient heifers following the transfer of either 5 or 15 (Expt 1, N=19), or either 2 or 10 (Expt 2, N=46) in vitro produced embryos transferred into the same uterine horn. In Expt 1, the mean ± s.e. number of conceptuses per pregnant recipient was 2.5 ± 0.6 and 10.8 ± 0.8 (P<0.001) in recipients receiving either 5 or 15 embryos. Overall, 63 ± 4% of embryos survived (mean ± s.d.), with no difference among recipients receiving 5 embryos and examined on Day 15, or receiving 15 embryos and slaughtered on either Day 15 or Day 22 (56 ± 10%, 77 ± 5% and 68 ± 5%, respectively, X² = 3.67, NS). Survival was inexplicably lower on Day 22 in recipients receiving 5 embryos (24 ± 9% vs. 69 ± 4%, X² = 19.15, P<0.001). Pregnancy rate was similar in heifers receiving either 5 or 15 embryos (9/9 vs. 8/10, X² = 2.01, NS), and the mean ± se number of conceptuses per pregnant recipient was 2.5 ± 0.6 vs. 10.8 ± 0.8, (P<0.001). In Expt 2, embryo survival was 80 ± 5% and 73 ± 2% (NS), and the mean ± s.e. number of conceptuses per pregnant recipient 1.6 ± 0.2 and 7.3 ± 0.3 (P<0.001) in recipients receiving either 2 or 10 embryos. These preliminary results demonstrate that recipient cattle are apparently capable of supporting large numbers of viable conceptuses (5-15) up until at least the fourth week of pregnancy. Whether these can be maintained to term is yet to be demonstrated, although published evidence suggests that the biological limit may be 5 calves per cow at term.

Attempted Transmission of Brucella ovis between stags and from stags to rams - West DM; Stafford KJ; Sargison ND; Fenwick SG; Reichel MP (Proceedings of the New Zealand Society of Animal Production, 1999)
In August 1997 three 9-month-old Red x Wapiti stags were inoculated intravenously with Brucella ovis. Between October 1997 and June 1998 these three stags were grazed with 8 control stags of a similar age and 10 one-year-old Perendale rams, which had been confirmed free from B. ovis infection before mixing. At monthly intervals the 11 stags and 10 rams were blood sampled for B. ovis serology and when infection was suspected, this was confirmed by bacterial culture of a semen sample. Two of the three artificially infected stags became persistently infected with B. ovis and shed the organism in their semen. They remained positive to the B. ovis complement fixation (CF) serological test throughout the trial. The CF titre fell below the positive cut-off level 4 months after inoculation in the other artificially infected stag which did not develop persistent B. ovis infection. During April and May 1998, 7 months after mixing with the artificially infected animals, B. ovis infection was identified in 4 of the 8 control stags. There was no evidence of B. ovis transmission to the control rams. The trial demonstrated the rapid transmission of B. ovis infection between young stags during the rut. This would suggest that sexual activity is important for B. ovis to spread, although the exact means of transmission could not be determined. Rams grazed in conjunction with B. ovis - infected stags have a lower risk of becoming infected.

Brief Communication: The combination of the n-alkanes and the 13C methods as a new tool for estimating individual DM intakes of pasture and maize silage by grazing dairy cows - Garcia SC; Holmes CW; Hodgson J; MacDonald A (Proceedings of the New Zealand Society of Animal Production, 1999)
It is very difficult to measure DM intakes by indi-vidual grazing animals, particularly if these animals are being supplemented as a group, and the individual intakes of both pasture (P) and supplement are of interest. When the supplement is maize silage (MS), the difference in the proportions of the stable isotope 13 C between temperate P and MS could be combined with the n-alkane method for this purpose. The experiment described here was conducted to test this method and also to measure the variation be-tween individual cows in the amount of MS eaten daily.

Can Beta-hydroxybutyrate levels predict postpartum anoestrous interval of dairy cows? - Verkerk GA; Guiney JC (Proceedings of the New Zealand Society of Animal Production, 1999)
Concentrations of b-hydroxybutyrate in plasma (pBOH) and milk (mBOH) were measured post-partum (pp). Mean pBOH levels were highest in Weeks 3&4 pp (1.1 ± 0.1 mmol/L). Cows were grouped for length of post-partum anoestrous interval (PPAI) for the statistical analyses. Of those cows which required hormonal treatment because they were anoestrous at the planned start of mating, 77% had pBOH >1 mmol/L during Weeks 1&2 pp, compared to 52% of other cows (P < 0.1). Levels of pBOH alone could not predict the length of the PPAI (r2 = 2%). Logistic regression analyses confirmed age, calving live-weight and calving condition score as risk factors for prolonged PPAI. When these factors were considered with pBOH at Weeks 5&6 pp, a predictive relationship was found (P < 0.05). Levels of mBOH and pBOH were related (r2 = 0.68; P < 0.001). These results support negative energy balance in early lactation as a risk factor for prolonged PPAI, along with age and live-weight and body condition score at calving.

CF2000 - a new way of looking at the same information - McCorkindale AB (Proceedings of the New Zealand Society of Animal Production, 1999)
The CF2000 farm monitoring programme enables farmers to monitor factors relevant to their property and management, as well as enabling comparisons to be made with other members of the group through benchmarking. Data recording is divided into a compulsory core section and an optional section. Data is processed by a bureau, and the reports which include a variety of graphs showing an individuals performance relative to the group, are returned to participating farmers along with comments from the farm-ers consultant. Members-only field days are held three times per year for educational and motivational purposes.

Changes in unscourable discolouration of Romney wool samples during storage for one month - Bray AR; O'Connell D; Smith MC (Proceedings of the New Zealand Society of Animal Production, 1999)
Samples of four Romney fleeces were dried to 8% moisture immediately after harvesting, then water was added to achieve moisture contents of 8, 19, 30, 41 or 52% of the clean, dry wool weight. Additional samples were left untreated (11 % moisture) or scoured (16% moisture). CIE X, Y, Z and Y-Z measures of scoured wool colour were recorded after 0, 5, 12, 21 or 33 days storage at 3 or 20° C. There was no change in colour values of untreated and scoured samples during storage at 3 or 20° C. X, Y and Z values decreased linearly when moisture content increased (P<0.05), the effect being most marked at 20°C. A trend for Y-Z values to increase with moisture content was not significant. The findings indicate that if damp greasy wool is to be stored for a month or more before colour is measured, it should be dried at 30°C or less before storage, stored at cool temperatures, or scoured and dried before storage.

Compensatory growth in lambs undernourished from birth - Bass J; Kirton A; Oldham J (Proceedings of the New Zealand Society of Animal Production, 1999)
There is evidence to suggest that lambs on restricted nutrition from birth fail to show compensatory growth. In this indoor trial, lambs were allocated to one of three treatments and fed on lamb milk formula, then sheep pellets. Lambs were started on high (H) or low (L) rates of intake from 3 days of age. Groups of L lambs were subsequently placed on H intakes (low-high; L-H) at 2, 4 and 8 months of age and killed at 4, 8 and 15 months of age respectively. At 15 months H lambs weighed 86.2 kg and L lambs 28.6 kg. The growth rates of L-H ranged between 224 and 242 g/d during compensatory growth. The H lambs averaged 186 and L lambs 50 g/d during the experiment. At slaughter, there was no difference between H and L-H lambs for hot carcass weight when adjusted for final live weight, and little change in the weight and length of M. semitendinosus. Hind limb dissection also demonstrated no effect of nutritional treatment on proportions of muscle, bone and fat in H and L-H lambs. These results suggest that lambs on restricted nutrition from birth retain their potential to grow if provided with improved nutrition.

Contract References - Anonymous (Proceedings of the New Zealand Society of Animal Production, 1999)
CONTRCT REFERENCES Agricultural Research Council. 1980 The nutrient requirements of rumi-nant livestock. Commonwealth Agricultural Bureaux, Farnham Royal, England. Anon, 1999. The New Zealand sheep and beef farm survey 1996-97. Meat and Wool Economic Service of New Zealand. 71pp. Chamberlain, D.G.; Martin, P.A.; Robertson, S. 1996. Optimising com-pound feed use in dairy cows with high intakes of silage. Recent Developments in Ruminant Nutrition 3: 245-263. Dalton, D.C.; Knight, T.W.; Johnson, D.L. 1980. Lamb survival in sheep breeds on New Zealand hill country. New Zealand Journal of Agricultural Research 23: 167-173. Davis, G.H.; Kelly, R.W.; Hanrahan, J.P.; Rohloff, R.M. 1983. Distribu-tion of litter size within flocks of different levels of fecundity Proceedings of the New Zealand Society of Animal Production, 43: 25-28.

Dag formation - Cottle D; Reid TC (Proceedings of the New Zealand Society of Animal Production, 1999)
Dags are a major cost in sheep farming. This paper reports on differences in wool yield and mineral content of faeces associated with dag formation. Of 600 hoggets on a farm in Inland Canterbury, only three had dag scores greater than 0.5 in mid-March (mean dag score 0.030). After 10 weeks (mean dag score 0.4), 80% of the animals recorded a dag score 0.5 or less and 40 animals (6.7%) had dag scores of 2 or greater. In two other trials, wool samples showed no differences in wool grease, suint content or yield associated with differences in dagginess of the animals. Fresh faeces were collected from ewes from the Resistant (R) and Susceptible (S) FEC selection lines at Wallaceville which differ in dag formation. These lines did not differ in faecal dry matter, phosphorus, calcium, magnesium, sodium or potassium content. Lambs from these lines differed significantly in faecal potassium (mean = 13.8 mg/kg, R-S = 2.98 mg/kg (P<0.001)) and magnesium (mean = 5.7 g/kg, R-S = -0.82 g/kg (P<0.05)) contents. Faeces from lambs grazing low or high endophyte pasture also differed in potassium (12.8 vs. 15.3 g/kg, SED 1.18) and magnesium (7.6 vs. 6.0 g/kg, SED 0.67) content. These results point to differences in faeces associated with differing dag forming tendencies and may assist in explaining some of the mechanisms involved in dag formation.

Development of fibre and follicle characteristics related to wool bulk in hoggets of genotypes used to develop GrowBulk sheep - Sumner RMW (Proceedings of the New Zealand Society of Animal Production, 1999)
Wool fibre and follicle development was monitored in 40 hoggets born in 1996 comprising sex-balanced groups of Romney (R), Dorset x Romney (DR), Texel x Romney (TR) and DR x TR and TR x DR (DTR) sheep between 3 and 12 months of age. There was a significant curvilinear pattern of development for fibre curvature and follicle curvature for the DR, TR and DTR groups whereas values for the R group did not change significantly with time. Fibre diameter was not significantly different between the groups. A combination of fibre curvature and fibre diameter explained approximately 70% of the variation in core bulk within all genotypes at hogget shearing for samples taken at points in time during growth of the fleece. The combination of fibre curvature and fibre diameter is a useful predictor of adult wool bulk to assist breeders of GrowBulk sheep.

Discriminating among animals for improved rewards from traditional meat cuts - Jopson NB; Clarke JN (Proceedings of the New Zealand Society of Animal Production, 1999)
The influence of biological variation on animal numbers meeting specifications based on alternative indicators of carcass merit to GR and carcass weight (CW), and the value of live animal indicators in meeting particular goals were investigated. Percentages of carcasses achieving a two-trait (GR: 5.5 to 9.5mm; and CW: 15.5 to 17.5kg) and a three-trait (GR, CW and various leg lengths: T) specification were analytically derived over multivariate normal distributions. Two `populations` of sheep were considered; one with a mean CW, GR and T of 14.6kg, 6.8mm and 184mm, respectively, and the second with mean values of 15.5kg, 6.8mm and 186mm. Adding conformational traits reduced the proportion achieving the specification, with the reduction being greater if the correlations between traits were antagonistic. Analysis of potential carcass merit indicators from experimental dissection data indicated that 8% of the variation in leg weight was associated with sire breed, sire, sex and birth rank effects, while 32% was associated with animal variations in six linear indicators (high GR, low subcutaneous leg fat depth, high carcass length, T, high proximal leg circumference, and low total length of the leg joint). Together these two classes of indicators accounted for 36% of the total variation among lambs.

A Dynamical Model of Body Composition in Sheep - Soboleva TK; Oddy VH; Pleasants AB; Oltjen JW; Ball AJ; McCall DG (Proceedings of the New Zealand Society of Animal Production, 1999)
A dynamical model describing the evolution of muscle, viscera and fat in response to different levels of energy intake over time in sheep is presented. The model shows responses consistent with observations of compensatory growth in sheep and cattle over a range of energy intake levels. Model parameters are derived from data measured by Ferrell et al., (1986) to investigate compensatory growth in lambs. The model is shown to generally reproduce the behaviour of the muscle, viscera and fat components of the lambs in this trial. The utility of the model for designing optimal nutritional management strategies for raising animals for slaughter is discussed, as well as the potential of the model to advance the understanding of animal nutrition by investigating different functional forms for relationships such as maintenance requirements.

Effect of long acting injectable vitamin B12 on the vitamin B12 status of the suckling lamb - Grace ND (Proceedings of the New Zealand Society of Animal Production, 1999)
Treatment of lambs with a long acting microencapsulated injection of 3mg and 6mg Vitamin B12 at 3 to 4 weeks of age, at docking, will increase and maintain their Vitamin B12 status for at least 120 days. This new product has the advantage over intraruminal Co bullets which can only be administered to 10 to 12 week old lambs with a functional reticulorumen while the injectable water soluble Vitamin B12 is only effective for about 4 weeks and a Co drench is effective for about 10 days.

Effect of Lotus corniculatus and condensed tannins on milk yield and composition of dairy cows - Woodward SL; Clark DA; Laboyrie PJ; Jansen EBL (Proceedings of the New Zealand Society of Animal Production, 1999)
Experiments at DRC have demonstrated birdsfoot trefoil (Lotus corniculatus) increases milk yield and milk protein concentra-tion of grazing dairy cows. An experiment was conducted in March 1998 to determine what proportion of the increased milk yield and milk protein% was due to the condensed tannins (CT) in Lotus, and what proportion was due to factors typically associated with legumes (increased herbage intake and improved forage quality). Twenty Friesian cows were housed and fed twice daily on either perennial ryegrass or Lotus for 10 days. Five cows on each diet were also drenched with 1.2 l of 50% polyethylene glycol (PEG) three times per day. PEG blocks the action of CT, preventing them binding to plant proteins. Milk yields (l/cow/d) were higher on Lotus (16.5) than on Lotus+PEG (13.8), ryegrass (10.2) or ryegrass+PEG (9.9) indicating that CT contributed to 42% of the increased milk yield that resulted from feeding Lotus rather than ryegrass. CT had no effect on intake, since intakes (kgDM/cow/d) of cows fed Lotus (16.8) and Lotus+PEG (16.7) were similar and higher than for cows fed either ryegrass (14.7) or ryegrass+PEG (13.7). CT, however, accounted for all of the increase in herbage conversion efficiency as indicated by the higher efficiencies (ml FCM/MJ ME) of cows fed Lotus (147) compared with those fed Lotus+PEG (126), ryegrass (123) or ryegrass+PEG (127). CT accounted for 57% of the increase in milk protein% as cows fed Lotus (3.61) had higher protein% than those fed Lotus+PEG (3.44), ryegrass (3.31) or ryegrass+PEG (3.30). Herbage or CT had no effect, however, on the casein or whey protein concentrations. CT had no effect on either milk fat or lactose concentration but cows fed Lotus had lower concentrations than cows fed ryegrass (P<0.05). Overall the trial showed legumes containing CT have potential as a forage for dairy cows.

Effect of recipient breeds on birth and weaning weight, and wool follicle characteristics of Merino lambs born by embryo transfer - Wuliji T; Dodds KG; Andrews RN; Aspinall J; Harrison T (Proceedings of the New Zealand Society of Animal Production, 1999)
One hundred and eighty three embryos were collected from 29 donor Merino ewes and transferred as either a single or twins to Merino (MR), Coopworth (CR) and Romney (RR) recipient dams. A total of 107 lambs were weaned from these implants. A control group (MN) of 24 naturally conceived single and twin lambs were included for comparison. Follicle fibre diameters at birth were 16.7, 17.2, 17.7 and 17.6 mm (SED 0.4) for MN, MR, CR and RR respectively; while the fibre diameter of wool samples at birth for all dam groups was 16.5 mm (SED 0.3). Follicle fibre diameters at weaning were 16.5mm, 15.9, 16.3 and 16.1 (SED 0.6) for MN, MR, CR and RR respectively while the corresponding wool FDs at weaning were 16.3 mm, 16.1, 16.0, and 16.0 (SED 0.4). Weaning weight was similar in CR and RR, while CR weaned significantly heavier lambs than Merinos (recipients or naturally bred). The results suggest that crossbred dams improve weaning weights of Merino lambs born to embryo transfer but do not affect their wool follicle character-istics.

Effect of selection for fleece weight on liveweight, reproductive performance and wool characteristics in mixed age Romney ewes - Wuliji T; Dodds KG; Andrews RN; Turner PR; Wheeler R (Proceedings of the New Zealand Society of Animal Production, 1999)
This paper presents the analysis of 3525 annual production records of mixed age Romney ewes in a fleece weight selected (HF) or control (RC) flock over 11 years. HF ewes were significantly (P<0.001) heavier than RC ewes for autumn live weight (8%), winter live weight (9%), spring live weight (7%), greasy fleece weight (20%) and clean fleece weight (19%). Small but significant (P<0.01) flock differences were found for fibre diameter and yellowness. HF fleeces were coarser and more yellow than RC fleeces. HF ewes were significantly (P<0.01) higher than RC for ovulation rate (1.80 vs 1.73 SED 0.03), number of lambs born/ewes lambed (1.63 vs 1.56 SED 0.02), and number of multiple births/ewes lambed (60% vs 54% SED 2%), but lower (P<0.01) for number of lambs weaned/lambs born (0.84 vs 0.88 SED 0.01). The results indicate that single trait selection for fleece weight enhances greasy and clean fleece weights, live weight and ovulation rate, with an associated increase in FD and yellowness of their fleeces.

Effect of very low sperm doses on pregnancy rates after AI in sheep. - Smith JF; Parr J; Murray GR; Clarke A; Oliver JE; McDonald RM; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1999)
Low sperm numbers and ambient temperature storage are two important factors in the successful AI system for dairy cattle in New Zealand. A critical evaluation of these factors with ram semen is required before the establishment of a similar AI system within the NZ sheep industry is feasible. A trial involving a total of 1262 Romney ewes was conducted in April 1998 to examine the effects of inseminate dose (25, 5, 1 and 0.5 x 106 sperm) of semen held for up to 9 h at 20°C in two diluents (RSD-1 and RSD-8). Ewes, synchronised with 3 types of CIDR devices were laparoscopically AI`ed with semen from either a Finn or a Romney ram at set times (49 or 56h) after CIDR removal. AI was spread over 4 days in each of two consecutive weeks. Rams were used on each alternative day. Ewes were checked for return to service to determine pregnancy. There was a significant (P<0.001) difference between rams in pregnancy rate (Finn =35.6 and Romney =52.5%). There was an effect (P<0.001) of inseminate dose (25 = 55.5 ± 2.6%; 5 = 45.2 ± 2.6%; 1 = 37.2 ± 2.6% and 0.5 = 37.5 ± 2.6%). However there was a suggestion of an overall dose by ram interaction with the Romney semen maintaining higher fertility at lower dose levels. There were no effects of inseminator or of diluent. Time from CIDR removal to oestrus had a significant (P<0.05) effect. Time to onset of oestrus was affected by CIDR type. While there was no overall effect of CIDR type on fertility, there was a significant (P<0.05) interaction between sperm dose and CIDR type. These results indicate that acceptable (>50%) fertility can be achieved with sperm dose rates as low as 1.0x106 if semen quality is satisfactory thus increasing the number of inseminates per ejaculate 20-50 fold. Improved synchrony methods seem imperative to obtaining better fertility from AI.

Effects of ergovaline in endophyte-infected tall fescue on ewe fertility - Kramer R; Keogh R; McDonald MF (Proceedings of the New Zealand Society of Animal Production, 1999)
Ergovaline is one of the major toxins produced in tall fescue and perennial ryegrass pastures infected with wild type endophyte fungi. Animals grazing these pastures often have reduced productivity and in some cases lower reproductive performance. To date very little is known about the effects of ergovaline on sheep and in particular sheep fertility. A trial was conducted consisting of two groups (n = 20) of synchronised, Finnish landrace x Romney 2-tooth ewes. The groups were grazed on either of two lines of endophyte-infected tall fescue, one producing ergovaline (EV+) and the other ergovaline free (EV-) for two weeks and then mated on the treatments. Ovulation rate, conception rate, and numbers of lambs carried were recorded. Levels of serum prolactin and ergovaline in the pasture were determined. Ergovaline levels in the herbage were 3.30 ± 0.60 mg/g and 0mg/g in the EV+ and EV- pastures, respectively. Ewes grazing the EV+ treatment had significantly lower (P<0.05) ovulation rates and number of lambs carried to 90 days of pregnancy than the EV- group. Serum prolactin was significantly (P<0.001) reduced in the EV+ group. These results indicate that similar effects could be exhibited in ewes grazing endophyte-infected perennial ryegrass pastures containing ergovaline and further trials are being undertaken to examine this possibility.

Effects of herbage mass and ewe condition score at lambing on lamb survival and liveweight gain - Lambert MG; Litherland AJ; McLaren PN (Proceedings of the New Zealand Society of Animal Production, 1999)
Scanned, twin-bearing mixed aged ewes (n=1276) were set-stocked (7.5 ± 0.1 ewes ha-1) over the lactation period at either high or low condition score (CS) (2.51 vs 1.52) and high or low herbage mass (HM) (1160 vs 880 kg DM ha-1 ) in an experiment replicated on 5 farms in Wairarapa. Three farms lambed early (27 August to 4 September 1997) and were summer-dry and two lambed later (22 to 27 September 1997) and were summer-wet. High ewe CS may have improved lamb survival (167 vs 150%, P=0.13) through reduction in estimated lamb mortality (17 vs 25%, P<0.01) on late lambing farms where weather conditions were adverse at lambing, but had no effect on early lambing farms where lambing conditions were more favourable. Ewe CS had no effect on either lamb or ewe LWG. High HM may have reduced lamb mortality on early lambing farms (10 vs 14%, P<0.05) where ewes were under greater nutritional stress than on late farms. Additional HM at set-stocking increased lamb LWG up to docking by 11 g d-1 per 100 kg DM ha-1 increase (P<0.03) on early farms but had no effect on late farms. Lamb LWG from docking to weaning was unaffected by set-stocking HM. The overall effect of an increase in set-stocking HM by 100 kg DM ha-1 was to increase lamb weaning weight by 2 kg on early farms. Additional HM at set stocking increased ewe LWG from birth to docking by 33 g d-1 per 100 kg DM ha-1 increase (P<0.001) but decreased LWG from docking to weaning by 18 g d -1 per 100 kg DM ha-1 increase. This response was similar on early and late lambing farms. On early farms there was a net increase in ewe liveweight at weaning of 1.6 kg for each 100 kg DM ha -1 increase in lambing HM.

The effects of stressors on lymphocyte populations and function in lactating dairy cows. - Fisher AD; Verkerk GA; Stevenson RA; Wesselink E; Morrow CJ; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 1999)
Increased stress in animals can lower immune system function and hence decrease resistance to disease. The objectives of the study were to determine the effects of two stressors on lymphocyte function in lactating dairy cows. Jersey cows were allocated to four, 7-day treatments in a 2 x 2 factorial plan. The factors were level of feeding (4% bodyweight vs 3% bodyweight) and lying time (free choice lying vs prevention of lying from 1500 to 0645 h daily). Blood samples collected during the pre-treatment and treatment periods were analysed for in vitro lymphocyte proliferative response and sub-populations. Lymphocyte proliferative response was not affected by feed level or lying time. Only minor changes occurred in lymphocyte sub-populations. Within the fully-fed cows, lying deprivation resulted in a greater proportion of CD8 (suppressor) cells. These data indicate that lymphocyte function in lactating cows may not be compromised by medium term restrictions in feeding and lying, and that any stress-induced decreases in cell-mediated immunity which occur in practice, are the result of more severe, or prolonged, conditions.

The effects of stressors on milk composition in dairy cows. - Verkerk GA; Fisher AD; Morrow CJ; Matthews LR (Proceedings of the New Zealand Society of Animal Production, 1999)
The effects of two stressors (level of feeding: 4% bodyweight, FI, and 3% bodyweight, RI; and altered lying time: free choice, LF, and prevention of lying from 1500 to 0645 h daily, LD) allocated in a 2x2 factorial design on milk yield and composition of Jersey cows (n=32) were studied. Stressors were applied for 7 days following an 8-day pre-treatment period. Composite milk samples were collected at milkings on days 2-3 of pre-treatment and during the last 4 days of treatment. Fat%, milk weight (am, pm and total daily) and mean daily yields of fat, casein, lactose and total milksolids were not affected by treatment. Protein%, protein yield and casein% were lower with RI (protein%: 3.66 and 3.53, sem=0.02, P<0.01; protein yield: 0.54 and 0.50 kg, sem=0.01, P=0.05; casein%: 2.84 and 2.77, sem=0.02, P<0.05 for FI and RI, respectively). There were no significant interactions between treatments. Protein content of milk was reduced by medium-term feed restriction, but lying deprivation had minimal effects.

Embryo and recipient contributions to pregnancy loss following the transfer of cloned embryos derived from foetal and adult somatic cells - McMillan WH (Proceedings of the New Zealand Society of Animal Production, 1999)
The purpose of this paper is to report on the reproductive outcomes following the transfer of cloned bovine embryos produced following somatic cell nuclear transfer. All recipients received two embryos. In Expt 1 (19 recipients), donor cells were derived from a 34 day old female foetus, while adult cows were used as the genetic donors in both Expt 2 (`Lady` from Enderby Island, 38 recipients) and Expt 3 (Elizabeth, a high genetic merit Friesian, 56 recipients). Overall, embryo survival rate to term was 12%, with little affect of experiment. This compares unfavourably with the reported 30-35% survival rate to term in embryos generated using in vitro production procedures without nuclear transfer. Of all transferred embryos, 36% were competent to survive to term. Furthermore, only 36% of the recipients were competent enough to support a pregnancy to term. We conclude that actual embryo survival is lower with nuclear transfer and IVP technology because both embryo and recipient competence is compromised.

Establishment of a farm monitoring scheme for sheep farms - Shaw CA (Proceedings of the New Zealand Society of Animal Production, 1999)
CF2000 (Clutha Farms 2000), and now NZFT2000 (New Zealand farm technology 2000), make big changes in sheep farm management and business skills available to the individual farmer on his own farm in easily understood, easily workable, and low cost form. The basis of management changes has changed from those based on traditional subjective and often anecdotal information, to a management system where decisions are made on factual timely information backed by latest technology and business abilities.

The Evolution of Liveweight Variance in Angus Steers and Strategies for Control. - Pleasants AB; McMillan WH; Barton RA (Proceedings of the New Zealand Society of Animal Production, 1999)
The effect of year of birth and nutritional treatment on liveweight variance in mobs of Angus steers from birth until approximately 30 months-of-age is examined. Significant (P<0.01) differences in liveweight variance at 30 months-of-age were recorded between years. The environment of the calves over the first 20 days of life appeared to affect the development of mob variance, steers which experienced early life on a sawdust pad showing higher variance at 30 months-of-age in liveweight and carcass weight. Restricted nutrition during the first winter of the steer`s life was associated with a significantly (P<0.05) higher variance in 30 month liveweight (standard deviation 24.0 v 37.8kg). Within mob, lower rates of liveweight change were associated with an increase in liveweight variance (r = -0.72). A mathematical model was used to assess the effects of controlled mating strategies on mob variance. Minor improvements were possible. The implications of controlling mob variance for farm quality assurance management is discussed.

Ewe nutrition: decisions to be made with scanning information. - Stevens DR (Proceedings of the New Zealand Society of Animal Production, 1999)
The ultrasonic scanning technology has provided farmers with a useful tool to determine potential lambing percentages well in advance of lambing. This paper outlines ways in which this information can be used to effectively target groups of ewes to maximise feeding efficiency. Underfeeding of the ewe flock can be partly alleviated by the early sales of non-pregnant ewes. Understanding the interactions between body condition and feeding in conjunction with scanning can lessen birthing problems through appropriate feeding regimes. Targeted feeding plans can ensure that both protein and energy needs are met for single, twin and triplet bearing ewes. Feed types such as brassicas, silage and grain can be targeted to specific periods throughout the pregnancy for optimal feed use once parity is known.

Experiences of a pioneer in the commercial sheep pregnancy scanning business - Farmer RJ; Davis GH (Proceedings of the New Zealand Society of Animal Production, 1999)
Since 1991, ultrasonic pregnancy scanning has developed from a tool used initially to identify dry ewes, into one that accurately identifies ewes carrying singles, twins and triplets. The use of scanning to determine litter size has expanded from stud flocks into a large proportion of commercial flocks. Satisfying the demand for pregnancy scanning has in eight years grown into an industry that employs about 90 scanner operators in the South Island during the peak of the season. Scanning is well established as a vital tool for the monitoring and management of breeding ewes.

Factors affecting behaviour, bruising and pHu in a deer slaughter premises - Pollard JC; Stevenson-Barry JM; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 1999)
Data from an on-going study at a deer slaughter premises were analysed. Over one year 3856 deer, primarily red x wapiti hybrids, from 101 farms were observed. During overnight lairage a mean of 14 (s.d. 7.6) antagonistic encounters/hr occurred. In the race immediately prior to stunning, rearing was the most common form of unsettled behaviour (17% of deer). The incidence of unsettled behaviour differed between carriers (P<0.001). Bruising occurred in 24% of carcasses, increased with load size (P<0.01) and poor weather conditions (P<0.05), and differed between carriers (P<0.05). Half (48%) of all bruises were small and less than 5mm deep. Mean ultimate pH (pHu) was 5.65 (s.d. 0.139), and moderate-high pHu (>5.8) was prevalent in the shoulder (18.5% of carcasses) followed by the loin (10.6%) then the leg (5.6%). Behaviour, bruising and pHu all differed significantly between farms and days (P<0.001).

Farm and Flock Monitoring - Introduction - Davis GH (Proceedings of the New Zealand Society of Animal Production, 1999)
in recent years, sheep farmers have embraced farm and flock monitoring as techniques to increase the profit-ability of their business. Clutha Farms 2000 (CF 2000) was established in South Otago to enable sheep farmers to monitor the performance of their farms. The standard re-cording format applied to each members farm has been the basis of benchmarking, whereby each member can com-pare their farms performance against that of other mem-bers farming in a similar environment. The early success of the scheme has encouraged other regions to set up simi-lar schemes and an umbrella organisation, FT 2000, has been formed to co-ordinate and encourage new groups throughout New Zealand. Ultrasonic pregnancy scanning as a quick and reli-able technique for identifying the number of foetuses car-ried by each ewe has opened new opportunities for the management of breeding flocks. The ability to separate mobs of ewes according to their pregnancy status has al-lowed farmers to run multiple-bearing ewes with greater confidence. Pregnancy scanning has also improved the monitoring of flock performance by highlighting losses between mid-pregnancy and tailing. For farmers who were previously unaware of the magnitude of their neonatal lamb mortality, the capacity to accurately measure this loss has motivated them to make greater effort to improve lamb sur-vival. An index relating scanning percentage to mating liveweight has been a useful basis for benchmarking flock prolificacy. This contract draws on the experiences of those who had a pioneering role in establishing farm and flock moni-toring, those who in various ways provide monitoring serv-ices, and farmers who use and benefit from monitoring. In keeping with the location of this years annual conference, the contract has a heavy southern bias, but as farm and flock monitoring are becoming increasingly available through-out New Zealand there is the potential to significantly im-prove the production and profitability of the entire sheep industry.

Farm financial monitoring - Johnstone WJ (Proceedings of the New Zealand Society of Animal Production, 1999)
The financial data gathered by Shand Thomson & Co has highlighted the gap between the average and the top 10% or top 25% of farmers. The sharing of this information among farmers helps individuals identify the strengths and weakness of their usiness and is an important step in making the changes required to increase profitability.

Farm of origin and finishing environment effects on beef quality attributes - Smith DR; Smith NB; Muir PD (Proceedings of the New Zealand Society of Animal Production, 1999)
An experiment was conducted to test the hypothesis that finishing environment can affect beef quality attributes, including fat and meat colour, meat pH, subcutaneous fat depth (FD) and intramuscular fat (IMF) content of pasture-fed beef. 181 rising 2-year old Angus steers were obtained from 4 source farms and finished at 4 North Island locations. On 3 properties, home-bred cattle were compared to a common control line. On a fourth property, cattle from the 3 sources were compared to each other and to the control. FD, meat pH and meat colour were affected by location (P<0.01), but not source. Only source effects were significant (P<0.05) for IMF. Both source and location affected fat colour (P<0.01). Steers that were killed later had significantly (P<0.01) higher meat pH (r=0.33), darker meat (r=-0.24), greater IMF (r=0.26), higher plasma carotene levels at slaughter (r=0.38) and yellower fat b* (r=0.39). The results indicate that both farm of origin and finishing environment can affect meat quality. Both sources of variation appeared to be mediated, in part, by cattle growth rate.

Farm performance measurement - Linking monitoring to business strategy - Parker W (Proceedings of the New Zealand Society of Animal Production, 1999)
Farm monitoring and evaluation are elements within the control function of management. Control is directly linked to planning: through planning performance, targets are set and outcomes are measured and assessed relative to these. The use of formal monitoring by farmers has been lower than expected. To redress this, more emphasis is now being placed on tying farm performance measures (or indicators) to business strategy. The aim is to transparently connect day-to-day (operational) management to the goals of the manager/ owner. This shift in the focus of farm monitoring and evaluation concentrates performance measurement around a limited number of factors that are critical to the successful execution of strategy. Data collection and analysis is therefore directly integrated with adding value to the farm business. It also facilitates the correct application of benchmarking to continually improve performance through farmer learning. The balanced scorecard provides a mechanism to integrate farm monitoring results with farm mission, strategy and target performance in a condensed and easy to read format. This should further encourage farmers to monitor and benchmark their production and management systems in order to gain feedback for evaluating decisions (learning) and help them to continually update their strategy to sustain high performance.

Farmer experience of farm monitoring - Miller JR; Miller GL (Proceedings of the New Zealand Society of Animal Production, 1999)
Farm monitoring has played a key role in the dramatic increase in our farm production since 1995/96. Through farm monitoring we are now much more aware of the current performance levels of our flock. The basis for decision making has been greatly improved by having more factual information on livestock performance. Androvax and crossbreeding have been identified as the means to rapidly improve our lamb production

Farmer use and experience of ultrasonic pregnancy scanning - McAtamney TJ; McAtamney S (Proceedings of the New Zealand Society of Animal Production, 1999)
Ultrasonic pregnancy scanning has enabled better feed allocation and lambing management of our breeding flock. In the past two years, scanning has also identified many of the triplet-bearing ewes but there is a need to develop more effective systems for managing these ewes. We attribute much of the 18% increase in lambing percentage over the past four years to improved management based on scanning results. Scanning also has benefits in the genetic improvement of the flock and we envisage in the near future selecting all replacements from twin-bearing and triplet-bearing ewes that have lambed as hoggets and subsequently never had more than one single birth.

Fertility control of possums: The search for regulators of gonadal development and pituitary function - Eckery DC; Fidler AE; Moore LG; McNatty KP (Proceedings of the New Zealand Society of Animal Production, 1999)
The Possum Research Programme of the Reproductive Biology Group at the Wallaceville Animal Research Centre is focused in four specific areas, namely: (a) identifying growth factors and hormones associated with gonadal development during the first 200 days of life; (b) searching for possum homologues of a riboflavin carrier protein (RCP) and a gut epithelial receptor/transporter protein (FcRn); (c) elucidating the role of gonadotrophin-releasing hormone (GnRH) on pituitary gonadotrophin secretions and; (d) producing and testing reagents which might interfere with gonadal formation and function of the pituitary gland. Possum specific reagents and in vitro test systems have been developed and will be used to develop strategies for fertility control.

Field data analysis of lamb survival and mortality rates occurring between pregnancy scanning and weaning - Nicoll GB; Dodds KG; Alderton MJ (Proceedings of the New Zealand Society of Animal Production, 1999)
Ultrasonic scanning for pregnancy diagnosis in commercial sheep flocks has highlighted the magnitude of lamb loss from scanning to docking or weaning. From seven ram breeding flocks in Landcorp Farming Limited, lamb survival rates were derived from the number of lambs per ewe present at six stages: pregnancy scanning, birth, born alive, 48h after birth, end of lambing and weaning. Differences in lamb survival rates between adjacent stages provided the mortality rates for five intervals: pregnancy scanning-birth; birth-born alive; born alive-48h after birth; 48h after birth-end of lambing; end of lambing-weaning. Flock-year affected lamb survival rate at all stages (P<0.001) but varied with ewe age and lamb birth/rearing rank (P<0.001). Mean lamb survival rates for 3- and 4-year-old dams were generally higher than those of other dam age groups. Triplet-reared lambs had consistently lower survival rates than single- or twin-reared lambs (P<0.001). Lamb mortality rates for the five intervals were 0.03, 0.08, 0.03, 0.03 and 0.04 lambs per potential lamb at scanning, respectively. Lamb mortality was highest at birth, with lower survival rate of triplet-born lambs compared with single- and twin-born lambs (0.82±0.006 vs 0.93±0.004 and 0.93±0.002 lambs per potential lamb respectively; P<0.001). The results indicated when, and to what extent, lamb losses occurred in the field between pregnancy scanning and weaning, and the importance of applying appropriate ewe/lamb feeding and management policies to minimise lamb mortality rates.

Fleece production patterns in Romney ewes: Effects of photoperiod, pregnancy and lactation - Pearson AJ; Kendall PE; Ashby MG; Wildermoth JE (Proceedings of the New Zealand Society of Animal Production, 1999)
Twenty one Romney ewes were housed indoors for 12 months from February to determine the effect of season, pregnancy and lactation on wool growth. Ten ewes were naturally mated in April to lamb in September. The ewes were fed to maintain constant maternal body weight and a midside patch harvested monthly to determine clean fleece growth rates. An effect of pregnancy on individual fibre length growth rate, determined by autoradiography, occurred as early as 21-35 days after joining. During the second month of gestation, fleece production and mean fibre diameter fell below that of non-pregnant ewes and continued to diverge until parturition. Wool production rose in the non-pregnant group from August, but did not increase in lambing ewes until after parturition. These data suggest that pregnancy is associated with an early hormonally-mediated depression in follicle output superimposed on the decline associated with winter photoperiod.

The future for the N.Z. Society of Animal Production - Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1999)
Genetics is the study of inheritance, and animal breeding is the application of knowledge in genetics to achieve improvement. In the context of animal breeding, a systematic framework (Harris et al., 1984) is typically employed to design improved breeding programmes. The steps involved in this systematic framework include the following. 1.Define the goal of the business. 2. Identify the list of traits that influence the goal. 3.Determine the relative (economic) importance of the traits in the list. 4.Measure those characteristics that allow individuals to be ranked then selected (or culled) in terms of their contribution to progress towards the goal. 5.Make preferential use of superior individuals as parents of the next generation

Genetic effects in GrowBulk sheep - Clarke JN; Sumner RMW; Cullen NG (Proceedings of the New Zealand Society of Animal Production, 1999)
GrowBulk sheep are a strain of long-wool type sheep growing high bulk wool developed by introgressing high-bulk genes from Texel and Dorset rams into Romney ewes. Progeny selection was planned to minimise decreases in clean fleece weight. Rams have been released to four multiplier flocks. Genetic effects were evaluated in the nucleus and multiplier flocks using a restricted maximum likelihood animal model. Heritability estimates were 0.46±0.05 for bulk and 0.30±0.05 for clean fleece weight with a genetic correlation of -0.48±0.09. The crossbred genotypes represented in the nucleus flock showed a range in average breeding merit for bulk of 27 to 31 cm³/g, their weighted mean genetic superiority over contemporaneous Romneys being 5.3 cm³ /g. The first crop of commercial progeny by rams from this flock showed an average genetic superiority in bulk over their dams of approximately 4 cm³/g. Genetic trends indicate that selection has been able to maintain the bulk advantage of the crossbreds while at the same time improving their fleece weight.

Genetic parameter estimates for lamb survival in Romney sheep - Lopez-Villalobos N; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1999)
Lamb survival is a trait of economic importance in sheep production. Most lamb losses occur within 1 to 2 days of birth. Losses may be attributed to the lamb and to the behaviour of the dam. Maternal effects are environmental for the offspring but are genetic for the dam. ANIMALPLAN has separately evaluated individual and maternal attributes. Difficulties arise to genetically evaluate animals for survival because this trait has a binomial distribution whereas most analytical procedures assume normality. The objective of this study was to estimate heritabilities and genetic correlations for direct and maternal genetic effects on two underlying scales (probit and logit) for lamb survival in order to implement a new procedure of genetic evaluation. Variance components were obtained by Restricted Maximum Likelihood (REML) procedures after logit or probit transformation of the data with a linear mixed model using records from 25,874 lambs born over the period 1989 to 1995 in a prolific Romney flock. The lambs were the progeny of 218 sires and 6,771 dams. The model included fixed effects of sex, year, litter size at birth and age of dam and the random effects for direct genetic, maternal genetic and maternal environmental influences. Lambing and survival percentages were 178% and 87%, respectively. The estimates of heritability on the logit scale were 0.01, 0.03 and 0.04 for direct, maternal and total genetic effects, respectively. The proportion of total variance explained by maternal environmental influences was 0.09. The estimated genetic correlation between direct and maternal genetic effects was - 0.26. Similar estimates were obtained on the probit scale. Estimates will be lower for the observed scale. These results indicate a greater opportunity for improving survival by manipulating the environment rather than by selection. However survival analysis is an important component of quality assurance in a genetic improvement scheme.

Genetic progress in a Romney Group Breeding Scheme - Morris CA; Amyes NC; Hickey SM (Proceedings of the New Zealand Society of Animal Production, 1999)
The Auckland Romney Development Group was established in 1968 and its aims continue to be to test and select rams for Group Members, and to breed rams for sale under conditions relevant to farming in the greater Auckland district. Breeding objectives include increased litter size (NLB), weaning weight (WWT), yearling live weight (YLW), yearling greasy fleece weight (YFW), and also increased facial eczema (FE) tolerance. Each year until 1993, members received selected nucleus-bred 15-month rams for use at home, and the next cut of nucleus rams and some elite homebred rams were offered as breeding stock for sale. From 1993, restricted maximum likelihood methods were introduced to calculate breeding values, and across-age ram selection was applied. At the same time, the nucleus ewes were re-distributed across all Members` flocks, and between-flock and between-year genetic links were maintained by movement of sires for mating. Estimates of total genetic progress by birth-year (obtaining data from Animalplan files, which were only available from 1986) were: WWT (1986-97) 1.83±0.17 kg (7.8% of the mean), YLW 2.76±0.24 kg (6.4%), YFW 0.23±0.01 kg (7.3%) and NLB (1986-95) 0.029±0.015 lambs (1.8%), and all flocks have contributed to the long-term genetic changes. Annual genetic trends over the period were approximately linear, except for YLW which appeared to show an increasing response rate. This is probably related to the extensive progeny testing carried out since 1994 to study sire families which appear to be elite for YLW, using progeny-test matings of rams to outside tester ewes. Segregation tests for a possible major gene have been carried out. Some evidence of bimodal distributions for YLW within sire was found, with a gene whose effect was +9% of the mean, in heterozygotes. Since 1993, secondary selection decisions based on FE have been complicated by across-flock selection, but genetic progress for this trait appears to be linear, with a heritability estimate for log (gamma glutamyltransferase; GGT) of 0.34±0.09. Over the birth years 1981-1997 there was genetic change in GGT by a factor of 0.71 (29% improvement), compared with a factor of 0.30 (70% improvement) over the same time period in the single-trait FE selection lines at Ruakura (Resistant versus Control lines).

A genetic test to identify carriers of the ovine Inverdale fecundity gene - Galloway SM; Cambridge LM; Henry HM; Van Stijn TC; Davis GH (Proceedings of the New Zealand Society of Animal Production, 1999)
The Inverdale high fecundity gene (FecXI ) is carried on the sheep X-chromosome. This provides a convenient means of producing prolific single copy carrier ewes because all daughters of a carrier ram will inherit the gene. A single copy of the gene increases litter size by about 0.6 lambs per ewe lambing. However, ewes homozygous for the gene are infertile. Production of elite rams that carry the gene requires the ability to distinguish between non-carrier and single copy carrier animals. Three DNA markers flanking the gene in a 10 cM (centiMorgan) region have been used to develop a genetic test that can identify single and double copy carriers in most cases. The test relies on detecting inheritance of the Inverdale region of the X-chromosome in offspring of known carriers. Validity of the genetic test has been confirmed by progeny testing of rams and laparoscopy of ewes. The test has recently been adapted to DNA obtained from a few plucked wool follicles.

Has Rabbit Haemorrhagic Disease worked in New Zealand - Parkes J; Norbury G; Heyward R (Proceedings of the New Zealand Society of Animal Production, 1999)
This paper reports on some results of a field study of Rabbit Haemorrhagic Disease (RHD) since its illegal release in New Zealand in August 1997. The presence of fresh carcasses and seropositive rabbits of different ages were used to indicate the presence of RHD in rabbit populations, and changes in rabbit densities were used to infer its efficacy.Serological evidence from two Otago study sites where rabbits were sampled before and five times after the initial epidemic shows that (a) biociding left more seropositive, and so immunised, adult survivors than were left after a natural epidemic; thus natural epidemics are best if they persist, (b) the proportion of seropositive rabbits in cross-sectional samples declined over the 6 months after the initial epidemic, and (c) a second epidemic of RHD broke out naturally at both sites in September 1998. At 36 study sites around New Zealand, the initial 1997 epidemics caused declines in rabbit densities averaging 32±23 % (95% S.E.) in the North Island and 56±23% in the South Island. However, success was not universal and rabbits increased at a few sites.Causes of failure at some sites have been attributed to poor-quality biociding where rabbits were vaccinated rather than infected.Variable kills were also seen in natural epidemics at sites where the initial rabbit densities were less than c. 25 rabbits seen /spotlight km, while consistently high kills were evident at intial densities above this threshold. Overall, rabbit numbers increased at most sites measured between winter 1998 and early 1999, despite second epidemics being confirmed at some of these sites. The optimal strategy to manage rabbits as pests of pastoral production in New Zealand cannot be determined because we cannot yet predict the behaviour of RHD, and we have insufficient information on the relationships between rabbit densities and their impacts on production, although a single unreplicated trial we did in Otago showed that the reduction in rabbit numbers due to RHD reduced the grazing impacts of rabbits by 77%. Therefore, in the absence of any robust measure of benefits we cannot judge how much it is worth spending on conventional control. These information gaps are hindered by the old paradigm of rabbit control knock them down and hold them down. If this strategy was ever the best for a boom-bust pest, it is certainly not so now that a biological control agent is at least partially successful and persistent.

Hogget wool traits of sheep breeds being used for crossbreeding with strong wool breeds - preliminary estimates from research studies - Bray AR (Proceedings of the New Zealand Society of Animal Production, 1999)
Average fleece weight and wool quality characteristics for pure breeds were calculated from comparisons of pure breeds and crossbreeds with strong wool sheep in fifteen studies. The results for each breed reflect the sample of the breed selected for the studies, after removal of environment effects. Compared to the average Romney, fibre diameter was markedly lower in Merino (59% of Romney, P<0.001) and Finn (72%, P<0.001) but was not significantly different in Texel, Poll Dorset and East Friesian sheep. Staple lengths of other breeds were 53 to 77% (P<0.05) of Romney values. Wool bulk was greater in Texel and Poll Dorset (both 49%, P<0.001), and Merino (32%, P<0.01). To provide a better basis for predicting effects of crossbreeding in breeding ewe flocks, more information is needed from the East Friesian breed. Also the observations need to be extended to adult ewes and need to be obtained from wider samples of the breeds and sheep farming environments, and account needs to be taken of heterosis and other effects.

The importance of date of birth records in genetic evaluation of deer - Amer P; Garrick D; Nicoll G (Proceedings of the New Zealand Society of Animal Production, 1999)
This paper addresses one particular difficulty associated with performance recording and genetic evaluation of deer, that is, the problem of recording pedigrees. A deterministic simulation was carried out using parameters based on deer populations where birthday has been recorded. For weaning weight, failure to record birth date resulted in reductions by 29% and 19% in selection accuracy, with selection on the records from the individual or from 20 progeny respectively. Corresponding reductions for yearling weight were 11% and 5% respectively. It was concluded that while genetic progress in deer will be compromised by lack of date of birth records, selection for growth traits can still be effective.

Improving lamb birth weight through mid-to-late-pregnancy shearing: a review of recent studies - Kenyon PR; Morris ST; Revell DK; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1999)
A series of five experiments have been conducted at Massey University to determine whether mid- to late-pregnancy shearing of ewes might provide an opportunity to increase lamb birthweights and enhance survival, particularly of multiple-born lambs, under New Zealand`s pastoral conditions. Although birthweight responses were seen in most studies, they were not consistent with respect to the magnitude of the response or its occurrence in singles vs twins. However, when comparison was made across studies there was a strongly negative relationship between the size of the response and the birthweights of control lambs (those from unshorn ewes). We conclude that responses to mid- to late-pregnancy shearing are likely to be greatest when fetal growth in unshorn ewes is limited by maternal constraint.

Incidence of high pH in venison: Implications for quality - Stevenson-Barry JM; Carseldine WJ; Duncan SJ; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 1999)
Muscle ultimate pH (pHu) is known to influence eating quality, functional properties and safety in beef, lamb and pork. The extent to which muscle pH affects tenderness and the extent to which it can be `aged` out is different for lamb compared to beef and two studies have been carried out with venison in order to determine the implications for venison tenderness. Longissimus thoracis et lumborum (striploin) muscles from nine carcasses which went prematurely into rigor (`stiff` carcasses) had higher mean pH than muscles from nine control carcasses (5.93 vs 5.61, SED = 0.091 at 2 days postmortem (PM); 5.83 vs 5.56, SED = 0.100 at 7 days PM; 5.81 vs 5.54, SED = 0.096 at 21 days PM). A typical quadratic relationship was observed between tenderness and pH which explained non-significant differences in tenderness between the stiff and control muscles. The tenderness-pH relationship for venison striploins assessed at 2 days after slaughter was typical of that reported for unaged beef and lamb in that muscles with pH in the range of 5.8-6.2 were tougher (P< 0.05) than normal (5.5-5.7) and high (>6.2) pH muscles. The tenderness profile change after 7 and 21 days chilled storage at 4°C was similar to that reported for lamb in that all of the striploin samples tenderised to an acceptable level. Ten intermediate pH (5.8-6.2) biceps femoris (BF) muscles were tougher (P< 0.05) than ten normal pH (5.5-5.7) muscles at all times with chilled storage at 0°C for up to 6 weeks. The intermediate pH muscles that were frozen then thawed prior to assessment were significantly more tender than the chilled intermediate pH muscles, but still tended to be tougher than the normal pH muscles. Both the chilled and frozen intermediate pH muscles were significantly more variable in tenderness than the normal pH BFs.

Increasing milksolids production with supplementary feeds - Penno JW; McGrath JM; MacDonald KA; Coulter M; Lancaster JAS (Proceedings of the New Zealand Society of Animal Production, 1999)
Four farmlets were established at a stocking rate of 4.41 Friesian cows per hectare to compare rolled maize grain, maize silage and a nutritionally balanced ration as supplementary feeds for grazing dairy cows, for three complete seasons. Supplements were offered whenever it was estimated the herds were eating less than 15 kg DM/cow/day or were leaving a post-grazing residual herbage mass of less than 1800 kg DM/ha. Offering 1.3 to 1.5t DM/cow/year of supplement increased net herbage accumulation from 18.3 to 19.2 t DM/ha, however, this did not result in higher annual herbage intake. The use of rolled maize grain, maize silage, and balanced ration supplements increased production from 1188 kg milksolids (MS)/ha to 1763, 1602, and 1769 (±69.6) kg MS/ha/year, with responses of 98, 77, and 99 g MS/kg DM, respectively. The magnitude of the response to the supplementary feed was directly proportional to the increase in metabolisable energy supplied by the supplement. Full lactation responses to supplementary feeds were two fold greater than those measured in short term feeding trials. Responses of 7.5g MS/MJME can be expected over the complete lactation when supplements are offered to dairy cows grazing restricted pasture.

Lack of effect of short term chromium supplementation in lactating Jersey cows - Back PJ; Lee J; MacKenzie DDS; Davis SR; Harris PM (Proceedings of the New Zealand Society of Animal Production, 1999)
The responses of dairy cattle to chromium (Cr) supplementation reported in the literature suggest that it has the potential to reduce the incidence of both mastitis and ketosis. The effect of Cr supplementation of pasture fed dairy cows in early lactation was studied. Ten lactating Jersey cows fitted with rumen fistula were infused with either Cr-yeast (n=4), casein (n=3) or buffer only (controls; n=3) directly into the abomasum. All cows were subjected to a hyperinsulinaemic euglycaemic clamp. Preliminary results show that there was no effect of Cr supplementation on milk yield, cortisol and b-hydroxy butyrate concentrations and somatic cell counts.

Marker-assisted Selection for Meat Quality and the Ovine Calpastatin Gene - Palmer BR; Morton JD; Roberts N; Ilian MA; Bickerstaffe R (Proceedings of the New Zealand Society of Animal Production, 1999)
The calpain-calpastatin system (CCS) comprises a family of calcium-dependent neutral proteases, the calpains, and calpastatin, a specific inhibitor of the calpains that regulates their activity in vivo. The CCS is found in most animal tissues and influences many important processes including muscle development and degeneration, meat tenderisation postmortem, cataract formation and fertility. The calpains have been shown to play the major role in postmortem tenderisation in beef, lamb and pork by degrading specific muscle structural proteins. The level of calpastatin immediately postmortem appears critical in determining the ultimate tenderness of aging muscles. Tenderness has been shown in consumer surveys and tasting panel tests to be the most important characteristic determining the overall eating quality of meat. In using a molecular genetic approach to studying meat quality in sheep we have chosen the ovine calpastatin gene (CAST) as a candidate gene for meat quality. We have described a three allele system of polymorphic variants (CAST a, b and c) in a region of the ovine CAST. Since 1995 we have carried out slaughter trials on small groups of Dorset Down hoggets and Dorset Down x Coopworth lambs to ascertain any association between meat quality traits and the molecular markers in CAST. Sheep with the genotypes of CAST aa, ab and ac were compared. These trials indicate an association of the CAST genotype ac with increased liveweight gain (+12-17%,p >0.05), increased age-corrected carcass weight (+15-18%, p>0.05), but also increased longissimus dorsi shear force (+4-12%, nonsignificant) compared to sheep with the CAST genotype aa.

A methodology for dealing with uncertain outcomes when applying embryo technologies - McMillan WH; Vivanco HW (Proceedings of the New Zealand Society of Animal Production, 1999)
High variability in number of embryos collected per donor has implications when programming recipients for `fresh` embryo transfer because decisions on the number of recipients required need to be made prior to collecting embryos. This paper describes a methodology for dealing with these uncertainties. The distribution of number of transferable quality embryos per donor was determined and conformed to a Poisson distribution. The distribution of the proportion of recipients that are suitable for transfer was assumed to be binomial. The model determined recipient numbers under 4 contrasting risk scenarios, and compared these with a simple arithmetic approach. The simple arithmetic approach is likely to expose programmes to high levels of risk. The proposed methodology enables practitioners to programme the number of recipients that is consistent with any level of risk they are prepared to take in having surplus embryos or recipients. The model could be extended to provide economic or utility maximisation endpoints.

Milk production and production worth of anoestrous dairy cows compared with their cycling herd mates - Rhodes FM; Morgan S (Proceedings of the New Zealand Society of Animal Production, 1999)
The primary aim of this study was to determine whether the milk production and production worth (PW) of anoestrous (AA) cows differed from that of their cycling (CYC) herd mates. In addition, a pilot survey was carried out to examine between herd factors, which may influence the percentage of cows diagnosed anoestrous. Individual production records were collated from 7786 cows in 26 herds, in which AA cows were identified following veterinary examination seven days before the planned start of mating. Milk production and PW did not differ between AA and CYC cows, after adjusting for herd, age and days in milk (P>0.05). The percentage of cows diagnosed AA varied from 13.4% to 51.5% among herds. Completed questionnaires were obtained from 19 herd owners regarding management factors in these herds. Stocking rates were higher in herds with a low percentage of anoestrous cows (<30%AA) compared with those with a high percentage (≥30%AA; p=0.05), but level of supplementary feeding was higher in herds with a low level of anoestrous (p=0.01). It is concluded that milk production and PW do not differ between AA and CYC cows. Nutritional supplementation after calving may influence the percentage of a herd still anoestrus before the start of mating.

Milk production from perennial ryegrass pastures containing different levels of endophyte - Clark DA; Thom ER; Waugh CD; Burggraaf VT (Proceedings of the New Zealand Society of Animal Production, 1999)
These experiments aimed to compare milk production in spring and autumn from perennial ryegrass pastures containing either low (L) (<10%) or high (H) levels of endophyte infection at two pasture allowances. In October 1997 milk yield was higher (P<0.05) from L compared with H endophyte (15.1 v 14.4 kg/cow/day), similarly for fat yield (0.95 v 0.9 kg/cow/day), and milksolids (MS) (1.53 v 1.46 kg/cow/day), but not protein yield. In October 1998 there was no effect of endophyte level on milk, fat, protein and MS yield. In March 1998 milk yield was higher (P<0.001) from H compared to L endophyte (8.5 v 7.4 kg/cow/day), similarly for fat yield (0.53 v 0.48 kg/cow/day), protein yield (0.35 v 0.34 kg/cow/day) and MS yield (0.89 v 0.81 kg/cow/day). No carryover effects were recorded on milk yield or composition in any period.

Milk production response to replacement of carbohydrate with lipid and the addition of ruminally protected protein - Thomson NA (Proceedings of the New Zealand Society of Animal Production, 1999)
Cows grazing a restricted pasture allowance of 25 kg DM/cow/day during November (75 days in milk) were offered five supplementary feeds in a factorial experiment. The supplements were isoenergenic supplying an additional 68 MJME/cow/day but varied in whether the energy source was lipid or carbhydrate (rapeseed vs maize), crushed or whole rapeseed (cruide protein (CP), 20.6%), or with and without ruminally protected protein (formaldehyde treated sunflower meal, 37.8% CP). The CP contents of the pasture and the maize supplement were 14.7% and 9% respectively giving an average CP of the feed consumed of 13%. Cows on the control treatment supplemented with maize grain produced means of 10.5 l/d of milk, 0.61 kg/d fat, 0.43 kg/d of protein and 1.03 kg/d of milksolids. Partial replacement of maize with 20 MJME/cow/day of rapeseed (CP of supplement, 11.8%) increased daily milk (9.3%), fat (8.6%), protein (4.4%) and milksolids (6.9%) yields. Crushed rapeseed resulted in twice the yield increase as whole rapeseed. Additional replacement of maize with 13 MJME/cow/day of ruminally protected protein (CPO of supplement 18%) resulted in further increases of 15.9%, 16%, 17.4% and 16.8% for milk, fat, protein and milksolids respectively. The response to ruminally protected protein was greater when incorporated with maize/crushed rapeseed than maize/whole rapeseed. Crushed rapeseed depressed fat and protein content in milk. Other supplements had no effect on fat, protein or lactose contents. Replacement of maize with crushed rapeseed and ruminally protected protein increased yields of milk (36.1%), fat (32.9%), protein (23.5%) and milksolids (31.8%) compared to maize alone. For cows 75 days in milk the results demonstrated that a dairy ration comprising 13-14% CP provided insufficient protein to sustain full milk production.

Milking performance of East Friesian Poll Dorset cross ewe hoggets - Newman S-AN; Stieffel W (Proceedings of the New Zealand Society of Animal Production, 1999)
The milking performance of East Friesian Poll Dorset cross and Poll Dorset hoggets in a commercial milking system was studied at Flock House Agricultural Centre. Hoggets were milked twice daily from 2-4 days post-lambing on a 30 bale rotary platform for about 102 days. Live weight of the Poll Dorset and East Friesian cross hoggets were similar (P>0.05), both groups increased in weight from 51.5 ± 0.7 to 61.8 ± 0.8 kg over the trial period. Mean daily milk yield of the East Friesian cross hoggets was significantly higher (P<0.01) than for the Poll Dorset hoggets, 1.13 ± 0.06 and 0.87 ± 0.08 l/ewe/day, respectively. Milk production of the East Friesian cross hoggets over the lactation period was 30% higher in milk volume (113.1 ± 6.0 versus 86.8 ± 7.9 l/ewe) but had a lower milk solids content (18.19 ± 0.06 versus 18.48 ± 0.07 %) resulting in a 25% higher yield of milk solids (204 ± 3 versus 164 ± 4 g/ewe/ day) than Poll Dorset hoggets.

Monitoring oestrus and ovulation in brushtail possums - McLeod BJ; Thompson EG; Crawford JL; Mahoney PM; Eckery D (Proceedings of the New Zealand Society of Animal Production, 1999)
The time of ovulation following removal of pouch young (RPY) was determined in 240 possums by repeated laparoscopic observation of the ovaries, and in a subset of these animals (n=20) also from changes in vaginal mucus. In a separate experiment (n=18), the time of oestrus was estimated from an influx of epithelial cells and leucocytes in urine, and confirmed by mating and hormonal data. A preovulatory follicle was observed at laparoscopy in all animals that ovulated (n=138), but not in any that did not (n=102). An influx of neutrophils in vaginal mucus occurred in 12/20 possums, including 4 that failed to ovulate. An increase in epithelial cells in urine was observed in 9/12 possums that exhibited an LH surge. However, this change occurred after the time of the preovulatory LH surge in 6 of those animals and peak cell numbers varied widely between all animals. These studies confirm that although changes in the cell content of mucus and urine can retrospectively define stage of the oestrous cycle, they are of little value for predicting impending oestrus, the LH surge or ovulation

Mouse 3T3-L1 Fibroblast Cells as a Bioassay For Serum-Borne Adipogenic Factors - Veenvliet BA; Littlejohn RP; Suttie JM; Broad TE (Proceedings of the New Zealand Society of Animal Production, 1999)
This study of the development of adipose tissue in sheep set out to investigate whether culture medium containing serum from Coopworth lean and fat selection lines had differential effects on proliferation and differentiation of mouse 3T3-L1 preadipocytes. Using fetal calf serum (FCS) as a positive control, the effects of serum from lean and fat lines of sheep and from goat and horse were compared by analysing total cell numbers, and protein and triglyceride (TG) levels per unit DNA in the mouse cell cultures. Differentiation was induced in all serum treatments. Mean cell numbers in cultures up to 13 days after differentiation were higher for sheep serum than for the other species (P<0.001). There was no significant difference (P>0.05) in protein content between FCS and serum from lean and fat sheep lines. Mean TG levels were significantly higher (P<0.001) for FCS than for the lean and fat selection lines, which did not differ significantly from each other (P>0.05). Significant differences in either proliferation or differentiation were not detected between the fat and lean sheep.

Nutritional effects, in early pregnancy, on lamb production of Finnish Landrace x Romney ewes - Smeaton DC; Webby RW; Tarbotton I (Proceedings of the New Zealand Society of Animal Production, 1999)
This study tested the hypothesis that in high fertility ewes, low nutrition in early to mid pregnancy could affect placental development in turn affecting foetal development, lamb birth weight and lamb survival. In 1997, 600 Finn x Romney ewes were randomised to 1 of 5 herbage allowance treatments applied over day 20 to 70 of pregnancy. Over the treatment period, mean herbage intake ranged from 0.69 to 2.04 kg DM/ewe/day resulting in ewe live weight changes of 36 to +60 g/ewe/day respectively (p<0.001). The result was a consistent but non-significant trend in birth weight with the lowest allowance ewes having single and twin lamb birth weights of 5.2 and 4.3 (SED 0.2) kg respectively. Corresponding birth weights for lambs from the highest allowance ewes were 5.3 and 4.4 kg. Lambing rate and lamb survival were not affected. In 1998, 4 nutrition treatments were applied from day 7 to 70 of pregnancy to 650 ewes randomised from either of 2 reviously generated mating weight groups. These treatments gave live weight changes of 84 to +35 g/ewe/day (p<0.001) from average herbage intakes of 0.70 to 1.96 kg DM/ewe/day. Birth weight of the single lambs (trial average 5.0 kg; SED 0.1) was not affected. However, twin lambs born from ewes from the lowest herbage allowance treatment were 0.35 kg lighter than those from the other treatments (p<0.01). Similarly, lambs born per ewes mated and lambs weaned per ewes present at lambing were also affected (p<0.05). We conclude that, in fecund ewes, nutrition in early pregnancy can affect twin lamb birth weight and lambing rate but only where the ewes are losing weight at more than 40 g/ewe/day or lose more than 4 kg from mating to mid-pregnancy.

Pasture digestion in response to changes in ruminal pH - de Veth MJ; Kolver ES (Proceedings of the New Zealand Society of Animal Production, 1999)
Four continuous culture fermenters were used to determine the ruminal pH required for the optimal digestion of pasture. Spring pasture was fermented at four controlled levels of ruminal pH (5.4, 5.8, 6.2 and 6.6) according to a 4x4 Latin square design. Decreasing pH from 6.6 to 5.4 reduced dry matter digestion by 14%, neutral detergent fibre digestion by 11%, total non-structural carbohydrate digestion by 5% and microbial nitrogen flow by 18%. A quadratic relationship was observed between ruminal pH and the true ruminal digestibility of dry matter (R²=0.94, SE=2.06) and microbial nitrogen flow (R²=0.66, SE=0.05). The ruminal digestibility of pasture dry matter was optimised at pH 6.35, and synthesis of microbial protein was optimised at pH 6.13. This experiment indicated that digestion was largely insensitive to pH across a broad range of pH (5.8 to 6.6), but that a large reduction in digestion occurred when mean pH was less than 5.8.

Performance of dairy cows grazing pastures with or without ergovaline and lolitrem B in Northland. - Keogh RG; Blackwell M; Shepherd P (Proceedings of the New Zealand Society of Animal Production, 1999)
Ergovaline and lolitrem B are alkaloids produced by Neotyphodium endophytes in ryegrass. These toxins are associated with poor animal performance in many situations but influences on milk production by dairy cows had not been determined in NZ except for short-term trials. An on-farm trial was set-up at Te Hana to measure milk production responses in 2 groups of 16 cows which were maintained on a) ryegrass-based pastures which contained wild-type endophytes which produced ergovaline and lolitrem B [+Ev] or on b) ryegrass pastures that were either free of endophyte or contained a novel endophyte which did not produce ergovaline or lolitrem B [-Ev]. The trial ran from October 1997 til mid-April 1998 and milk production was recorded for each cow at each milking for 10 consecutive days per month culminating in a herd test. There was no difference in milk production in October and November, but a difference of 25% developed in December in favour of the -Ev group and substantial differences in production were maintained until the trial was terminated. Effects of ergovaline on cow performance are discussed in relation to environmental and behavioural factors.

The prevalence of Wobbly Possum disease in a bush/farmland environment - Thompson EG; McLeod BJ (Proceedings of the New Zealand Society of Animal Production, 1999)
The prevalence of Wobbly Possum disease was monitored in wild-caught possums captured at 16 different sites. All animals were assessed for clinical signs of Wobbly Possum Syndrome from the time of their capture. Any that displayed symptoms were euthanased immediately and submitted for post mortem examination to confirm disease status. Of the 887 possums screened, 39 (4.4%) were infected with the Wobbly Possum virus. These had been trapped at 10 of the 16 sites (prevalence 0% to 23.3%). There were no significant differences in the proportion of infected animals among sites. The interval from time of capture to diagnosis ranged from 7 to 21 days. The presence of Wobbly Possum infection was not related to geographical location, sex of the animal or liveweight at the time of capture. This study suggests that both the natural prevalence of Wobbly Possum Syndrome, and the rates of cross-infection within a site are low.

The relationship between beef ultimate pH, breed of cattle, muscle glycogen and enzyme levels and animal behaviour - Webby RW; Fisher AD; Lambert MG; Turner P (Proceedings of the New Zealand Society of Animal Production, 1999)
To determine the incidence of high ultimate pH (pHu) across farms 967 cattle were involved in a survey which showed 3% of Angus, 21% of Simmental cross and 60% of the Friesians steers had an pHu above the acceptable maximum of 5.8. In further work, muscle (longissimus dorsi) biopsies samples were taken from 60 two-year-old Angus, Simmental cross and Friesian steers (n = 20 per breed) in late November and assayed for glycogen concentration and enzyme concentrations that indicated muscle fibre type. Behaviour measurements were made on all animals before slaughter. Individual measurements of carcass characteristics were made 22-24 hours after slaughter, including carcass weight, pHu, meat colour score, and fat depth (GR). Only one carcass had a pHu above 5.8 and there was no pHu difference between breeds (5.53, 5.55, and 5.58 for Angus, Simmental cross, and Friesian, respectively). There was no difference between breeds in the glycogen concentration in the muscle, although there were differences in enzyme concentrations that suggested differences between breeds in the proportion of the three muscle fibre types. Flight distance were small (4-7 m) but longer for Friesian than Simmental cross steers. There were no relationships between meat pHu and flight distance, glycogen concentration or muscle enzyme concentrations. Breed did not appear to effect pHu or muscle glycogen concentration.

Relationship between wool sulphur concentration and wool characteristics - Kenyon PR; Sherlock RG; Lee J; Blair HT (Proceedings of the New Zealand Society of Animal Production, 1999)
It is well established that naturally occurring wool sulphur concentration is lower in high wool-producing sheep, however little is known of the relationship between wool sulphur concentration and wool fibre characteristics. Mid-side wool samples were collected from ewe hoggets differing in lamb wool sulphur concentration. Wool from hoggets, which had lower wool sulphur concentrations as lambs, had longer staple lengths, were higher yielding and had lower loose wool bulk values. There was no relationship between wool sulphur concentration and mean fibre diameter or colour. An increase in length should have a positive effect on the price of wool, especially for second shear crossbred wools. At present the price premium for bulk is poorly defined, but is unlikely to have a significant impact on the value of these wools. These findings suggest that selecting animals for low lamb wool sulphur concentration will, if anything, positively affect the per kilo price of wool produced.

The relationship of meat quality to age at slaughter and indicators of animal age in red deer stags and hinds - Stevenson-Barry JM; Drew KR; Duncan SJ; Littlejohn RP (Proceedings of the New Zealand Society of Animal Production, 1999)
Groups of five stags and hinds were slaughtered in late summer (February/March) to examine the effects of age and sex of animal on meat quality. For both sexes the groups were the following ages: 1, 2, 3 and 5 years. In the 2 year old age group for stags there were three weight groups and additionally there was one group of 8 year old stags and one of 13 year old hinds. The group mean hot carcass weight (HCW) range was 51 to 119 kg for stags and 43 to 57 kg for hinds. The HCW`s tended to increase with age but the `light` and `medium` weight 2 year old males had lower (P< 0.05) mean HCW than all of the other male groups including the 1 year olds. The GR increase with age was much greater in stags than in hinds; 80% of the stags 3 years and older and 27% of the hinds 3 years and older graded over-fat. In both hinds and stags, GR was strongly related to carcass weight. Meat from 5 and 8 year old stags was much tougher (P< 0.05) than that from all other groups. Of all the attributes measured as possible indicators of animal age, only carcass neck a* value (redness) was able to accurately discriminate ages of animal and provided the best categorisation of animals into tenderness classes.

Relationships of fleece and fibre traits with unscourable yellow discolouration in a survey of strong wool sheep flocks - Bray AR; Smith MC (Proceedings of the New Zealand Society of Animal Production, 1999)
Wool samples were collected over two years from sixty two lines of sheep in flocks spread around New Zealand, to provide wool from a variety of strong wool genotypes and farming environments. Within-line relationships of unscourable discolouration with objective measured and subjectively assessed fleece and fibre traits were determined by correlation and regression analyses. The trait most highly correlated with the CIE measurement of yellow discolouration (Y-Z) within lines was Z (R2 = 0.58). CIE and Y values were more weakly correlated (R2 = 0.19 and 0.18, respectively) as was the maximum visibly assessed yellow score, and staple definition accounted for 33% of the variation. Variation in other fleece and fibre traits within flocks was associated with Y-Z. The reasons why the scoured wool of some sheep in a flock show more discolouration than that of others were not found among the 38 traits examined in this project.

The Relevance of Applied Bio-Physical Research: A Case Study into Beef Breeding Cow Twinning Technology - Parminter T; Smeaton D (Proceedings of the New Zealand Society of Animal Production, 1999)
Science funders need to know that their investment in technology will be relevant and useful. Pre-trial social research and the involvement of potential users in project management, enables scientists to ensure that these conditions are addressed. This paper examines the development of twinning technology for beef breeding cows as an example. Preliminary social research in 1995 showed that users wanted information about the technology and its interactions with sheep production and lamb finishing. They also wanted to know the labour requirements, and new skills needed for producing successful results. A systems trial examining these issues commenced at Whatawhata Research Centre later that year. A mentor group was initiated at the start of the trial with farmers, scientists, funders, and a vet included. This group was involved in trial management over the three-year period of the trial. The trial has shown that it may be profitable for farmers to produce twin calves and grow them out to 18 months of age or older, providing that they can manage calving. Twinning cows were shown to be complimentary to sheep breeding and lamb finishing. The role of the mentor group was evaluated in a survey of group members in 1997. The group was shown to be of high value to the individuals involved, and to the livestock industry, through providing greater opportunities for farmers and scientists to learn from each other. However, there was some concern that the mentor group process could increase the costs of carrying out research.

The results and success factors of nine group farm monitoring programmes - Sheath GW; Webby RW; Keeling P; Thomson RD; Page CR; Burton GT (Proceedings of the New Zealand Society of Animal Production, 1999)
Results from 9 farmer groups located in the upper North Island and operating over the period of 1988 to 1998 showed that group farm monitoring has facilitated changes in farm practice performance and income. The process in-volved groups of farmers with associated consultants, veterinarians and scientists; and the detailed monitoring of a central farm for 3 to 4 years. Changes made on the monitor farm incorporated the optimisation of the farm system and the adaptation and use of new sheep and beef cattle farming technologies. Increases in production ranged from 8 to 37%; and increases in farm revenue from 13 to 31%. Changes to stock policies that better aligned feed demand and supply, in-creased growth rates of young animals and greater efficiencies in breeding ewe and cow performance were common contributors to improved performances. The group farm monitoring process emphasised the value of gathering and effectively using farm and product information and provided a collective learning environment for farmers within a group context. Critical success factors that have emerged from a decade of work experience associated with group process are highlighted and discussed in the paper.

A review of forage grazing systems to produce venison according to market signals - Barry TN; Wilson PR; Kemp PD (Proceedings of the New Zealand Society of Animal Production, 1999)
Grazing systems are described for producing venison carcasses weighing 50-65 kg (92-120 kg liveweight) in the spring by one ear of age (30 November), using red and hybrid (0.25 elk: 0.75 red) deer stags. Grazing perennial ryegrass/white clover pasture at 10cm surface height during autumn, winter and spring resulted in 73% of young stags attaining the desired slaughter target, but variation between years was large (range 25-100%), with a contributing cause being variation between years in winter growth rate. When red clover and chicory were grazed during autumn and spring, with pasture grazing during winter, the proportion of young stags attaining the desired slaughter target was consistently increased to 90-100% and mean carcass weights were increased by 11 & 17% respectively. Largest responses in deer growth to red clover (26%) and chicory (47%) over perennial ryegrass - based pastures were seen during autumn. Both voluntary feed intake (VFI) and digestibility of the diet selected were higher for deer grazing chicory and red clover than perennial ryegrass-based pasture, with the largest effects seen during summer and autumn, when perennial ryegrass was of lowest nutritive value. In indoor studies, both the rates of ruminal degradation and outflow of chicory were greater than for perennial ryegrass, with similar results found for red clover. It was concluded that the faster breakdown and clearance of red clover and chicory from the rumen than perennial ryegrass explained their higher digestibility and VFI by grazing deer. Management of red clover and chicory to increase persistence on commercial deer farms and grazing systems to support year round supply of venison in a branded market strategy are also discussed. For successful venison production by 12 months of age, target growth rates during winter of 100g/day for red deer and 150g/day for hybrids are suggested.

A review of recent findings on myostatin - a gene which controls muscle growth - Bass J; Oldham J; Sharma M; Kambadur R (Proceedings of the New Zealand Society of Animal Production, 1999)
The enlarged muscles of certain breeds of cattle, such as the Belgian Blue, result from a marked increase in the number of normal sized muscle fibres. Originally insulin-like growth factors (IGFs) were implicated in this myofibre hyperplasia. Recently it has been reported that mice lacking a myostatin gene, a member of the TGFb super family, have enhanced skeletal muscle mass resulting from increased muscle fibre number and size. Mutations in this gene have been found in double muscled cattle, indicating that myostatin is an inhibitor of muscle growth. Myostatin is expressed early in gestation and then maintained to adulthood in certain muscles. Myostatin expression in bovine muscle is highest during gestation when muscle fibres are forming and some of the myogenic regulatory factors have elevated expression over the same period as myostatin. Myostatin and MyoD, myogenic regulatory factors expressed in muscle have been shown to differ between normal and hypertrophied muscle cattle breeds. This evidence strongly suggests that lack of functional myostatin is associated with an increase in fibre number which then results in a marked increase in potential muscle mass in double muscled cattle.

Sealing of the bovine teat canal after dry-off. - Lacy-Hulbert SJ; Williamson JH; Day AM; Woolford MW (Proceedings of the New Zealand Society of Animal Production, 1999)
Closed teats have proven more resistant to dry period mastitis than open teats. Natural rate of keratin plug formation within closed and open teats, and consequences of bacterial colonisation of the teat canal, were examined using 67 low somatic cell count cows. Cows were dried off without antibiotic therapy and teats assessed for closure status at 5, 10, 15 and 20 d after drying off. Weight and bacteriological status of the keratin plug was determined by reaming teats with a sterile pre-weighed tapestry needle 7 d prior to drying off and on one occasion post drying off. Initially (d 5), keratin weight for all teats increased by 100% compared to lactating teats (4.89 mg/qtr). Between d 10-20, keratin weight from open teats (29% of teats) was 34-55% less than for closed teats. Subclinical infections in the teat canal significantly reduced likelihood of teats closing after drying off.

Seasonal changes in the protein content and composition of ram seminal plasma - Smith JF; Parr J; Murray GR; McDonald RM; Lee RS-F (Proceedings of the New Zealand Society of Animal Production, 1999)
Seasonal changes in ram semen composition are accompanied by changes in fertility of frozen semen. These changes in fertility are not all easily explained simply in terms of the changes seen in sperm numbers per ejaculate. The possibility that changes in the composition of seminal plasma may be involved in the seasonal changes in ram fertility needs to be considered. An experiment that examined the protein content and composition of seminal plasma was conducted. Semen samples were collected from 10 rams ( 5 each from the BV -ve and BV +ve selection lines for early lambing) and the seminal plasma separated by centrifugation. Samples were collected with AV in the first week of each month for 12 months (after a 4-day period of abstinence). The protein concentration was determined and the samples were subjected to electrophoresis by SDS-PAGE using mini gels. Seminal plasma samples from all rams for each month were analysed on the same gel for each of the 12 months. In addition samples for all 12 months for each ram were also analysed on the same gel. The seasonal changes in seminal plasma protein profiles were recorded. There was a seasonal change in the total protein concentration of seminal plasma with higher levels (36.9 vs 23.0 mg/ml, P<0.001) observed during the breeding season (January to June). In the rams selected for out-of -season breeding (BV-ve) protein levels were also elevated in December and again in June and July. Several protein bands that were present in seminal plasma from all rams during the breeding season were absent from a number of rams during the non-breeding season (August to December). Their absence was confirmed on larger format 1D SDS-PAGE gels. The majority of these proteins fell between 20 and 70 kDa molecular weight. The absence of these proteins from seminal plasma coincides with the time of the year when we observed poor maintenance of motility in fresh semen and a reduction in the velocity of frozen/thawed sperm from semen collected from the same rams. Further work is required to identify and characterise these proteins and to elucidate their function and role in ram fertility.

Seasonal wool growth patterns and the follicle and fibre characteristics of New Zealand feral sheep - Pearson AJ; Ashby MG; Sumner RMW; Nixon AJ (Proceedings of the New Zealand Society of Animal Production, 1999)
Wool follicle and fibre characteristics, and aspects of their seasonality were assessed in feral sheep from the Hokonui Hills (Merino origin), Campbell Island (Merino x long-wool breeds) and Raglan Peninsula (Romney). Live weight, fleece weight, staple length, crimp frequency, fibre diameter, fibre curvature, follicle density and secondary to primary follicle ratio differed between breeds, reflecting their breed origins. Mean clean fleece weights of the feral breed groups were approximately half that of their modern counterparts. Factors contributing to the low productivity were reduced staple length and follicle density, and a brief cessation of growth by some follicles during spring. The mean amplitude of rhythms in seasonal wool growth and fibre diameter increased with age, and appear to have converged to similar values, contrasting with their modern breed counterparts.

Separate grazing as a breeding management strategy for anoestrous cows - Clark BA; Rhodes FM; McDougall S (Proceedings of the New Zealand Society of Animal Production, 1999)
The aim of this study was to compare the rate of resumption of oestrous cycles and fertility to first insemination between anoestrous cows grazed separately (Split) or grazed in the main herd (Control) for 28 days and untreated or treated with progesterone (CIDR) and ODB from 7 days before the planned start of mating. Oestrus was detected in 54.7%, 46.3%, 93.5% and 86.8% of cows (Control, Split, CIDR and Split+CIDR, respectively) by 28 days after start of treatment (P<0.05). Compared to controls conception to first insemination was no different in Split and CIDR groups, but was reduced in the Split+CIDR group (P<0.05). The percentage of cows pregnant by 28 days after examination was 26.4%, 18.9%, 42.1% and 31.4% for Control, Split, CIDR and Split+CIDR groups, respectively (P<0.05). There was no overall effect of separate grazing on milksolids production or cow liveweights, but milksolids did vary between herds (P<0.001). Separate grazing did not enhance the reproductive performance of anoestrous cows.

Sex and age effects on genetic parameters for wool production and qualities - Clarke JN; Dobbie JL; Jones KR; Wrigglesworth AL; Hickey SM (Proceedings of the New Zealand Society of Animal Production, 1999)
Heritabilities and genetic correlations were estimated for New Zealand Romney sheep from within the selected and control lines of a 25-year selection experiment for greasy hogget fleece weight and yearling body weight. Average repeatability of clean fleece weight in 1 to 5 year-old ewes was 0.56, 25% higher than the average heritability of 0.44. The average genetic correlation among measurements at different ages was 0.89. Sexual dichotomy in the relative predictive power of hogget records was most apparent for greasy and clean fleece weights but was evident to some degree for bulk and brightness as well, due mainly to lower heritabilities in male compared to female hoggets. Average co-heritability of greasy hogget with adult clean fleece weights was 25% lower for male (0.26) compared to female (0.35) hoggets, in this case due to a lower genetic correlation (0.69 vs 0.81) as well as a lower heritability (0.33 vs 0.43, respectively). A repeatability model seemed an adequate approximation for estimation of breeding merit for most wool quality traits studied but not for lifetime wool production.

Source of excess nitrogen may affect nutrient partitioning in lactating ewes - Malik B; Nicol AM; Van Houtert M (Proceedings of the New Zealand Society of Animal Production, 1999)
This experiment tested the hypothesis that the form of surplus nitrogen (ammonia or amino acids) affects nutrient partitioning in lactating ruminants. Nine, abomasally-cannulated, 4 year old Coopworth ewes (66.4 ± 5.9 kg liveweight), suckling twin lambs were offered a basal diet designed to meet their requirements for ME and MP in 12 equal portions at 2 h intervals for two periods of five weeks. During both periods, ewes were allocated to one of three groups; continuous abomasal infusion of 2 l water/day (control), infusion of 150 g sodium caseinate (20g N) dissolved in 2 l water or 85 g ammonium bicarbonate (15 g N) in 2 l water. Liveweight change of ewes and lambs, ewe milk production and composition and nitrogen balances were measured. Treatments had no significant effect on ewe dry matter intake, in vivo dry matter digestibility or ewe liveweight change. Rela-tive to control, casein infusion increased milk production (33%) and lamb liveweight gain (by 26% from 132 to 166 g/day) but had no effect on milk composition. In contrast ammonia infusion decreased milk production (15%), reduced milk protein concentration (from 63 to 56 g/kg), increased milk fat concentration (from 66 to 75 g/kg) and reduced lamb liveweight gain (from 132 to 66 g/day). The N apparently utilised (dietary N + infusate N faecal N urine N) was apportioned (milk N : body N) in ratios of 0.86 : 0.14, 1.0 : 0 and 0.52 : 0.48 for control, casein and ammonia infusions respectively. It is concluded that excess N in the form of ammonia diverted protein from milk production to body retention, thus the form of surplus N may affect nutrient partitioning in lactating ewes.

Suitability of serum oestrone sulphate measurement to verify pregnancy in red deer - Henderson KM; Beatson N (Proceedings of the New Zealand Society of Animal Production, 1999)
The mean ± s.e.m. concentration of oestrone sulphate (OS) in serum from 31 non-pregnant red deer was 2.0±0.2 ng/ml. The value 3 standard deviations above this mean was 6.2 ng/ml which represents the highest serum OS concentration likely to be found in non-pregnant deer. Only 2 out of 40 serum samples obtained from 15 deer between 118 and 182 days pregnant had an OS concentration >6.2 ng/ml, the overall mean ± s.e.m. value for the 40 samples being 2.4±0.3 ng/ml. On days 195 and 209 of gestation, 5 of 10 deer and 7 of 9 deer respectively had serum OS concentrations above 6.2 ng/ml; the mean ± s.e.m. concentrations on days 195 and 209 being 7.2±1.3 ng/ml and 14.9±3.4 ng/ml respectively. These results show that mean serum OS concentrations rise markedly in red deer during late gestation, and that by day 209 serum OS concentrations have risen above 6.2 ng/ml in most hinds. Measuring serum OS concentrations in the last month before expected calving may offer an alternative to ultrasonography for verifying pregnancy status in red deer.

Synchrony of onset and cessation of breeding activity in brushtail possums (Trichosurus vulpecula) in coastal Otago, New Zealand - McLeod BJ; Thompson EG; Crawford JL (Proceedings of the New Zealand Society of Animal Production, 1999)
The onset of breeding was monitored in 117 female brushtail possums trapped at a single location between December and May, with reproductive status being determined at the time of capture. The cessation of breeding activity was monitored in captive animals in which reproductive status was determined in October (N=38), November (N=39) and January (N=30), by laparoscopic observation of their reproductive tracts. Comparison was made between animals that had pouch young removed (RPY) 7-9 days previously, and possums that had not had pouch young present for at least 40 days. Only 1/57 possums trapped over the period from 1 December to 31 March had recently bred. In contrast, 49/60 (82%) possums captured between 1 April and 6 May, were either pregnant or had new-born pouch young. In spring (mid-October) 45% of possums continued to cycle, only 13% were cycling in late November and all were anoestrous in January. There were no relationships between liveweight or RPY and reproductive status.

Tactical supplementation of beef finishing cattle - Boom CJ; Sheath GW (Proceedings of the New Zealand Society of Animal Production, 1999)
The impact of high quality supplementary feeds on cattle growth rates was investigated in 2 experiments. The first experiment was conducted during late summer (8 weeks) and involved 5 treatments which were replicated twice: no supplement, 2 and 4 kg rolled maize grain/hd/d; and 2.3 and 4.6 kg DM/hd/d high quality pasture silage. The second experiment was conducted during late winter (8 weeks) and involved 3 treatments which were replicated twice: 0, 2 and 4 kg/hd/d rolled maize grain. Rising 2 year steers were used and all pre- and post-grazing pasture masses were similar between treatments within each experiment. During the summer experiment pasture quality was poor and steer liveweight gains for the 5 treatments were: -0.04, 0.44, 0.55, 0.29 and 0.36 kg/hd/d respectively. In contrast, pasture quality was high during the winter experiment and liveweight gains were: 0.93, 1.09 and 1.25 kg/hd/d respectively. The combined results of this experimental series show a consistent liveweight gain response to supplementation of high quality feeds, under both low and high quality pasture conditions. A general response of 0.15-0.20 kg liveweight gain/kg DM grain can be expected. Given current grain prices in New Zealand, its use as a tactical supplement in beef finishing systems will be confined to overcoming variable forage supply and attaining supply contract premiums. Pasture silage is an alternative supplement for summer, but high quality is a pre-requisite.

Toxicity effects of 1080 on pregnant ewes - O'Connor CE; Milne LM; Arthur DG; Ruscoe WA; Wickstrom M (Proceedings of the New Zealand Society of Animal Production, 1999)
There are no data on the potential for 1080 used for pest control to cause delayed deaths or impaired productivity in livestock following multiple, sub-lethal doses. Recent losses of late-gestation ewes exposed to weathered 1080 baits has also led to speculation that pregnant ewes may be unusually sensitive to the toxin. To address these data gaps, groups of 20 Perendale ewes, non-pregnant or pregnant with twins, were administered either a single (0.25 mg/kg) or multiple oral doses (0.05 mg/kg over 3 consecutive days) of a 1080 cereal pellet. The highest mortality occurred in the single dose groups (pregnant 45%, non-pregnant 21%) compared to the multiple dose groups (pregnant 35%, non-pregnant 0%). There was no mortality in the control group of pregnant ewes. Log-linear modelling showed highly significant treatment effects (P = 0.0003) and differences (P = 0.045) in acute mortality rates between pregnant (40%) and non-pregnant ewes (10%), which was linked to increased bioavailablity. There were no differences in the incidence of metabolic diseases, lambing percentages, lamb survival, or growth rates between dosed and undosed pregnant ewes. This study demonstrated that extra care should be taken to avoid exposure of pregnant ewes to even small bait fragments, but also provides further evidence that there are no long-term health effects in animals that survive accidental 1080 poisoning.

Ultrasonic pregnancy scanning - a tool for change - McCorkindale AB (Proceedings of the New Zealand Society of Animal Production, 1999)
The advent of ultrasonic pregnancy scanning has provided new opportunities for the management of breeding ewes. Major benefits of scanning are better allocation of feed resources and improved management at lambing, as well as being a tool to improve the genetic merit of flocks. Scanning results are also the catalyst for farmers focusing more clearly on their flocks` relative reproductive performances either informally through comparing scanning percentages and fertility indices with neighbours, or formally through comprehensive farm monitoring reports.

Use of ultrasonic pregnancy scanning information for farmer extension - Geenty KG (Proceedings of the New Zealand Society of Animal Production, 1999)
Ultrasonic pregnancy scanning is a new technology that provides sheep farmers with information that can significantly improve flock performance. The effective use of this information requires participation from the scanner operators, consultants, scientists, veterinarians and company representatives. Farmer networks such as the Sheep Council and monitor farms also have an important role in maximising the benefits to individual farmers by sharing knowledge and experience on the management changes made possible by pregnancy diagnosis.

Validation of body condition scoring by using ultrasound measurements of subcutaneous fat. - MacDonald KA; Verkerk GA; Penno JW (Proceedings of the New Zealand Society of Animal Production, 1999)
Visual assessment of body condition score (BCS) is used to aid individual cow and herd management, but the assessment is subjective and does not estimate actual body tissue reserves. Ultrasound (US) measurements of external fat reserves may be more objective. To quantify fat reserves at differing BCS`s, fat depth was measured by US on 87 mixed aged Friesian dairy cows on 6 occasions during a year. The US measurements were made at the 12th rib (RIB) and mid-way between the hip and pin bones (HIP). Animals were weighed (LW) and their BCS assessed visually at the same time. Mean BCS was greatest in early summer at 4.5 and lowest in late summer at 3.6. Mean RIB varied from 2.2 mm in mid spring to 3.6 mm in early winter, while mean HIP varied from 1.6 mm in early summer to 4.2 mm in early winter. Changes in BCS and LW were positively correlated. Age and growth in 2 year old animals did not appear to affect this relationship. BCS was positively correlated to both RIB and HIP fat depth. The correlation coefficient varied with time, being smallest in late summer (r = 0.37 & 0.26 for RIB & HIP respectively) and greatest in late lactation (r = 0.69 & 0.82 for RIB & HIP respectively). The ability of RIB & HIP measurements to predict BCS was low when BCS was <4.5, but predictability increased as fat depth and body condition increased. Cows at lower scores may deposit or deplete fat internally while having few external fat deposits. Because large changes in liveweight (LW) occurred without changes in BCS, or US, it is possible that fat deposits are internal or intramuscular rather than subcutaneous, and therefore not detectable from external inspection. Since most BCS values are <4.5 for lactating cows, the value of ultrasound to assess fat depots in lactating dairy cows is limited; however it may be of some value with cows of BCS >4.5.

Variation in lamb survival within farm and between farms - Tarbotton IS; Webby RW (Proceedings of the New Zealand Society of Animal Production, 1999)
Variation in lamb loses between scanning and docking were investigated in 1997 in a survey and an on farm study. Ultrasonography results on MA ewes showed a range from 130 to 191% foetuses scanned/ewes present. Ewe weights at joining ranged from 54 to 70 kg. Survival of multiple and single was 78%, and 92% respectively. Differences between scanning and docking comprised 21% ewe deaths, 49% dead lambs and 30% missing /unseen. Paddock docking results were 157% to 188% for ewes with 2 lambs and from 90% to 109% for 1 lamb. Paddocks were assessed on the basis of slope, aspect, shelter, hazards and disturbance. Lack of shelter on easy contours, disturbance and steep slopes appeared to exacerbate lamb deaths. Adverse weather was not a factor in the year of this study.

Vital components of industry-wide benchmarking - Rohloff RM (Proceedings of the New Zealand Society of Animal Production, 1999)
For the full benefits to be realised from farm monitoring and benchmarking it is essential that it is available to all farmers at an affordable price. The data must be relevant to participants, easily collected, and processed into a form that is easily understood. NZFT2000 is an example of how these principles can be put into practice for the benefit of individual sheep farmers and the whole sheep industry.

Amylin causes hypocalcaemia in lactating goats - Brief Communication - Min SH; Farr VC; Lee J; Cooper GJS; Davis SR (Proceedings of the New Zealand Society of Animal Production, 1998)
Amylin is a 37-amino acid peptide, structurally related to calcitonin-gene-related peptide (CGRP), adrenomedullin and calcitonin (CT). It is co-secreted with insulin from the pancreatic ß-cell. There is increasing evidence from rodent models that amylin may play an important role in the regulation of mineral metabolism, particularly Ca (Cooper, 1997). However, such a role has never been investigated in a ruminant model. The aim of this study was, therefore, to investigate a role for amylin in the regulation of Ca and metabolism of other minerals in lactating goats.

Arterio-venous differences of amino acids across the mammary gland of cows fed fresh pasture at two levels of dry matter intake - Pacheco-Rios D; McNabb WC; Cridland S; Barry TN; Lee J (Proceedings of the New Zealand Society of Animal Production, 1998)
Four cows housed indoors in metabolism stalls were used in a cross-over experiment to test the effect of two levels of dry matter intake on amino acid metabolism during early lactation (October). Fresh ryegrass/white clover pasture was offered ad libitum or at 75% of the ad libitum intake during 2 experimental periods. Concentrations of essential amino acids (EAA) in arterial and mammary venous plasma were determined as indicators of the uptake and utilisation of individual AA for milk protein synthesis in the mammary gland. The relative concentrations of free EAA (expressed as % of total EAA) of lysine, tyrosine, leucine, phenylalanine, methionine, tryptophan and histidine were lower in arterial plasma than those in the milk protein, suggesting these as limiting EAA. Using extraction rates of plasma as an indicator of potentially limiting amino acids, leucine, lysine and methionine appeared, in that order, as the most limiting amino acids in the ad libitum animals. In the intake restricted animals, the order of limitation appeared to change to methionine, lysine and leucine.

The assessment of natural means of controlling loose wool feltability and yarn shrinkage. - Kenyon PR; Wickham GA; Blair HT (Proceedings of the New Zealand Society of Animal Production, 1998)
Midside wool samples from Romney and ¾ Romney ¼ Merino cross (¼M) hoggets were tested for loose wool feltability. Romney samples were also hand spun and yarn shrinkage measured. Sire progeny groups accounted for 6.5% of the variation among samples in loose wool felting (P<0.10) and 12% in yarn shrinkage (P<0.05). Fibre traits most highly correlated with feltball diameter were loose wool bulk (r = 0.65 for Romneys and 0.73 for ¼M), crimp frequency (r= 0.53 and 0.41 respectively) and lustre (-0.30 and -0.40 respectively). Loose wool bulk (r= -0.25) and greasy fleece weight (r=-0.40) were most correlated to yarn shrinkage. These results suggest that low-shrinkage wools could be produced by selecting rams on shrinkage of yarn. Loose wool feltability might also be changed by direct or indirect selection.

Balancing pasture and maize silage diets for dairy cows using urea, soybean meal or fishmeal - MacDonald KA; Penno JW; Kolver ES; Carter WAC; Lancaster JAS (Proceedings of the New Zealand Society of Animal Production, 1998)
Four treatment groups of 10 Holstein-Friesian cows were established at the DRC No. 2 dairy in the spring, summer and autumn of 1996/97 to test the efficacy of providing urea, soybean meal or fishmeal supplement to overcome the protein deficiency that occurs when cows are supplemented with large amounts of maize silage. Pasture allowance was manipulated to achieve an average pasture dry matter (DM) intake of 6.6kg/cow/day for each group. Treatment groups were supplemented with 75 MJ ME/cow/day as either 7.0kg DM of maize silage, 7.0kg DM of maize silage plus 90g of urea, 5.2kg DM of maize silage plus 1.4kg DM of soybean meal, or 5.8kg DM of maize silage plus 1.0kg DM of fish meal. The addition of urea as a source of non-protein nitrogen had no effect on milk, milkfat or milk protein production. Soybean meal increased milk protein production by 0.06kg/cow/day in both summer and autumn (P<0.01). Fishmeal increased milkfat production by 0.07 (P<0.01) and 0.08kg/cow/day (P<0.05) in summer and autumn and increased milk protein by 0.06 (P<0.01), 0.10 (P<0.01) and 0.08kg/cow/day (P<0.001) in spring, summer and autumn, respectively.

Calpain and calpastatin activity in muscle from genetic lines of lambs selected for divergent levels of fatness. - Morton JD; Bickerstaffe R; Purchas RW (Proceedings of the New Zealand Society of Animal Production, 1998)
There is widespread interest in the extent to which genetic factors influence meat quality. In this study we examined meat quality characteristics and the activity of the calpain protease system in M. longissimus lumborum (LL) from backfat selection lines of Southdown lambs. The high fat line produced heavier carcasses with greater soft tissue depth GR. LL from the high fat line animals had a lower ultimate pH and was significantly more tender at 24h post-mortem using the MIRINZ tenderometer but not the Warner-Bratzler peak force. There was a decline in m-calpain and calpastatin activity but not m-calpain in the 9h post-mortem. There were no significant differences in the levels of the calpains or their inhibitor between high and low backfat lines. However, when the results were adjusted for pH, the 20 min calpastatin levels were highest for the sire group that had the highest peak force value.

Calpain and tenderness comparisons in M. longissimus dorsi samples from weight-selected and control Angus cattle - Morris CA; Speck PA; Cullen NG; Dobbie PM (Proceedings of the New Zealand Society of Animal Production, 1998)
Meat samples (M. longissimus dorsi) from a control Angus herd (ACO) and associated selection herd (AS1) were compared for calpain/calpastatin concentrations and shear-force tenderness, after the herds had been subjected to 22 to 24 years of random replacement or selection for increased adjusted yearling weight. The objective was to monitor changes in meat tenderness at fixed slaughter date resulting from genetic selection, and associated changes in muscle calpain or calpastatin concentrations. Bull calves (n=94), from 3 successive calf crops raised on pasture, were slaughtered immediately after arrival at the abattoir at about 20 months of age on one day each year (May 1995, 1996 and 1997). Carcasses were electrically stimulated, weighed and hot boned. Meat samples for calpain/calpastatin analysis were taken within 30 minutes of slaughter from the M. longissimus dorsi, with further samples after 24 hr of ageing at 10°C. Shear-force tenderness was assessed on the same muscle at intervals from 24 hr until one month of ageing at -1°C. Calpastatin, milli- and micro-calpain activities were assayed using casein as a substrate. Yearling live weights, hot carcass weights and muscle weights were respectively 19.0%, 16.5% and 17.3% greater in the AS1 than the ACO herd (all P<0.001). The AS1 samples were on average 8 to 16% more tender than ACO samples (P<0.05) on days 1 and 3 post mortem, but there were no significant herd differences in tenderness at later ageing times. The between-animal repeatability of shear-force tenderness from days 1 to 28 was 0.44±0.07. Millicalpain concentrations were significantly lower in the AS1 than ACO samples by an average of 13% (P<0.001), and there were smaller differences in microcalpain and calpastatin between herds in the same direction. These results show that early post mortem tenderness, millicalpain and possibly microcalpain and calpastatin concentrations were associated with genetic differences in growth.

Is carcass classification useful or necessary? - Kirton AH (Proceedings of the New Zealand Society of Animal Production, 1998)
The need for a N.Z. Meat Producers Board (NZMPB) supervised classification system for export carcasses has been widely debated by the farming community and elsewhere while the Producers Board Acts Reform Act (1997) has been discussed through parliament. Supervision of the export carcass classification is one of the remaining NZMPB (recently renamed Meat New Zealand) functions with the classification being undertaken by company graders. As meat companies select the carcasses most suited to provide the meat/cuts for particular meat export orders, they argue that a national carcass classification system is unnecessary. Today most carcasses are sold as cuts rather than as entire carcasses. Carcass exports provided the main reason for the initial development of a national classification system to facilitate trading overseas `sight unseen`. However carcass grading/classification also provides a common language of communication which, when associated with a payment system, allows producers to compare prices from different exporters and provides market signals as to the type of carcass most required. Export carcass classification indicates composition and yield of saleable meat. NZMPB supervising graders are seen as giving a independent check on company graders, a feature disliked by some processors but endorsed by most producers. A uniform national system as is current in New Zealand also provides good data on which to base any future production plans. If based on objective measurements, a national classification system could also be run concurrently with any company system with a computer printing out the results of both systems. It is important that producers receive back factual information on the carcasses they are growing with information on how well they fit market requirements. The recent passage of the Producer Board Acts Reform Act (1997) has noted that the compulsory carcass classification for beef is to be reviewed or phased out in one year and sheep classification system is to be reviewed in two years. Unless the Meat Industry Association agrees with their retention, they will be phased out. If this happens, it may place too much power in the hands of the industry player currently having access to most of the market information and farmers will have no way of comparing between processors.

Cost-benefit analysis of commercial use of the Inverdale prolificacy gene - Amer PR; McEwan JC; Dodds KG; Davis GH (Proceedings of the New Zealand Society of Animal Production, 1998)
The Inverdale prolificacy gene is one of several potential major genes currently being explored for commercial application to the New Zealand sheep industry. We calculated economic benefits of two strategies to breed Inverdale carrier stud rams using gene flow methodology. Strategy 1 involves continuous transition matings from a conventional stud flock to generate Inverdale carrier ewes while Inverdale carrier ewes are self replacing in Strategy 2. Strategy 1 involved less DNA testing per ram sold, resulting in a $140 saving in testing costs at $50 per test. Reduction in conventional genetic response was also lower for Strategy 1 (<5% as opposed to 24% for Strategy 2) although Strategy 1 requires closer monitoring of animal identification and some Inverdale rams must be kept to produce carrier ewes. Commercial Inverdale use was shown to be highly beneficial in an existing terminal sire mating system with an added value over a normal ram of $3350 per Inverdale ram purchased. This was also highly cost effective with an expected DNA test price of $50 to $75 per sheep genotyped.

Current status of a candidate gene marker for bloat susceptibility in cattle - Wheeler TT; Haigh BJ; Wilkins RJ; McCracken JY; Morris CA (Proceedings of the New Zealand Society of Animal Production, 1998)
Pasture bloat costs New Zealand`s dairy industry at least $25M annually. We have previously shown that a salivary protein is increased in abundance in saliva from cattle that have been selected for low susceptibility to bloat compared with those selected for high susceptibility. We have now obtained the cDNA sequence for two closely related forms of this protein, which we term bSP30a and bSP30b. These share 83% sequence identity at the amino acid level, but at best only 28-30% homology with salivary proteins from other species. Analysis of genomic DNA by PCR suggests that the two forms of bSP30 are coded on two separate genes. However, the function of bSP30 and how it might influence susceptibility to bloat remains as yet unknown.

The determination of sulphur in wool using near infrared reflectance spectrometry - Corson DC; Martin W; Lee J (Proceedings of the New Zealand Society of Animal Production, 1998)
A method and calibration for estimating sulphur (S) concentration in wool using near infrared reflectance spectrometry (NIRS) is described. The NIRS measurements were calibrated against wet chemistry determinations of wool S (R² = 0.81, relative standard error ± 3.7%, n=339). The first derivative spectra with 14 partial least squares terms gave the lowest cross-validation error for the calibration using an independent set of wool samples (R² = 0.78, cross-validation error ± 0.11, n=66, mean 2.88 g S/100g wool). The correlation spectrum gave a series of approximately equally weighted peaks from about 1300 - 2400 nm, corresponding to -NH stretching and bending modes (protein). The -SH absorption between 1736 and 1746 nm could also be identified. Although scouring differences contributed to marked spectral differences in the visible region (yellowness was related to the first 3 principal component scores) these did not affect the overall S calibration. Uses for the calibration include wool S as an indicator of lifetime wool production, changes in wool composition in response to supplemented cysteine or energy intake, and the relationship between wool S and wool characteristics.

Development of an experimental herd for investigating maternal contributions to fertility in recipient cattle - McMillan WH; Donnison MJ; Cox SF (Proceedings of the New Zealand Society of Animal Production, 1998)
In order to develop an experimental resource to understand the biology of superior recipients, each of 155 contemporary yearling heifers received 2 in vitro-produced embryos on 6 occasions during a 30-month period. The number of foetuses present were determined at Day 60 of pregnancy, and pregnancies terminated. Heifers were ranked for their aggregate pregnancy performance, and the highest and lowest 25 were retained. Mean pregnancy rates of all recipients ranged from 0.20 - 0.67 depending on transfer occasion. The mean ± s.e. pregnancy rate of the High and Low groups were 0.77 ± 0.07 vs. 0.11 ± 0.06 respectively (P<0.001). No significant differences were observed between the two groups in oestrous cycle progesterone profiles or follicular dynamics. We conclude that repeated twin embryo transfer can be used to identify recipients of high and low potential fertility, and that uterine, rather than simple ovarian parameters, may be better correlates with high pregnancy rate.

Differential effects of short-term once-daily milking on milk yield, milk composition and concentrations of selected blood metabolites in cows with low or high pasture intake - Auldist MJ; Prosser CG (Proceedings of the New Zealand Society of Animal Production, 1998)
Forty-eight Friesian cows were subjected to ad libitum grazing (pasture allowance 45 kg/cow/day) or restricted grazing (pasture allowance 16-18 kg/cow/day) in a cross-over experiment during spring. Mean milk yields for ad libitum and restricted cows after 10 day treatment periods were 21.4 and 16.2 l/day respectively. All cows were then subjected to once-daily milking (ODM) for 2 days. ODM reduced milk yield and casein:whey protein ratios but increased concentrations of fat, serum albumin, immunoglobulin G, whey protein and somatic cells. Effects of ODM were greater in fully fed and thus higher-producing cows. In blood, ODM decreased concentrations of non-esterified fatty acids and urea, but increased concentrations of glucose. Milk yield and composition were significantly affected by short-term ODM, but the effect was less in cows producing below their peak due to feed restriction. There were metabolic indications that ODM reduced the nutritional demands of milk production.

Diurnal variation in concentration of Beta-lactoglobulin in bovine milk. - McLaren RD; Auldist MJ; Prosser CG (Proceedings of the New Zealand Society of Animal Production, 1998)
Two trials were conducted to define the variation in concentrations of b-lactoglobulin (b-LG) in bovine milk following different milking intervals. In the first, milk samples were collected from three herds of 20 cows. At the time of sampling in early summer, one herd was in each of early, mid and late lactation (30, 120 and 210 days post calving, respectively). Average b-LG concentrations were 41, 37 and 50% higher (p<0.05) after a 16h than 8h milking interval for early, mid and late lactation, respectively. In the second trial, bulk milk was sampled from four herds of 12 cows. All cows were at the same stage of lactation and the milking interval was 16:8h. Samples were collected on three separate occasions when cows were on unrestricted pasture intake and once when intake was restricted by 50%. On unrestricted pasture intake, concentrations of b-LG were 11% higher in milk collected after 16h than 8h milking interval, whilst on restricted intake, concentrations were 44% higher. There were no differences in concentrations of a-lactalbumin (a-LA). Both trials show a significant difference in b-LG levels in milk collected after 16h versus 8h milking interval, although only 71% of all samples collected in the first trial exhibited this difference and it was less in the second trial using bulk milk.

The Effect of Blood Sampling Site on Measures of Stress in Dairy Cattle - Brief Communication - Morrow-Tesch J; Whitehead K (Proceedings of the New Zealand Society of Animal Production, 1998)
Stress has a negative impact on livestock production. Several physiological indicators currently exist to identify when animals are experiencing stress. Recently it has been suggested that the site of blood sampling may influence clinical pathologic parameters in rodents (Nasir et al., 1996). Because of the difficulty interpreting multiple physi-ological measures of stress and their high variation within animals we conducted a study to 1) determine the effect of blood sampling site on physiological measures of stress in dairy cows and 2) identify new quantifiable indicators of stress.

The effect of calving season on milk production. A system study. - Garcia SC; Cayzer FJ; Holmes CW; MacDonald A (Proceedings of the New Zealand Society of Animal Production, 1998)
A 3-year trial is being conducted at No1 Dairy Farm, Massey University, to compare the effect of calving season on the whole system of production, and the results of the first year are presented here. Three different systems were implemented by stocking each farmlet (40 ha) with Friesian cows which calved either in Autumn (A), in Spring (S) or 50% in A and 50% in S (A/S). Average stocking rate (SR) was 2, 2.25 and 1.95 cows per ha, respectively. A larger area was conserved as silage in A than in A/S and S, which also affected pasture growth rate in Spring. More supplements (t DM/cow) were fed in A (1.2) than in A/S (0.8) or in S (0.4). The higher yield of milk solids (MS) per cow for cows which calved in Autumn compensated the lower stocking rates of those herds and resulted in similar levels of production per ha (705-725 kg MS) for all three systems. These first year results suggest that similar levels of production per ha can be achieved with different calving systems and they emphasise the importance of farm systems studies as a research tool.

The effect of dairy herd management and milking practices on milk quality. - Londono-Gutierrez P; Anderson WJ (Proceedings of the New Zealand Society of Animal Production, 1998)
A mail survey to 200 dairy company suppliers in July 1996 received a 46% response. Certain practices (e.g. SAMM (Seasonal Approach to Managing Mastitis) plan) reported by seasonal supply farmers were compared with their company’s milk quality records for the 1995/96 year. An indicator of udder health was Bulk Milk Somatic Cell Count (BSCC). Mean BSCC (1995/96 lactation) for survey respondents was 217,000 cells/mL. 35% achieved a seasonal average BSCC<150,000 cells/mL; 3% had BSCC>400,000 cells/mL. Milksolids per hectare was significantly (p<0.01) and negatively correlated with BSCC. "Low BSCC" suppliers (<120,000 cells/mL) reported using similar dairy husbandry and milking procedures to the 65% of suppliers with BSCC above 150,000 cells/mL. 45 % with BSCC<250,000 cells/mL consciously used the SAMM plan compared to 22% among those with BSCC>250,000 (p<0.05). Farm dairy hygiene, detection and treatment of mastitis infection (lactating or dry cow therapy), drying-off and culling of selected cows remain important practices for maintaining milk quality.

The effect of grazing management on pasture and animal production late Autumn to Early-Spring period in a one year Bull Beef Grazing System. - Coutinho HB; Matthews PNP; Morris ST (Proceedings of the New Zealand Society of Animal Production, 1998)
The aim of this trial was to improve pasture growth rate and animal liveweight gains in the late autumn and early spring on a one year bull beef production system. The trial was conducted at the Tuapaka bull unit, Massey University, from 1 April to 30 September 1997. It compared three contrasting managements, operating on a total of 165 bulls stocked at 2.6 bull/ha. Treatment 1 followed a grazing plan based on the average pasture growth rate for the region, the animal requirements needed to achieve performance targets, and pasture mass targets (2700-2800 kg DM/ha and 1500-1600 kg DM/ha for late autumn and early spring, and 3000-3200 kg DM/ha and 1100-1200 kg DM/ha for winter for pre-grazing and post-grazing, respectively). Treatment 2 was managed according to the same pre-grazing and post-grazing targets. In this treatment the pasture targets were monitored daily, and bulls were shifted when the post-grazing targets were achieved. No supplement was used in Treatments 1 and 2. Treatment 3 followed traditional Tuapaka management, based on a 50 day rotation over the late autumn and winter, a 30 day rotation in August, and set stocking in September. Supplement was fed to this treatment as required in the winter. The overall liveweight gain (0.84 ± 0.02, 0.87 ± 0.02, 0.74 ± 0.01 kg LW/head/day for Treatments 1, 2, and 3 respectively) and final liveweight (354.7 ± 3.54, 359.8 ± 3.65, and 335.6 ± 3.27) were similar for Treatments 1 and 2 which were both significantly higher (P<0.001) than Treatment 3. Net herbage accumulation was significantly different (P<0.01) between Treatment 1 (6147 ± 369.3 kg DM/ha), Treatment 2 (7062 ± 319.9 kg DM/ha), and Treatment 3 (5277 ± 334.08 kg DM/ha). It was concluded that it is possible to improve both pasture production and bull beef performance when grazing is based on the management of prescribed sward conditions.

Effect of luteolysis on control of ovarian follicles using oestradiol benzoate and progesterone in cattle - Burke CR; Morgan S; Clark BA; Rhodes FM (Proceedings of the New Zealand Society of Animal Production, 1998)
This study aimed to determine whether progesterone from intravaginal insertion of a CIDR device could substitute for luteal progesterone and facilitate oestradiol benzoate (ODB)-induced control of ovarian follicle waves in the event of luteolysis. Luteolysis was induced by an injection of prostaglandin-F2a on Day 13 of the oestrous cycle in 24 lactating dairy heifers. Concurrent treatments on Day 13 were: i) 1 mg ODB i.m. (ODB1); ii) CIDR for 6 days (CIDR); iii) 1 mg ODB i.m. plus CIDR for 6 days (ODB1/CIDR); or, iv) 2 mg ODB i.m. plus a CIDR for 6 days (ODB2/CIDR). Examination of the ovaries using ultrasonography showed that oestrous cycles comprising 2 follicle waves predominated among ODB1 and CIDR groups; whereas combination treatments produced mostly 3-wave cycles (p<0.05). Day of ovulation was 15.4 ± 0.3, 21.2 ± 0.2 and 22.5 ± 0.2 for ODB only, CIDR only and 1 or 2 mg ODB plus CIDR cows, respectively (p<0.01). The interval from day of emergence to ovulation of the ovulatory follicle was less (p<0.01) in cows treated with ODB only (6.0 ± 0.3 days), or ODB plus a CIDR (7.2 ± 0.6 days), compared to a longer interval in those receiving a CIDR only (11.0 ± 0.8 days). These results showed that progesterone from a CIDR device was able to facilitate ODB-induced follicle wave turnover at the time of luteolysis in lactating dairy heifers.

Effect of maternal nutrition during early and mid gestation on fetal growth - Cooper K; Morris ST; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1998)
Two studies were conducted to examine the effects of maternal nutrition during early and mid-gestation on fetal growth. In the first, crossbred heifers were managed for High (H, 0.6 kg/day) or Low (L, 0.1 kg/day) live weight gains from mating until day 140 of gestation. Treatments were then reversed so that effects of nutrition during early gestation were not confounded by differences in maternal live weight at calving. Maternal liveweights (kg, Mean±SE, n=30/group) were (L vs H) 350.6±4.9 vs 394.3±5.3 (P<0.001) at day 140 of gestation and 393.5±5.3 vs 394.4±5.8 (P>0.05) at term. Calf birth weights (L vs H) were 30.9±0.7 vs 29.9±0.8 kg (P>0.05). In the second study, 60 Romney ewes were allocated to three nutritional treatments, 0.5 maintenance (M), 1.0M or 1.5M from days 21 to 101 of gestation. At day 101, ewe liveweights were 45.8±1.4, 56.8±1.4 and 69.1±1.4 kg respectively (P<0.001). Fetal weights at slaughter (day 101 of gestation) were 1249.9±40.6, 1280.8±38.0 and 1379.8±35.2 g respectively (P<0.05). These results indicate that, although the fetus places a relatively small nutritional demand on the dam in early gestation, fetal development can in some situations be influenced by maternal nutrition, particularly when dams are over- rather than under-fed.

Effect of pasture supplemented with methionine on wool growth and selected growth parameters - Purchas BJ; Waghorn GC; Wickham GA (Proceedings of the New Zealand Society of Animal Production, 1998)
The effects of a supplemental oral drench of rumen-protected methionine (Mepron®) on wool growth and weight gain was studied in 2-3y non-mated Romney ewes during nine months from March to December. Three groups of 20 sheep received either 0, 4 or initially 8 (later 2) g of methionine daily. The ewes were rotationally grazed as a single mob on ryegrass-white clover pasture with winter restrictions. Pasture availability was monitored weekly. Mid-side wool samples were taken at two-monthly intervals and analysed for yield. Full fleece samples were collected during end of trial shearing and analysed for yield, fibre diameter, colour, staple length, crimp and style. Sheep were weighed weekly and herbage intakes estimated in August and November. Blood samples for plasma cysteine determinations were collected in June, August and November. There were no significant differences between the control and 4g/d groups in clean wool growth from mid-side patches (mean 1260 mg/cm²/d), greasy fleece weight (4.12kg) or final live-weights (63.1kg). Average estimates of pasture intake were non-significantly lower in supplemented sheep in August but approached significance in November (P<0.11). There were no treatment effects on wool growth rate or wool characteristics even though Mepron increased (P<0.05) plasma cysteine concentrations (umolar) (control 40.5 vs 4g/d 45.3) in June and in August (25.9 vs 31.1) but not in November. Weight-adjusted back-fats depths were lower in both supplemented groups compared to controls (P<0.05). We conclude that simple deficiencies in sulphur-containing amino acids were not limiting for wool production in these grazing sheep.

Effect of prior ram-ewe contact on the ability of rams to stimulate early oestrus - Knight TW; Ridland M; Litherland AJ (Proceedings of the New Zealand Society of Animal Production, 1998)
Ram-ewe contact when ewes are in anoestrus may reduce the ram`s ability to stimulate oestrous activity in ewes. Conversely, oestrus ewes increase the ram’s ability to stimulate ewes, possibly by increasing plasma testosterone concentration (T). On 25 November, 400 Romney ewes and 12 Dorset teasers were each randomised into 2 groups. One group of ewes and rams were joined while the others were isolated from the opposite sex. On 14 January (day 0) half of each group of ewes was joined for 35 days with either rams which had been previously exposed or not exposed to ewes, and mating marks were recorded each week. In a second experiment, 16 Romney rams were introduced (day 0) to oestrus or non-oestrus ewes and bled on days -1, 0, 2 and 5, and the blood plasma analysed for T. Rams not previously exposed to ewes stimulated more ewes to exhibit oestrus by day 35 than rams previously exposed to ewes (46% vs. 30%; P<0.01). Ewes previously exposed and those not exposed to rams responded similarly to ram stimulation, and by day 35 there was no difference in percentage of ewes mated. Both oestrus and anoestrus ewes increased T in rams on day 0. On day 2, T had returned to day -1 levels for rams with anoestrus ewes but increased further in rams with oestrus ewes (0.67 vs. 2.34 ng/ml; P<0.05).

The effect of secondary compounds of birdsfoot trefoil and red clover on dairy cow grazing preferences - Poli CHEC; Hodgson J; Arnold GC; Cosgrove GP (Proceedings of the New Zealand Society of Animal Production, 1998)
The responses of grazing animals to specific plant secondary compounds were examined in trials in which dairy cows grazed spaced plants of either birdsfoot trefoil (Lotus corniculatus L.) with high and low concentration of extractable condensed tannins (2.54 and 0.62 % in the DM respectively for high and low tannin genotypes), or red clover (Trifolium pratense L.) with high and low formononetin concentration (0.68 and 0.29 % in the DM respectively for high and low formononetin genotypes). Plants were established in 4 linear sequences of 26, each providing three blocks (replicates) of balanced sets of 2 plant species, 2 concentrations of test components, and plants either not trimmed or trimmed to minimise physical differences between genotypes within species. The sequences were grazed by four trained cows and selective behaviour was determined by the number of grazing bites per plant. Observations were repeated in March (P1) and April (P2). On average, animals grazed more on non-trimmed than on trimmed plants (7.6 vs 3.1 ± 0.711 bites/plant in P1, P=0.0001; and 8.4 vs 3.6 ± 0.858 bites/plant in P2, P=0.0002), but did not show clear discrimination between red clover and lotus (6.3 vs 4.4 ± 0.711 bites/plant in P1, P=0.053; and 6.3 vs 5.7 ± 0.858 bites/plant in P2, P=0.620). However, though the distribution of bites between red clover plants with high and low formononetin was similar (7.2 vs 5.5 ± 0.76 bites/plant in P1, P= 0.130; and 7.3 vs 5.3 ± 1.08 bites/plant in P2, P= 0.191), they showed strong preference for low condensed tannin concentration in lotus ( 2.1 vs 6.6 ± 1.11 bites/plant in P1, P= 0.0068; and 3.9 vs 11.1 ± 1.35 bites/plant in P2, P= 0.069).

Effect of sire genotype on lamb growth and carcass productivity - Nicoll GB; Skerritt JW; Dobbie JL; Grimwood TJ (Proceedings of the New Zealand Society of Animal Production, 1998)
The growth and carcass traits of 774 lambs out of Romney ewes and sired by Suffolk (S), Landcorp Lamb Supreme (LS), Texel (T) and Romney (R) rams were compared when slaughtered on five occasions (groups 1 to 5): November 1995, February, March, May and July 1996. Forty carcasses per slaughter group were dissected into commercial cuts of saleable meat, fat trim and bone. S- and LS-sired lambs had heavier pre-slaughter liveweights than T-sired lambs (38.4 ± 0.27, 38.5 ± 0.26, vs 36.3 ± 0.27 kg respectively; P<0.001), which in turn were heavier than R-sired lambs (35.0 ± 0.29 kg; P<0.001). S-sired lambs had heavier hot carcass weights than both LS- and T-sired lambs in slaughter groups 4 and 5 (+0.9 to +1.9 kg; P<0.01); R-sired lambs were significantly lightest in all slaughter groups (-0.7 to -3.9 kg; P<0.05). S- and R-sired lambs had greater adjusted GR tissue depths than LS-sired lambs in later slaughter groups. T-sired lambs were generally intermediate between LS- and R-sired lambs. R-sired lambs produced less weight of saleable meat than S-, LS- and T-sired lambs (by 1.4 to 1.7 kg; P<0.01). Lambs sired by Landcorp’s terminal sire breeds out-produced those sired by the company’s maternal R sire breed. S-sired lambs exhibited rapid growth early in the season, but increased fat levels later in the season compared with LS-and T-sired lambs.

Effect of sperm dose, diluent type and timing of insemination on pregnancy rates in sheep. - Smith JF; Parr J; Murray GR; Clarke A; Oliver JE; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1998)
Low sperm numbers and ambient temperature storage are two important factors in the successful AI system for dairy cattle in New Zealand. Similar technologies with ram semen are required before the establishment of a similar AI system within the NZ sheep industry is feasible. A trial involving a total of 1200 Romney ewes was conducted in April 1997 to examine the effects of inseminate dose (50, 25, or 5 x 106 sperm) of semen held for up to 9 h at 20°C in two diluents (RSD-1 and Tris + egg yolk). In the first half of the trial ewes were laparoscopically inseminated with semen from Finn rams at set times (49 and 56 h) after CIDR removal, while in the second half of the trial ewes were inseminated with semen from Romney rams following the detection of oestrus, after CIDR removal, resulting in insemination times of 26, 44 and 49 h post removal. Returns to service in the cycle following AI were recorded and ewes were scanned for pregnancy 50 days post AI. There was a significant difference between ram breeds in pregnancy rate (Finn 63.2 % v Romney 50.2 % ; P<0.05). There were no effects of inseminate dose nor of diluent. Time to onset of oestrus was affected by ewe live weight (P<0.05) with the heavier ewes showing a trend for an earlier onset but there was no overall effect of ewe weight on fertility. The effect of time to onset was reflected in an effect of time from CIDR removal to AI in the second half of the trial, with ewes AI’d within 30h of CIDR removal having a 10% lower fertility. These results indicate that acceptable fertility can be achieved with semen dose rates 5 to 10 fold less than normal, thereby increasing the number of inseminations available per ejaculate. Improved synchrony methods seem imperative to obtaining better fertility from AI.

The effect of stage of lactation and season on milksolids response to supplementary feeding of dairy cows. - Penno JW; Holmes CW; MacDonald KA; Walsh BJ (Proceedings of the New Zealand Society of Animal Production, 1998)
A factorial design was used to determine the effect of offering cows (n=8) in early, mid, and late lactation 50 MJME/cow/day of rolled maize grain (T2) or a nutritionally balanced supplement (T3) in spring, summer, autumn and winter at a restricted pasture allowance. The average milksolids production of the early, mid and late lactation groups was 1.16, 1.10, and 0.96 kg MS/cow/day (± 0.013), respectively. When compared to a non-supplemented control (T1), offering T2 and T3 supplements increased MS production from 0.91 to 1.14 and 1.13kg MS/cow/day (P<0.01), respectively. The milksolids responses to T2 was 150g MS/cow/day greater in summer and winter than in spring and autumn (P<0.05). Stage of lactation, or form of supplement, had no effect on milksolids response (P>0.05). These results suggest that the milksolids response to supplementary feeding was determined by the extent supplementary feeding increased total ME intake.

Effect of zinc oxide treatment for facial eczema on the copper status of Romney sheep grazing ryegrass pastures - Rounce JR; Knowles SO; Grace ND; Lee J (Proceedings of the New Zealand Society of Animal Production, 1998)
The copper (Cu) status of grazing Romney sheep was monitored following treatment with zinc oxide (ZnO). In a series of experiments sheep of various ages were treated with ZnO as either an oral drench weekly for one year, or as an intraruminal controlled release bolus (Time CapsuleTM , AgResearch) once (on day 0) or twice (on day 0 and 40), in two consecutive years. Measurements of Cu status included Cu concentrations in liver, kidney and muscle in all animals, and liver metallothionein (MT) in sheep dosed with ZnO orally. Drenching of two-year old wethers with 12 g ZnO/week for 52 weeks did not significantly change Cu liver concentration compared to untreated control animals (mean ± SD, 1.93 ± 0.88 and 1.67 ± 0.87mmol cu/kg FW, respectively). However, administering a single 42-day intraruminal ZnO bolus to six-month old lambs resulted in decreased liver Cu concentrations after 40 days (0.96 ± 0.06 compared to 1.33 ± 0.07 mmol Cu/kg FW in controls; P<0.001). When lambs which were growing at 100g/day were treated with a second ZnO bolus and evaluated after an additional 40 days, Cu liver concentrations were reduced by a further 20% but this change was not statistically significant (P=0.07). The variable effects of different forms of Zn treatment on liver Cu concentration are discussed in terms of duration of the dose, age of the animals, DM intake, initial Cu pool size in the liver, and Cu/Zn-binding MT. Under most conditions the benefits of ZnO as an effective facial eczema control are likely to outweigh any short term reduction in liver Cu.

The effects of a cation-anion balanced diet on calcium and phosphorus metabolism in growing lambs - Wilson KL; Min S; Revell DK; Lee J; MacKenzie DDS; Cottam YH; Davis SR (Proceedings of the New Zealand Society of Animal Production, 1998)
During the past decade, there has been renewed interest and research in the role of the dietary cation-anion balance (DCAB) in controlling Ca and P homeostasis. Two diets differing in DCAB (either high DCAB, 250 meq/kg DM, or low DCAB, -100 meq/kg DM) were fed to 10 Romney lambs. Feeding low DCAB decreased urine pH by 2.0 pH units; from 8.2 (SE=0.45) to 6.2 (SE=0.50), indicative of the anticipated changes in the ionic balance associated with alterations in the dietary CAB. Plasma concentrations of Ca and P, and whole-body Ca and P balance (intake-excretion) were similar for both groups of sheep. Reducing the dietary CAB caused a 7-fold increase in the urinary excretion of Ca (low DCAB 0.75 g/day vs high DCAB 0.11 g/day; P=0.001).The apparent absorption of Ca in the low DCAB and high DCAB groups were 1.6 and 1.3 g/day, respectively, although there was no significant difference between the two groups. These data indicate that lowering the DCAB increases urinary excretion of Ca of growing lambs without affecting Ca balance due to an alteration in the movement of Ca to and from bone. Similar changes in Ca absorption and utilisation have been observed in dairy cows, suggesting that the growing lamb is a suitable model for future studies in the regulation of Ca homeostasis in dairy cattle.

The effects of Insulin-nutrient supply interactions on ewe lactation - Back PJ; MacKenzie DDS; Davis SR; Harris PM (Proceedings of the New Zealand Society of Animal Production, 1998)
Six lactating abomasally cannulated ewes were subjected to a hyperinsulinemic euglycemic clamp with or without casein supplementation in a two period crossover design experiment. There was a significant response in milk (1169 ± 46 g/d vs 952 ± 46 g/d, P<0.001) and milk protein (66.4 g/d ± 2.7 g/d vs 54.2 g/d ± 2.7 g/d P<0.006), yield from casein supplemented ewes. There was no overall effect of the clamp on milk and milk protein yield, while the interaction was also non-significant. However, there was a significant reduction in feed intake (P<0.001) as the clamp continued, which may have compromised milk and milk protein response. There was also a significant period effect across all the measured parameters, which could also be a stage of lactation effect, due to the rapid decline of milk production during ewe lactation. In this study, in contrast to concentrate-fed cows, the utilisation of this technique did not increase milk protein yield in pasture fed lactating ewes.

Effects of oestradiol benzoate by injection at CIDR insertion for the treatment of postpartum anovulatory anoestrus in dairy cows - Verkerk GA; Taufa VK; Morgan S; Clark BA; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1998)
The effect of an intramuscular (im) injection of oestradiol benzoate (ODB) at insertion of an intravaginal progesterone-releasing device (CIDRTM, InterAg, NZ) during hormonal treatment for postpartum anoestrum in dairy cattle was investigated. Inclusion of injected ODB at CIDRTM insertion in synchronisation programmes for cycling cows can increase fertility, possibly by initiating an emergence of a new ovarian follicle wave with resultant improved oocyte competence. A total of 882 cows, of mixed age and breed from 18 herds, were examined and diagnosed as anoestrous during the week preceding each herd’s planned start of mating. Cows were allocated randomly as controls or to receive 0.5 or 1 mg ODB (Oestradiol Benzoate Inj., Intervet, Netherlands) by im injection at CIDRTM insertion. The device was removed after 7 days, and any cow which was not observed in spontaneous oestrus within 48 h received 1 mg ODB im (CIDIROLTM Injection, InterAg, NZ). Cows with an observed heat within 12 days of CIDRTM removal were defined as responders, and returns to service in the subsequent 30 days were recorded. There were no significant differences between the control, 0.5 and 1 mg ODB treatments for either the proportion responding (89.5%, 89.4% and 90.9%, respectively) or returning (52.3%, 50.3% and 55.4%, respectively); however the proportions of cows observed in spontaneous oestrus varied by treatment (P<0.01; 28.5%, 22.9% and 17.2% for control, 0.5 and 1 mg ODB treatments, respectively). Conception rates were not significantly affected by treatment (35.9%, 42.5% and 43.2% for control, 0.5 and 1 mg ODB treatments, respectively). Of cows which did not become pregnant to the induced oestrus, 21.7%, 20.7% and 29.9% for control, 0.5 and 1 mg ODB treatments respectively, returned to service with an interval of more than 24 days. These observations suggest that an injection of ODB at CIDRTM insertion may alter follicle wave patterns in cows with PPA, but that this may not result in increased conception rate, and might be detrimental to ovarian activity in a proportion of cows.

Effects of selection and crossbreeding on industry returns from whole milk powder, butter and casein in the New Zealand dairy industry - Lopez-Villalobos N; Garrick DJ; Spelman RJ; Holmes CW; Blair HT (Proceedings of the New Zealand Society of Animal Production, 1998)
The effects of selection and crossbreeding on New Zealand dairy industry return were evaluated with a deterministic simulation model over 25 years. Several crossbreeding strategies involving Holstein-Friesian (F), Jersey (J) and Ayrshire (A) cattle were evaluated. These strategies were straightbreeding, upgrading to F (UPGF), upgrading to J (UPGJ), upgrading to A, and two- and three-breed rotational crosses. Total production of milk, fat, protein, lactose and ash were calculated assuming that 12,000 kg dry matter/ha was eaten for 1,224,911 ha. Yields of standardised whole milk powder (WMP), casein and butter were calculated. For the base year all the protein was utilised in WMP and for subsequent years, some increases in protein were sold in the form of casein. Casein and WMP were valued at $6.00 and $3.31 per kg respectively over the 25 years, whereas butter was valued at $3.00 per kg for base year production levels and $0.45 per kg for marginal increases in production. Production for the base year was 9,874 million l milk, 467 million kg fat, 359 million kg protein and 464 million kg lactose which yielded 1,263 million kg WMP and 157 million kg butter for an industry return of $4,646 million. Relative to the base year, UPGF resulted in the largest increase in WMP (128 million kg, 10%), the lowest increase in casein (36 million kg) and increased returns by $639 million (14%). UPGJ resulted in the lowest increase in WMP (73 million kg, 6.0%), the largest increases in butter (67 million kg, 43%), casein (65 million kg) and returns ($662 million, 14%). Two-breed rotational (F,J) resulted in product flows for WMP and butter that were above the intermediate between UPGF and UPGJ but return that was equal to UPGJ. Selection within-breed in combination with crossbreeding can increase industry returns. However, the net financial outcome of all changes must be assessed taking into account farm expenses, income from culled stock and factory costs in processing milk with different composition in order to determine optimum crossbreeding strategies.

Effects of sire and body site on wool colour measurements in Romney x Perendale progeny - Wuliji T; Dodds KG; Andrews RN; Turner PR; Wheeler R (Proceedings of the New Zealand Society of Animal Production, 1998)
Six Romney rams were selected, three for "Bright" and three for "Yellow" wool, using estimates of breeding values for base wool colour. Six hundred Perendale ewes were randomly allocated to these rams in a single sire groups and joined for one mating cycle. Female progeny (n=280) were identified and grazed in one mob until weaning then split into two, one on Invermay and the other on Woodlands. Shoulder wool strip samples were collected at 3, 9, 12 months of age, two-tooth and as 2 year old ewes. The wool characteristics of yield, fibre diameter, resistance to compression and tristimulus colours were measured. No significant sire effect was found for tristimulus Y values at any sampling interval. A significant (P<0.05) tristimulus Y-Z difference was found for two tooth fleeces in progeny of Yellow sires compared with Bright (5.3 vs. 4.4 SED 0.4). Belly and back site wool was significantly (P<0.05) more yellow (Y-Z 7.8 and 6.1) than other body sites, belly wool was also lower (P<0.05) for brightness (Y 47.9) than other sites. The most significant source of variation in tristimulus Y and Y-Z values was contributed by body regions of fleece, emphasising the importance of effective skirting of fleeces.

Evaluating the business risk associated with feeding supplements to dairy cows on pasture - Laborde D; Shadbolt NM; Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1998)
The beta analysis technique provides a practical tool for evaluating the business risk associated with feeding supplements to dairy cows. The break-even cost, the expected profitability and the probability of making a profit can all be derived by predicting the marginal milksolids (MS) response, and applying prices for MS and supplements. The range of possible outcomes is simulated from specified maximum and minimum values, and the associated response distribution for each of these variables. The profitability of feeding maize silage on a market milk supply dairy farm was used to demonstrate the possible application of formal risk analysis to dairy herd management with a 50% spring: 50% autumn calving pattern. To be profitable, the marginal response to maize silage has to be maximised when no milk premium is paid, but, in the months when a premium is earnt, the risk of not making a profit is small.

Examination of selection index weights for lamb production - Skerritt JW; Amer PR; Nicoll GB (Proceedings of the New Zealand Society of Animal Production, 1998)
Economic values for lamb production have historically been derived with the assumption that lambs are slaughtered at a constant age. However, Landcorp Farming Limited slaughters lambs when they reach a set carcass weight. After weaning, heavier lambs are given preferential feeding and slaughtered when they reach a predicted carcass weight of 15kg. In this study index weights for weight of fat (FAT) and weight of lean (LEAN) in the carcass are calculated based on the different costs and returns associated with finishing lambs at a set weight. The nonlinear profit function was responsible for a positive index weight being derived for FAT. This result highlights the problems with using FAT and LEAN as selection criteria for lamb production. It is pointed out that FAT and LEAN are not breeding objectives for sheep production, and that it may be possible to use selection criteria better related to the profit function.

Exercise effects on muscle glycogen concentration in beef cattle - Lambert MG; Knight TW; Cosgrove GP; Anderson CB; Death AF; Fisher AD (Proceedings of the New Zealand Society of Animal Production, 1998)
Low ultimate-pH of beef is desirable because it increases shelf life and has beneficial effects on colour and tenderness. Industry recommendations are that beef animals are not exercised strenuously prior to trucking, as this may trigger depletion of muscle glycogen and lead to higher beef pH. In 2 experiments, 400-500 kg 18-month-old steers were exercised at a range of intensities up to 5 km distance at 8 km/hr. Biopsy samples from the longissimus dorsi muscle were taken and glycogen concentration measured. Although plasma lactate levels were elevated by exercise there was no significant depletion in muscle glycogen concentration (average 17.7 mg/g tissue). Depletion may have occurred had animals been heavier and fatter, or if the exercise regime had been more severe. Alternatively, it may be that at the level of exercise imposed (which was severe by farm-practice standards), animals also needed to be emotionally stressed in order to precipitate a depletion of glycogen, through a combination of muscle contractile and adrenergic reactions.

Experimental designs for Quantitative Trait Loci detection in the New Zealand dairy industry - Spelman R; Lopez-Villalobos N; Garrick D (Proceedings of the New Zealand Society of Animal Production, 1998)
Detection of loci that affect quantitative traits such as milk production has been undertaken with daughter and granddaughter designs in the N.Z. dairy industry. Two other experimental designs, selective DNA pooling of trait extremes and the use of first cross Holstein-Friesian–Jersey bulls, offer the opportunity to detect more loci than the current two designs. Selective DNA pooling involves the collective pooling of DNA from daughters at each extreme (high and low) of the trait distribution. A sire family of 100,000 daughters with DNA pools created from the top and bottom 1% of progeny pooled has the same power (probability of detection) as approximately 5,000 progeny being individually genotyped with less than 1% genotyping effort. Crossbreeding in the New Zealand dairy industry opens up the opportunity to identify QTL alleles that contribute to the genetic differences between the two breeds. Identification of breed specific QTL alleles can be achieved at a power of 90% based on some 600-1500 progeny from matings of F1 Holstein-Friesian x Jersey bulls to F1 cows.

Factors influencing the prevalence of postpartum anoestrus in New Zealand dairy cows - Rhodes FM; Clark BA; Nation DP; Taufa VK; Macmillan KL; Day ML; Day AM; McDougall S (Proceedings of the New Zealand Society of Animal Production, 1998)
The aim of this study was to determine the association between age, interval from calving (PPI) and breeding worth (BW) and prevalence of postpartum anoestrus (AA), as well their effect on response to hormonal treatment by anoestrous dairy cows. Individual cow details were collated from 6649 cycling and 2446 AA animals in 29 herds. Probability of AA was influenced by herd and was negatively related to PPI and age (p<0.001); but was not related to BW (p>0.05). Response of AA cows to treatment with progesterone and oestradiol benzoate was evaluated using a subset of 1482 anoestrous cows. Within 7 days of treatment, oestrus was detected in 87.1% cows and conception rate to insemination during this period was 42.2%. Oestrous response varied between herds but was not influenced by BW, PPI or age (p>0.1). Conception rate was positively related to PPI (p<0.001), but was not influenced by BW or age (p>0.1). It is concluded that in commercial dairy herds the likelihood of a cow being AA is greatest in young and recently calved animals, but is not influenced by breeding worth.

Future opportunities in livestock production and biomedicine from advances in animal cloning - Wells DN; Misica PM; Tervit HR (Proceedings of the New Zealand Society of Animal Production, 1998)
Recent international advances in animal cloning technology have enabled the production of offspring from cultured cells derived from either embryos, foetuses or adults. When the current nuclear transfer process becomes more efficient, there will be three main applications for agriculture. These include: (1) the rapid dissemination of animals with the desired genetic characteristics; (2) the use of cloning for phenotypic evaluation of animals; and most significantly, (3) the production of genetically modified animals. Nuclear transfer will be combined with gene targeting technology to introduce precise genetic modifications to the cultured cells in the laboratory, resulting in the production of cloned transgenic farm animals. It is anticipated that this will herald a new era in biotechnology, with opportunities to generate animals for various biomedical applications and with modified livestock production characteristics.

Genetic parameters for liveweight and live animal ultra-sound fat and eye muscle dimension in a synthetic terminal sire breed - Clarke JN; Nicoll GB; Mowat CM (Proceedings of the New Zealand Society of Animal Production, 1998)
During 1993-97, approximately 7000 lambs were weighed at weaning (WW), re-weighted (LW) and ultrasonically scanned for subcutaneous fat depth (FD) and eye muscle dimensions (depth (MD) and width (MW)) at 6 months of age. Animals belonged to Landcorp`s `Lamb Supreme` terminal sire breeding programme, derived in 1989-91 from mainly Romney ewes mated to Romney, Wiltshire, Coopworth, Texel and Poll Dorset sires selected for fast growth and leanness. Records representing the selection criteria were analysed by univariate and multivariate animal-model REML methods able to take account of the effects of selection on variance components. Heritabilities were higher for LW (0.33 ± 0.03) than WW (0.28 ± 0.03) and litter contributions (as a proportion of phenotypic variance) lower (0.29 ± 0.02 and 0.44 ± 0.02, respectively). Heritability estimates for all traits were similar in both sexes except for MW, which was higher in females (0.34 ± 0.05) than males (0.23 ± 0.05). Averaged across sexes, estimates were: FD (0.30 ± 0.03), MW (0.29 ± 0.04) and MD (0.33 ± 0.03), litter contributions being lower for FD (0.13 ± 0.02) than MW (0.22 ± 0.01) or MD (0.19 ± 0.02). MD was closely related genetically with MW (0.97 ± 0.01), but less closely associated with LW (0.44 ± 0.06) than was MW (0.57 ± 0.05). Both muscle traits showed similar genetic correlations with FD (0.48 ± 0.07 for MW; 0.43 ± 0.07 for MD). Parameter estimates indicated positive genetic trends for LW (regression of estimated breeding values on year of birth) more than two-fold higher than those previously published, and with little concomitant increase in FD.

Grain supplementation of finishing beef cattle - Boom CJ; Sheath GW (Proceedings of the New Zealand Society of Animal Production, 1998)
Low pasture quality in summer-autumn and feed deficits during winter are major constraints to achieving consistently high growth rates in beef cattle finishing systems. Two experiments were run to investigate the tactical use of grain supplementation as a tool to overcome performance constraints during these seasons. The first experiment was conducted during January-March (8 weeks) and involved 4 supplementation treatments: 0, 2, 4, and 6 kg grain supplement/hd/d. The second experiment was conducted during July-August (8 weeks) and also involved 4 supplementation treatments: 0, 1, 2, and 4 kg/hd/d. Rising 2 year steers were used in these experiments and pre- and post-grazing herbage masses were similar for all treatments within each experiment. During the summer experiment, steer liveweight gains were 0.05, 0.43, 0.65 and 0.80 kg/hd/d for the 4 supplementation levels respectively. During the winter experiment, average liveweight gains were 0.89, 1.08, 1.30 and 1.35 kg/hd/d. After grain supplementation ceased, liveweight advantages were eroded by compensatory gain occurring in the lower supplementation treatments. The average liveweight response to grain was similar in both experiments (0.18 kg liveweight gain/kg DM supplement), but was highest and most consistent at the 2 kg/hd/d supplementation rate. Acidosis was evident in 1 replicate of the highest supplementation treatment in each experiment. The use of a grain supplement can give reliable weight gain responses and could be valuable as a tactical tool to ensure that time and market bound supply contracts are fulfilled during difficult seasons. The use of this practice in systems that supply to commodity markets is unlikely to be economic.

Growth and carcass composition of Angus steers raised together from birth and managed on two post-weaning nutritional - Pleasants AB; Barton RA; Ball AJ; Oddy VH (Proceedings of the New Zealand Society of Animal Production, 1998)
Two groups of 33 Angus steers aged 270 days and weighing 179 ± 2.1 kg were allocated after weaning to 2 pasture regimes designed for high (H) and low (L) mean Liveweight. When the treatments finished after 138 days liveweights were 242 ± 3.7 kg (H) and 218 ± 3.7 kg (L). Both H and L groups were then grazed together on pasture until slaughter at 30 months of age. At slaughter fat depth at the 12th rib, weight of kidney and channel fat, ribeye area, and the trimmed fat, bone and lean (90% visual lean) were measured from the right side of the carcass. Carcass weight was the same for both treatment groups (258 ± 2.5 kg). The L group had faster liveweight gain than the H group for 283 days after treatment, but not thereafter. Steers from the L treatment had more kidney and channel fat (P<0.02). A significant (P<0.01) regression coefficient of 0.05 ± 0.019 for carcass weight on kidney and channel fat weight existed for steers in the H group, but not the L group. Rate of live weight gain before weaning was significantly (P<0.01) related to the weight of trimmed bone and lean at slaughter. Differences between animals in live weight gain at the end of the treatment period affected the weight of kidney and channel fat in the L group (P<0.01), and the weight of trimmed fat in the L group (P<0.05). These results are discussed in context of effects of growth rate on tissue development in cattle.

Growth curves and productivity of Holstein-Friesian cows bred for heavy or light mature live weight - Garcia-Muniz JG; Holmes CW; Garrick DJ; Lopez-Villalobos N; Wickham BW; Wilson G; Brookes IM; Purchas RW (Proceedings of the New Zealand Society of Animal Production, 1998)
This paper presents data for live weights (LW) from birth to maturity, and for yields of milk and milksolids (MSY) per lactation, from two lines of Holstein-Friesian cows bred for heavy (H) or light (L) mature LW. Compared with the Brody, Gompertz and Logistic functions, the Von Bertalanffy function provided the best fit to the LW data, and prediction from this function has been used in the following analyses. The breeding values (BV) for LW of the sires (H: 86.3 kg; L: 31.0 kg) and maternal grandsires (MGS) (H: 55 kg; L: 38 kg) used to develop the H and L LW lines were higher (P<0.001) for the H line than for the L line, and they were significantly associated with the actual birth weight (H: 41 kg; L: 35 kg) and mature live weight (H: 520 kg; L: 467 kg) of the cows. The heavy sires also had significantly higher BV for yield of milk (H: 1037 l; L: 737 l), milkfat (H: 33.0 kg; L: 27.5 kg), and milk protein (H: 31 kg; L: 22 kg), and the H cows produced more milk (H: 4708 l; L: 4323 l), and MSY (H: 364 kg; L: 348 kg) than the L cows. However, L sires had slightly higher (P = 0.07) value for Breeding Worth than the H sires (H:37; L:46), and there were only small differences in yields of milk or MSY between the two lines when these were expressed per kg of LW, per kg of LW0.75 or per tonne of dry matter required (H: 84 kg MSY/tonne DM; L: 87 kg MSY/tonne DM). The results indicate that the extra MSY by the H cows (+ 16 kg) almost compensated for the effect of their extra LW (+ 46 kg), so that the H cows were only slightly less efficient than the L cows, as predicted by their respective sire’s Breeding Worth.

Growth factors and their role in wool growth: a review - Nixon AJ; Moore GPM (Proceedings of the New Zealand Society of Animal Production, 1998)
Wool follicles develop as a consequence of interactions between cells of the epidermis and dermis during intrauterine life. Fibre growth in mature follicles is believed to be governed predominantly by exchanges of signals between these cells and the matrices in which they are embedded. Over the last decade, increasing numbers of growth factors have been implicated in such communications. In particular, these include members of the epidermal growth factor (EGF), fibroblast growth factor (FGF), insulin-like growth factor (IGF), and transforming growth factor-beta (TGF-β) families. Their actions have been shown in studies of skin cells in culture, gene manipulation and physiological experiments with isolated follicles or whole animals. A picture is beginning to emerge of orchestrated morphogenic, mitogenic and differentiative influences between follicle cells, and between cells and their extracellular matrices. When combined with growing technological capability, increases in our understanding of cellular signalling will present novel opportunities for the industry to usefully alter wool growth and fibre characteristics.

Herbage intake, grazing behaviour and feed conversion efficiency of lactating Holstein-Friesian cows that differ genetically for liveweight - Laborde D; Garcia-Muniz JG; Holmes CW (Proceedings of the New Zealand Society of Animal Production, 1998)
Two experiments were carried out to compare the feed conversion efficiency at high pasture allowances in early (EXP1) and mid-lactation (EXP2) of genetically heavy (H) or light (L) Holstein-Friesian cows (H = 487, L = 410 kg, P<0.001). Average milksolids (MS) yield was not significantly different in EXP1 (H = 1.73, L = 1.64 kg MS), but the H line had higher MS yield than the L line in EXP2 (H = 1.70, L = 1.54 kg/cow/day, P<0.001). The mean individual dry matter intakes (DMI, kg/cow/day), measured using the n-alkanes technique, were higher for H cows in both EXP1 (H = 15.5 and L = 13.9; P<0.05) and EXP2 (H = 12.2 and L = 10.8; P<0.05). However, herbage intake was not significantly different between the H and L cows when adjusted to a common MS yield. Feed conversion efficiency (g MS/kg DMI) was slightly higher for the L cows during EXP1 (H = 114, L = 120, P = <0.1), but not different for H and L cows during EXP2 (H = 144, L = 143). The calculated bite size of the H cows was on average 0.095 g DM/bite (pooled for the two experiments) heavier (P<0.05) than that of the L cows, but the L cows showed a consistently faster rate of biting than the H cows (H = 51, L = 56 bites/min, P<0.05). Although the H cows had higher MS yield than the L cows, especially in EXP2, the higher MS yield was not associated with increased efficiency, presumably because the H cows required more energy for maintenance than the L cows.

Iodine deficiency: an emerging problem in New Zealand sheep flocks. - Sargison ND; West DM (Proceedings of the New Zealand Society of Animal Production, 1998)
Iodine supplementation before mating had a significant positive effect on ewe fertility in a Manawatu Romney flock, with 14% more lambs born to supplemented than to control mixed aged ewes. The survival of newborn lambs was enhanced in the iodine-supplemented group when compared with the control group, accompanied by a significant difference between the thyroid:body weight ratios of dead newborn lambs in the supplemented and control groups (0.28 and 0.48 g/kg respectively)(p=0.005). During the spring of 1997, high perinatal lamb mortality rates (25%, 50% and 66%), despite favourable lambing weather conditions and adequate ewe nutrition throughout pregnancy, were investigated in three other Manawatu sheep flocks. The mean lamb thyroid:body weight ratios of dead newborn lambs were greater than 0.4 g/kg and hyperplastic colloid goitre was identified histologically. Goitrogens in the pasture were believed to be an important predisposing factor. Modern varieties of white clover present in New Zealand pastures contain extremely high concentrations of thiocyanate goitrogen precursors, therefore, iodine deficiency may be an emerging problem.

Management decision rules to optimise milksolids production on dairy farms - MacDonald KA; Penno JW (Proceedings of the New Zealand Society of Animal Production, 1998)
A review of grazing management research has provided a series of decision rules for the management of seasonal calving pastoral dairy farm systems. These rules have been used at the DRC No. 2 Dairy to remove subjectivity from the management of farm systems research. Cows are dried off with sufficient time for second calvers and mixed age cows to achieve condition scores of 5 and 4.5 by 1 June. Target pasture average herbage mass at calving is 2200 kg DM/ha. Optimum grazing management during autumn/winter, spring and summer has been shown to increase milksolids production by 29, 70 and 41 kg MS/ha, respectively. Grazing management during late spring must meet the dual objectives of generously feeding the herd, while maintaining pasture quality. Conserved pasture supplements should be fed in late autumn/early winter to meet cow condition, grazing management, and herbage mass objectives. Substantial increases in animal productivity can be achieved by sound farm management during periods of feed deficit.

Manipulating patterns of ovarian follicle development in cattle with progesterone and gonadotrophin releasing hormone to produce oestrous cycles with two or three follicle waves - Clark BA; Rhodes FM; Burke CR; Morgan SR; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1998)
This study tested the hypothesis that oestrous cycles with two follicle waves created using progesterone, could be converted to oestrous cycles with three follicle waves using gonadotrophin releasing hormone (GnRH). Oestrus (Day 0) was synchronised in 24 Friesian cows. On Day 2, a progesterone containing device (CIDR) was inserted into the vagina of 16 cows for 10 days. Eight of these animals received 8µg of buserelin (GnRH) at device removal. Eight untreated animals formed the Control group. Daily transrectal ultrasonography showed that the oestrous cycles of the cows treated only with a CIDR device had two ovarian follicle waves compared to 1/8 in CIDR+GnRH and 3/8 in Control groups (p<0.01). The average length of the oestrous cycle was shorter in the CIDR-only group (19.3 ± 0.5 days), compared to the CIDR+GnRH (20.9 ± 0.2 days) and Control (22.3 ± 1.1 days) groups (p<0.05). These results demonstrate that strategic administration of GnRH can convert progesterone induced two-wave oestrous cycles into a three-wave pattern.

Mature Merino ewe production performance in an ultrafine fibre diameter selected and a control flock - Wuliji T; Dodds KG; Andrews RN; Turner PR (Proceedings of the New Zealand Society of Animal Production, 1998)
Mature Merino ewe data (1988 to 1995) from 1407 ultrafine (UF) fibre diameter selected and 249 random controls (CF) totalling 3213 and 765 records respectively were analysed. Mean fibre diameter (FD) was significantly (P<0.001) lower in UF compared with CF (17.7 mm vs. 20.0 SED 0.04). Mean FD decreased in UF adult ewes by 0.16 um (±0.02) per year relative to CF. There were no differences for autumn live weight but UF was significantly lower for spring live weight (P<0.05) and fleece weight (P<0.01) and higher for fleece yield (P<0.01) than CF. There were significant (P<0.001) age effects for all of these traits. For those ewes born during the project (1990-1994), the number of lambs born per ewe was slightly higher for CF than UF (1.17 vs. 1.14 SED 0.04) but not significant. CF wool had greater tensile strength, bulk and yellow but lower crimp frequency (all P<0.01) than UF wool. Selection for ultrafine wool in Merino sheep has shown FD was significantly reduced without negative effect on liveweight and reproduction.

Milk progesterone concentrations at selected times following oestrus and insemination in relation to the success of pregnancy - Verkerk GA; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1998)
Positive relationships between concentrations of progesterone in milk and subsequent pregnancy rates suggest that measurement of milk progesterone concentration at selected times following insemination may facilitate identification of cows for strategic progesterone supplementation to enhance the probability of pregnancy. This study investigated some factors associated with variation in milk progesterone concentration. Following a standard oestrus synchronisation treatment with CIDR-BTM devices (InterAg, NZ), cloprostenol (Estroplan injection, Parnell Laboratories NZ Ltd, NZ) and oestradiol benzoate (CIDIROL Injection, InterAg, NZ) every cow artificially inseminated (AI) at 72 h after CIDR-BTM withdrawal (Day 0) was enrolled in the trial. Milk samples (fore-milk: Herd 1, n = 153, Holstein-Friesian; HF; composite: Herd 2, n = 50 HF and 76 Jersey; J) were taken 4, 8 and 22 days after AI to measure milk progesterone concentration. Pregnancy to the insemination was confirmed by rectal palpation 60-70 days later. Lower milk progesterone concentrations were found in fore-milk (Herd 1) than composite samples (Herd 2), but followed a similar pattern of change throughout Days 4, 8 and 22. Neither return to service, nor pregnancy status was associated with altered milk progesterone concentration on Days 4 or 8, but levels on Day 22 were higher (P<0.001) in pregnant cows. Mean milk progesterone concentrations were higher (P<0.001) in J than HF in Herd 2 on Day 8. Absolute milk progesterone concentration on Day 4 or 8 following AI did not predict the probability of pregnancy establishment, but the difference between milk progesterone concentration in the two samples was of predictive value on a herd, but not an individual cow, basis. Milk collection methods and breed effects need to be considered when developing milk progesterone concentration as a predictor of pregnancy establishment. Although the non-parametric analyses showed that non-pregnant animals tended to have lower milk progesterone concentration, the requirement for analysis of at least two samples will limit its use as a practical means to identify the subset of cows for which strategic progesterone supplementation might be considered.

Modelling the Feed Requirements of Cross-Bred Sheep - Brookes IM; Lowe KI; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1998)
Feed requirements of flocks of ewes from Romney dams mated to either Romney , Border x Dorset, Finn x Texel, or Texel x Dorset sires (R, BD, FT, TD), were estimated from assumed profiles of live weight and reproductive performance. These were constructed by extrapolating data collected from four flocks of 500 ewes each, born in 1994 and run under a common management system at Limestone Downs (a large Waikato sheep/beef property). Annual feed requirements for R, BD, FT and TD ewes (plus 25% replacements) were estimated to be : 670, 809, 766 and 740 kg DM/ewe; equivalent ewe numbers for the same annual intake: 1000, 829, 875 and 906 ewes; g lamb weaned/kg DM consumed: 37, 43, 47 and 40 g/kg DM. Live weight and reproductive profiles for ewes sired by East Friesian rams were also constructed by extrapolating data from East Friesian-cross ewes born at Limestone Downs in 1996 and mated as hoggets in 1997. Estimates of annual feed intakes, equivalent ewe numbers and g lamb weaned/kg DM consumed for East Friesian-cross ewes (plus 25% replacements), mated first as hoggets (EFH) were: 925 kg DM/ewe, 725 ewes and 56g/kg DM; or mated first as two-tooths (EF): 907 kg DM/ewe, 739 ewes, and 50g/kg DM. The increased feed demand for high producing ewes occurred mainly from late pregnancy until weaning.

Monitoring some muscoid fly populations on Massey University sheep farms in the Manawatu - Cottam YH; Blair HT; Potter MA (Proceedings of the New Zealand Society of Animal Production, 1998)
Over three summers (1993-94, 1996 and 1996-97), four fly-traps were placed at each of two locations on Massey University farms. Caught flies comprised eight species, of which four are commonly involved in flystrike. Australian sheep blowfly (Lucilia cuprina) numbers caught varied dramatically between years. At the season peak, numbers in 1996 and 1996-97 were three and one and a half times higher, respectively, than in the first year. Average weekly fly catch increased rapidly over a 2-3 week period from near zero to a peak (in years 1996 and 1996-97) of about 30 flies for L. cuprina and from near zero to a peak (in 1996-97) of about 75 flies for Chrysomya rufifacies in February/early March. Peaks presumably reflected emergence of adult flies from the previous year’s pupae that overwintered in the soil. Five of the eight species showed a second peak about four weeks after the first. The second peak most likely reflects emergence of a second generation. Minimum temperature explained a significant proportion of variation (up to 48%) in fly numbers. Rainfall and wind run were less important. Further work is required to provide robust indicators of potential rises in fly numbers.

New Zealand beef industry structure and opportunities to improve income - Charteris PL; Garrick DJ; Morris ST (Proceedings of the New Zealand Society of Animal Production, 1998)
As a product, beef can be classified as suiting table or processing requirements. The aim of this study is to quantify the volume and value of table and processing beef arising from herds of beef or dairy origin to identify opportunities for increasing industry revenue from improving table beef harvest relative to processing products. A deterministic model was developed to calculate product flows and income from processing and table beef derived from beef and dairy herds over a 20 year horizon. The dairy herd contributed 52% of beef, 60% of processing grade beef and 45% of total beef income. Processing grade beef comprised 58% of total product by weight. Beef-breed steers and Holstein-Friesian (F) bulls were the largest contributors of any cattle class to table and processing grade beef and total industry revenue. Improving the harvest of table beef by 1% from F bulls would increase beef industry revenue by 0.7%, a similar increase in revenue that could be achieved from beef-breed steers. The relative contribution of beef and dairy origin cattle to beef revenue is insensitive to table beef premiums over processing beef. Any improvement strategy within the beef industry should be considered with dairy-origin beef animals in mind.

Once-Daily Milking of Dairy Cows : An Appraisal - Davis SR; Farr VC; Stelwagen K (Proceedings of the New Zealand Society of Animal Production, 1998)
Once-daily milking offers the opportunity for a quantum change in the operation of the dairy farm. In particular, once-daily milking provides the major opportunity to reduce costs and increase labour productivity. New Zealand cows (particularly Jerseys) already possess an advantage in favour of once daily milking - that they produce a relatively concentrated milk and therefore have the capacity to accumulate >24 hours-worth of milk production. Nevertheless, short-term trials indicate an average production loss of 21% for once-daily relative to twice-daily milking. Full-lactation trials suggest greater losses of 35-50%, although the productivity of commercial farms milking once-daily throughout lactation is consistent with much smaller losses. There is evidence that cows can adapt to longer milking intervals and this coupled with increased herd size and care to maximise milk removal may restrict yield losses on the farm to less than 10%. Apart from the production loss, other negative consequences of once-daily milking include changes in milk composition, a reduction in milk processing quality and increased somatic cell count. Further, it is not known to what degree, if any, cow comfort is compromised by once-daily milking. If it becomes possible to identify more tolerant breeds or individuals, it may be feasible to reduce milk yield losses still further and ameliorate the changes in milk composition.

Out-of-season breeding in thyroidectomized red deer hinds - Anderson GM; Barrell GK (Proceedings of the New Zealand Society of Animal Production, 1998)
Thyroid hormones are required for the neuroendocrine processes that cause the onset of the non-reproductive state each spring in red deer. To evaluate the feasibility of achieving out-of-season breeding using thyroidectomized (THX) hinds and a THX stag, oestrous behaviour and ovulation were compared in THX (n=9) and thyroid-intact control hinds (n=6) following synchronization of oestrous cycles with CIDRs and joining with a THX, vasectomized stag in the breeding and non-breeding seasons. In the control group, oestrus and ovulation were recorded in all (100%) and none (0%) of hinds during May (breeding season) and October (non-breeding season) respectively (P<0.05), however in THX hinds oestrus and ovulation occurred in a proportion of the animals (33-55%) and this incidence was not affected by season (P>0.05). Time of onset after synchronization and duration of oestrus were not significantly affected by thyroidectomy or season (P>0.05). To determine if pregnancy could be established in THX hinds in the non-breeding season, all 15 hinds were synchronized for oestrus using CIDRs plus 200 I.U. PMSG and joined with a fertile, THX stag in early December. Any hinds not mated on this occasion were resynchronized using CIDRs plus 400 I.U. PMSG and again joined with a fertile, THX stag. While the lower dose of PMSG was generally ineffective in inducing oestrus (i.e. only 2 THX hinds mated), 50% of control and 71% of THX hinds which received 400 I.U. PMSG exhibited overt oestrus. In all, seven out-of-season calvings (3 from thyroid intact and 4 from THX hinds) were obtained from 10 matings (all 3 unsuccessful matings occurred in THX hinds). These results imply that although thyroid gland secretions switch off reproductive activity at the end of the breeding season, they do have a supportive role in the expression of overt oestrus and occurrence of ovulation.

Ovarian volume is a predictor of the resumption of spontaneous oestrous cycles but not the response to the treatment of anoestrus. - Nation DP; Rhodes FM; Day AM; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1998)
This study examined the use of a classification system for ovarian activity as a predictor for both the spontaneous resumption of oestrous cycles and for reproductive per-formance after treatment for anoestrus.

A participatory evaluation of out-of-season beef cattle finishing systems in the lower North Island. - Sherlock TJ; Parker WJ (Proceedings of the New Zealand Society of Animal Production, 1998)
Beef cattle slaughter in New Zealand continues to be strongly seasonal, despite various initiatives by meat processing companies to alter the pattern of supply of cattle for slaughter. The farmer`s perspective of out-of-season (OOS) production systems (August -October supply) and the biological and financial feasibility of these was investigated through a participatory approach to farm system modelling. Three case farms were modelled using STOCKPOL and alternative cattle policies that provided a greater proportion of cattle for slaughter in OOS and shoulder (November - December and June - July) months were investigated with the farmers. Even with premiums 20% above schedule, farmers were unwillings to change policies to OOS. They were concerned about increased business risk, poorer feed quality, increased pasture pugging, greater workload over the busy lambing/calving period, poorer overall suitability to the property and conflict with personal preference. They were more receptive to policies that would increase shoulder production and this factor combined with off-farm improvements in technology for delivering fresh products to overseas destinations may be sufficient to gain new or greater access to high value markets.

Performance of Romney and One-Quarter Merino x Three-Quarters Romney sheep on Wanganui hill country - Everett-Hincks JM; Wickham GA; Blair HT (Proceedings of the New Zealand Society of Animal Production, 1998)
The performance of hoggets of part-superfine-Merino ancestry born in 1994 and 1995 were compared with straightbred Romneys (R) in a highly selected nucleus flock on a hill country property, near Wanganui. All animals were born to R ewes. In addition to R, ½ Merinos (½ M) were born in 1993 and ¼ Merino (¼M) in 1994 and 1995. The ¼M and R sheep born in 1994 did not differ significantly in hogget greasy fleece weight, live weights, growth rates, or faecal egg and nematode counts. Midside fleece samples collected at two-tooth ewe shearing in late February 1996 showed that the ¼M sheep were finer, more yellow, more-bulky and had shorter wool than the R sheep. For ¼M and R sheep born in 1995, the ¼M genotype had a lower hogget greasy fleece weight, weaning weight and 12 month live weight. The ¼M hogget wool was finer, brighter, less yellow, bulkier and shorter than the R midside wool. Clean scoured yield was not significantly different.

Possible impact of New Technologies On Dairy Cattle Breeding - McClintock AE (Proceedings of the New Zealand Society of Animal Production, 1998)
The aim of this paper is to draw together a variety of existing and emerging technologies and to look at how they interact and how they may impact on genetic improvement.

Pregnancy diagnosis of twinning beef cows - Lambert MG; Perkins NR; Devantier BP; Knight TW; Betteridge K (Proceedings of the New Zealand Society of Animal Production, 1998)
Technology now exists to make beef cows twin-pregnant. Accurate detection of pregnancy status is a prerequisite for differential management of twin and single-bearing cows. Calving outcome for about 50 beef cows was compared with predicted outcome by foetal counting using transrectal ultrasonography at day 50-70 of pregnancy, and veterinary palpation to confirm pregnancy at day 111-156. The trial ran for 4 annual calvings, and different combinations of scanning operator and equipment were used in each year. Overall accuracy of prediction of calving outcome ranged from 74-94%, and did not differ for cows carrying singles or twins. Prediction accuracy was highest in the 2 years where scanning equipment provided a high degree of visual detail, and the operator was experienced in distinguishing foetal abnormalities. It was concluded that the combination of early foetal counting using ultrasound, and later determination of wet/dry status by palpation, could lead to levels of accuracy close to those being achieved by competent commercial scanning operators for sheep.

Preliminary results of selecting sheep for resistance or susceptibility to ryegrass staggers - Morris CA; Towers NR; Amyes NC; Wheeler M (Proceedings of the New Zealand Society of Animal Production, 1998)
Ryegrass staggers (RGS) is a neurotoxic disease in ruminants caused by the mycotoxin lolitrem B, found in endophyte-infected swards of perennial ryegrass (Lolium perenne L.). This paper reviews genetic studies on the incidence of RGS at Ruakura, and the early responses to selection achieved since 1993. Using a coarse 0 or 1 criterion only, the incidence of RGS each year was recorded on weaned lambs (born in 1988-92), 2-tooths and all mixed-aged ewes, between January and March of each year 1989-93. Clinical cases of RGS occurred in 17 of 25 contemporary groups, with incidences per group up to 0.16. With 3587 records from 2307 animals representing 232 sires, animal-model restricted maximum likelihood estimates of heritability and across-year repeatability for RGS incidence were 0.068 ± 0.028 and 0.24 ± 0.05 respectively. Breeding value data were used to screen ewes and 2-tooths in 1993 into resistant and susceptible selection flocks, and to allocate elite rams for mating. Over the 1993-97 mating years, 14 and 12 rams have been used in the two flocks, respectively (11 of these twice or more). There was no significant effect of gender on incidence of RGS. From the most recent completed recording year (i.e. 1996-born lambs), 82 resistant-flock and 56 susceptible-flock animals had RGS incidences of 0.20 and 0.75 respectively (P<0.001). One hundred and eighty-five first-crosses between the two selection lines were also generated in 1996 and 1997, which may eventually provide more evidence on the mode of inheritance. The selection flocks are being continued. The selection response so far indicates that genetic differences in RGS susceptibility can be achieved while using recording under extensive conditions.

Prevalence of clinical mastitis in 38 Waikato dairy herds - McDougall S (Proceedings of the New Zealand Society of Animal Production, 1998)
The apparent prevalence of clinical mastitis was determined in 38 spring calving dairy herds as part of a larger field trial conducted on behalf of Boehringer Ingelheim NZ Ltd between the 8th of July and the 21st of August, 1997. A total of 798 quarters from 595 cows were diagnosed by herdowners as having clinical mastitis. Bacterial culture was performed on all clinical quarters and antibiotic sensitivity testing was performed on selected bacterial isolates. Clinical mastitis was diagnosed in an average of 10.0% (± 0.8%, range 0.9% to 21.4%) of calved cows within the herds. No bacteria were cultured from 28.2% of clinical quarters. Of the quarters from which bacteria were cultured, 74.7% were Streptococcus uberis, 10.2% were coagulase negative staphylococci, 4.7% were Coliforms, 4.1% were Streptococcus dysgalactiae, 2.9% were Staphylococcus aureus and 3.3% were other species of bacteria. Penicillin resistance was detected in 25% of 44 Staphylococcus aureus isolates, 0% of 10 Streptococcus uberis isolates and 100% of 12 E. coli isolates.

Productivity and Profitability of Twinning Beef Cows - Smeaton DC; Clayton JB (Proceedings of the New Zealand Society of Animal Production, 1998)
Twinning Hereford x Friesian beef cows were run in farmlets with breeding ewes at Whatawhata Research Centre. The additional inputs and outputs of twinning cows were compared with those of single calving treatments. This was carried out in a farm systems environment so that the feed-back mechanisms inherent in biological systems could operate. Typically, the twinning beef cows lost 15% of their foetuses during pregnancy and had (in the most recent year) a calf survival rate of 80%. Comparable figures for single calving cows were 5 and 95% respectively. Twin calves weighed 200 kg at weaning compared to 240 kg for singles. The twin cow farmlets required 250 kg extra DM/cow and 5.7 extra hours of labour/cow at calving. The sheep were not measurably affected by cow treatment. Gross margin analyses using these and other trial data indicated that twinning cows were $44/cow less profitable than single cows. Further analyses showed however, that the twinning cow system would breakeven with the singles if any one of the following changes were possible, (1) twin calf wean weight 220kg, (2) twin calf survival 89%, (3) twin foetal loss 5%, (4) labour differences dropped from 5.5 (above) to 2.1 hours/cow. When all the breakeven values were assumed to have occurred at the same time, twin cows were $120/cow more profitable than single cows. This is the money available to pay for extra risk and the extra cost of getting a cow twin pregnant (at day 60) compared to single pregnant.

Prolactin receptors are highly expressed in wool follicle dermal papillae. - Nixon AJ; Choy VJ; Ford CA; Pearson AJ (Proceedings of the New Zealand Society of Animal Production, 1998)
Seasonal variation in wool growth has major impacts on production and fibre characteristics. These changes in wool follicle output are driven, at least in part, by circulating prolactin. We therefore localised prolactin receptors (PRLR) in skin from Wiltshire sheep over a wool follicle cycle induced by prolactin. PRLR expression was visualised by in situ hybridisation, immunocytochemistry and radioligand binding. The three approaches showed concordant distributions of PRLR and its mRNA. PRLR mRNA was most abundant in the dermal papilla, but also evident in the outer root sheath, hair germ, skin glands and epidermis. Expression in the hair germ was up-regulated in telogen. Location of PRLR in the dermal papilla and outer root sheath indicates action of prolactin directly on the growth controlling cells within wool follicles. These spatial and cycle-related patterns of PRLR expression contribute to the growing knowledge of the control of wool growth and its application in the wool industry.

Rates of recovery of milk yield and composition following milking intervals of varying length - Farr VC; Stelwagen K; Davis SR (Proceedings of the New Zealand Society of Animal Production, 1998)
In order to examine the rate of recovery of milk yield and composition following an extended milking interval, 20 cows were milked out with the aid of oxytocin and subjected to single intervals of either 16, 24, 32 or 40h. Cows were then milked frequently with the aid of oxytocin during the subsequent 26h. Milk secretion rate was depressed to 67 and 56% of pre-treatment (twice-daily milking) rates by the 32 and 40h treatments, and rates of recovery were slow, extending beyond 26h post-treatment. Milk fat and protein contents did not differ significantly among treatment groups while lactose content was reduced by the 32 and 40h intervals, recovering by 26h post-treatment. It was concluded that the udder is particularly sensitive to milk accumulation beyond 24h and that this leads to impairment of the ‘synthetic machinery’ in the udder. The prolonged effect on milk lactose concentrations with the longer intervals suggests that there was a sustained change in the integrity of tight junctions between secretory cells, leading to increased permeability of the mammary gland. Rates of recovery of yield and composition were relatively slow, taking >24h in spite of enhanced rates of milk removal.

Recent improvements in flow cytometric sorting efficiency of X and Y-chromosome bearing sperm of domestic animals: a review. - Gurnsey MP; Johnson LA (Proceedings of the New Zealand Society of Animal Production, 1998)
In mammals the only method known to reliably separate X and Y sperm for producing offspring of a specific sex is flow cytometric sorting. This method is based on the observation that X-chromosome bearing sperm of domestic animals contain 3.5-4.2% more DNA than Y-chromosome bearing sperm. Relative DNA content is determined by quantitative staining with Hoechst 33342 and DNA content measured using a modified cell sorter. The major constraint to widespread application of this technology has been the slow sorting rate. Using modified standard speed cell sorters, sample flow rates average 2,000 sperm/sec with 25-35% orientation. Recently, a high speed sorter (MoFlo®) modified for sperm sorting has been used and increases sorting rate by approximately 5-fold. Further, an orienting nozzle has been developed which increases the percentage of sperm that are orientated thus increasing the sort rate by a further 2 to 3-fold. Combined, these improvements have increased the production of sorted sperm from approximately 0.3 x 106/h with conventional sorters to at least 4 x 106/h with the high speed sorter. Preliminary testing suggests that purity of sort and sperm viability are not compromised by increased sorting rates. Pregnancies have been established in pigs and cows with sorted sperm from a modified MoFlo fitted with a novel nozzle. The improvements outlined here greatly enhance the Beltsville Sperm Sexing Technology and make it realistic to consider trials using sex sorted sperm for conventional AI as well as deep uterine AI in cattle.

The relationship between carotenoid concentration and fat colour in beef carcasses - Knight TW; Death AF; Boom CJ; Litherland AJ (Proceedings of the New Zealand Society of Animal Production, 1998)
Relationships between carotenoid concentration, chromameter (L* a* b*), and subjective measurements of fat colour were calculated from 15 mobs of cattle. Carotenoid concentration accounted for 60% of the variation in b* (n=514), but b* accounted for only 16% of the variation in subjectively measured fat colour (n=732). Neither the inclusion of other variables (e.g. carcass weight or fat depth) nor transformation of the data substantially improved these relationships.

Relationships between laboratory measures of ram sperm competence and field fertility. - Smith JF; Parr J; Murray GR; Clarke A; McDonald RM; Duganzich DM (Proceedings of the New Zealand Society of Animal Production, 1998)
Previous work has show poor relationships between the maintenance of sperm motility and fertility after AI of ram semen. New laboratory tests of sperm competence have been developed but their relationship to fertility needs to be established. Two large scale trials involving the laboratory evaluation of straws of frozen semen from different rams and the field AI of ewes with the same batches of semen were conducted. In Trial A, 1671 ewes were AI`d with 52 batches of semen from 26 rams on 6 farms. In Trial B 6872 ewes were AI`d with 137 batches of semen from 34 rams on 25 farms. In Trial A, there was no linkage between farms while in Trial B the same batch was used on more than one farm and most farms had more than 1 batch from more than 1 ram. Laboratory evaluation involved: visual motility assessment post thaw and time taken to drop to 5% motility when incubated at 38°C, 8 parameters of velocity and direction of motility using CASA; % live and % acrosome intact and sperm concentration. These parameters were measured immediately post-thaw and in Trial B a repeat measurement was made after 6h at 38°C. In addition, in Trial A the relative IVF value was determined. In Trial A there were significant (P<0.05) between farm and ram within farm effects on fertility (% pregnant) but no ejaculate within ram effect. Significant (P<0.001) differences were seen in all semen parameters except initial motility, time to 5% and concentration. Parameters correlated with fertility were IVF and % live and together these accounted for 44 % of the variation. In Trial B, there were effects of farm on fertility (P<0.001) and breed of ram (P<0.05), residual ram variation was non-zero but not significant. There were significant differences between rams and between ejaculates within rams in concentration, visual motility, % live, velocity and directional parameters. The number of live and motile sperm inseminated was correlated (P<0.001) with fertility. Significant (P<0.05) correlations were also obtained between two CASA parameters; the % live and % visual motility, after 6h of incubation. Multiple regression equations were derived that accounted for between 62 and 75 % of the variation between rams.

Reproductive performance of Holstein-Friesian cows differing genetically in live weight - Laborde D; Holmes CW; Garcia-Muniz JG; Wichtel J (Proceedings of the New Zealand Society of Animal Production, 1998)
The reproductive performance of two genetic lines of Holstein-Friesian cows bred for heavy (H) or light (L) mature live weight (LW) was evaluated from 1992 to 1997. The interval calving to ovulation was shorter (P<0.05) for H cows (28 ± 3.2 days) than for L cows (L: 31 ± 2.5 days), but the difference between the lines in the interval calving-first heat was not significant (H: 50 days; L: 43 days). However, in the cows older than 2 years old, the H cows had a lower conception rate at first service than the L cows (H: 58% vs. L: 70%) which extended the conception and calving pattern of the H cows. The possible reasons for those differences in the reproductive performance are discussed as topics for further research.

Reticular Groove Contraction in Yearling Cattle Detected by Breath Test - McLeay LM; Carruthers VR; Neil PG (Proceedings of the New Zealand Society of Animal Production, 1998)
A novel method was used to detect the incidence of reticular groove contraction in yearling cattle. Following its oral administration, 13C octanoic acid is absorbed from the intestine, metabolised by the liver and the 13C label excreted in the CO2 of breath. Contraction of the reticular groove should result in a quicker and greater peak appearance of 13C in breath, than when swallowed material is delivered into the reticulo-rumen. Mean breath 13 C enrichment after drenching with NaCl was greater (P<0.001) than with water. Mean increases in enrichment after sucking molasses and label were greater than drenching with water (P<0.001) and NaCl (P<0.05). These results are consistent with sodium and sucking stimulating reticular groove contraction and support the use of this method as a simple, repeatable, non-radioactive and non-invasive means of detecting the route taken of orally administered therapeutic agents or nutrients. The test, for example, would identify those animals at risk by rumen bypass of anti-bloat agents.

The role of cysteine in the increased parasite susceptibility of Romney sheep selected for hogget fleece-weight. - Miller FM; Blair HT; Reynolds GW; Revell DK (Proceedings of the New Zealand Society of Animal Production, 1998)
To investigate the potential role of cysteine in the increased parasite susceptibility of sheep selected for increased wool production, ten sheep from both fleece-weight-selected (FW) and randomly-selected (C) Romney lines received either 2g of supplemental cysteine per day, or saline, via abomasal infusion. Following drenching to remove any pre-existing parasites, all sheep were dosed with Haemonchus contortus and Trichostrongylus colubriformis infective larvae. Cysteine infusion elevated plasma cysteine levels by an average of 65% (P<0.0001). Off-pasture faecal egg counts (FEC) were higher in FW than C sheep (645 versus 200 eggs/g, P<0.01). No significant effects of line or infusion treatment on FEC were observed following the trial infection, though on days 52, 57 and 58, FEC in sheep receiving saline were at least twice those of sheep receiving cysteine. Total H. contortus counts were greater in FW than C lines of sheep (1208 versus 1055, P<0.05), while total numbers of T. colubriformis did not differ between lines or infusions. This study confirms the greater susceptibility of FW sheep to internal parasites, and suggests cysteine may influence certain aspects of immunocompetency in sheep.

The role of milk production in dryland lamb production systems - Muir PD; Wallace GJ; McCall DG; Dodd CJ (Proceedings of the New Zealand Society of Animal Production, 1998)
A farmlet study was carried out over 2 years to examine the role of milk production in dryland lamb production systems. Poll Dorset and Romney ewes were used to represent high and low levels of milk production and mated to produce reciprocal cross lambs. High and low fecundity treatments were included in replicated farmlets of 2.9 ha and stocked at 15 ewes/ha. Mean lambing dates were 5th and 8th August with lambs drafted for slaughter from mid October. In Year 1, Poll Dorset ewes produced 44% (singles) and 88% (twins) more milk in peak lactation than their Romney counterparts. In late lactation, Poll Dorsets produced 41% (singles) and 169% (twins) more milk. In Year 2, the advantages were 19% (singles) and 18% (twins) in peak lactation and 78% (singles) and 67% (twins) in late lactation. Increased milk production had small effects on lamb growth rates in the low fecundity treatments (Year 1: 338 vs 328 g/d; Year 2: 317 vs 300 g/d for the respective high and low milk treatments). In the high fecundity farmlets, dam breed differences were larger (Year 1 :280 vs 244g/d ; Year 2: 307 vs 283 g/d, respectively). Number of lambs drafted by the 2nd December were also similar in low fecundity groups (Year 1: 93% vs 95%; Year 2: 90% vs 93%, respectively). Greater numbers of lambs were drafted off high fecundity Poll Dorsets than Romney dams (56% vs 23%) in Year 1 but not in Year 2 (85% vs 81%). The greater effect of milk on lamb growth in high fecundity treatments in Year 1 was attributed to poor spring feed conditions and the buffering ability of high milk producing ewes.

Ruminal utilisation of pasture nitrogen in response to increased level of dietary starch inclusion - Kolver ES; Muller LD; Varga GA (Proceedings of the New Zealand Society of Animal Production, 1998)
Four diets based on high quality pasture were formulated using additions of starch to contain 12.8, 19.6, 26.3, or 33% total nonstructural carbohydrate and were evaluated using four continuous culture fermenters during four 10 day periods. The true ruminal digestibility of organic matter was not changed by diet but the digestibility of neutral detergent fibre and crude protein linearly decreased, and the digestibility of total nonstructural carbohydrate linearly increased, as the level of starch inclusion increased. Production of NH3 N was reduced linearly from 35.2 to 14.2 mg/dl (P<0.001) and the flow of non-NH3 N as a proportion of total N flow increased linearly from 66% to 83% (P<0.001) as inclusion of starch increased. The quantity of microbial N and non-NH3 N flowing from continuous culture was unchanged. The experiment indicated that if the amount of organic matter digested is not appreciably increased by the inclusion of nonstructural carbohydrate then the linear increase in ruminal utilisation of pasture N arises more from a reduced pasture N intake than an improvement in microbial protein synthesis.

Sampling strategy for estimating dairy-pasture quality - Cosgrove GP; Betteridge K; Thomas VJ; Corson DC (Proceedings of the New Zealand Society of Animal Production, 1998)
Rapid determination of pasture quality using near infrared reflectance spectroscopy (NIRS) makes it feasible for farmers to incorporate forage composition in feed budgeting and feed supplementation decisions for grazing animals. In grazed pastures, heterogeneity in the distribution of the mass and quality, necessitates a sampling strategy to accurately predict the diet. A single paddock was systematically sampled by selecting 60 sites according to a pre-determined grid. At 12 of these sites, 4 separate but adjacent samples of 150 x 150 mm were taken from within a 300 x 300 mm quadrat. To characterise vertical heterogeneity, the herbage at each of the 60 sites was cut sequentially into 4 equal strata, the depth of each being one-quarter of the canopy surface height at that site. These samples were used to derive a statistically-based 3-dimensional characterisation of variability of herbage mass and of several parameters of herbage quality determined using NIRS. This description was used to calculate the number of samples necessary to estimate parameters to arbitary, pre-determined levels of accuracy of ± 50 kg DM/ha for herbage mass in each stratum, ± 50 g/kg protein (PROT), acid detergent and neutral detergent fibre (ADF; NDF), ± 20 g/kg for soluble carbohydrate (CARB), ± 25 g/kg for in-vitro dry matter digestibility (DIG) and ± 0.5 MJ/kg for metabolizable energy (ME). A minimum of six samples bulked together is necessary to estimate PROT, CARB, NDF and ADF to the specified level of accuracy, and this number was similar for each stratum. Twelve samples are required to estimate ME and DIG for each of the 3 upper strata, but in the lowest stratum with greater variability, 48 and 19 samples would be required for ME and DIG, respectively, to reach the same accuracy. A sampling strategy should take the suggested number of samples by systematically covering the paddock area. Uncertainty in the depth of sampling because of the necessity to sample before grazing has little effect on the number of samples required or on the accuracy of estimates, providing the lowest stratum is not penetrated during either sampling or grazing.

Seasonality of wool growth in Waikato and Southland of Romney sheep selected for high fleece weight - Sumner RMW; Wuliji T; Dobbie JL; Andrews RN; Upsdell MP (Proceedings of the New Zealand Society of Animal Production, 1998)
Wool growth rate was estimated for a total of 525 Romney ewes born in 1991 and 1992 between 5 and 28 months of age. Both year born groups contained sheep from three flocks selected over an extended period for increased hogget fleece weight and their respective Control flock. One flock was located in the Waikato, one in Southland and one split between the two locations. Following adjustment for live weight the seasonality of wool growth rate in Southland was significantly greater than in the Waikato reflecting the sensitivity of Romney sheep in recognising small changes in the length of daylight between the two locations. Selection for increased hogget fleece weight resulted in a greater increase in relative wool growth rate during the winter than during the summer.

Sheep breeding: an enterprise budgeting decision support model for on-farm planning. - Parker WJ; Dooley AE; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1998)
In selecting a sheep breeding strategy farmers need to evaluate the likely physical and financial outcomes relative to continuing the existing policy. The strategy should be assessed in terms of the new status quo production levels and costs and prices at this time, and the possible associated effect of changes in product attributes relative to market requirements. To assist farmers evaluate alternative breeding scenarios a spreadsheet-based enterprise budgeting model was developed. The input data and output are summarised to a one-page template to allow the user to assess the sensitivity of returns to different market and production scenarios for a particular farm situation. A flock at current performance levels and those in 5 years, following genetic and management improvement, is compared to a crossbreeding strategy to illustrate the model’s application.

A simplified method for typing DRB alleles in deer - Linscott EM; Mackintosh CM; Griffin JFT; Crawford AM (Proceedings of the New Zealand Society of Animal Production, 1998)
Major histocompatibility complex (MHC) genes present foreign antigens to the immune system and polymorphism in these genes may have a key role in the variability of the host response to pathogenic challenge. The DRB genes are part of the MHC class II family whose proteins present foreign antigenic peptides on the surface of the macrophage for recognition by the CD4+T cells of the immune response. The genes are highly variable with over 100 different variants found in some species. The goal of this study was the development and testing of a simplified system for differentiating between the different DRB alleles already identified in red deer. The typing method chosen used DNA hybridisation to discriminate between the DRB alleles. The RNA from each deer was extracted from cultured leukocytes. Reverse transcription followed by PCR was used to amplify the DRB region. Amino-linked oligonucleotides representing variable regions of the DRB region were covalently bound to a nylon membrane and probed with end-labelled PCR product. The degree of binding of the labelled PCR products to the membrane-bound oligonucleotides was used to discriminate between the different DRB genes amplified. This proved to be a simple and robust method of typing which eliminated any requirement for electrophoresis.

Some Effects of Using Progesterone and Gonadotrophin Releasing Hormone on the Reproductive Performance of Inseminated Cows - Taufa VK; Macmillan KL; Day AM; Ashcroft MJ; Morgan S (Proceedings of the New Zealand Society of Animal Production, 1998)
The administration of progesterone (P4) within 3 days following insemination can reduce pregnancy rates. In contrast, an injection of gonadotrophin releasing hormone (GnRH) at about 12 or 13 days after insemination can increase them by around 10%. This field trial tested the hypothesis that the negative effects reported for the P4 treatment on fertility could be eliminated by strategically injecting GnRH to convert the two ovarian follicle waves per cycle created by using P4, into three wave ones, with increased fertility. A total of 830 cows in 13 dairy herds received comparative treatments involving: (i) the insertion of a P4 intravaginal device 2 or 3 days after first insemination (1st insem.) for 10 days, with an injection of 10 mg of GnRH at device removal (P4 + GnRH); (ii) the same GnRH treatment but without P4 pre-treatment (GnRH); and, (iii) no post-insemination intervention (Control). Pregnancy status and conception date were confirmed by rectal palpation of uterine contents Calving data were recovered from 10 herds to monitor gestation length, dystocia and calf birth weight. The conception rates to 1st insem. were highest for the 255 cows treated with GnRH (64%; p = 0.05), but similar in the other two groups of 273 and 302 cows (57%). Second insemination results were not affected by the treatments; neither were final pregnancy rates. Birth weights were higher for bull than heifer calves (36.9 vs 33.0kg; p<0.01), but were not affected by treatment. The results of this trial showed that the P4 + GnRH treatment did have normal fertility and that GnRH injected 12 or 13 days after first insemination could increase conception rates.

Techniques for extraction of proteins for enzymatic measurements from ram spermatozoa and sheep muscle - Upreti GC; Oliver JE; Clarke AG; Clarke JN; Smith JF (Proceedings of the New Zealand Society of Animal Production, 1998)
A method for the preparation of enzyme active representative homogenates of muscle is described. This method was also valuated for spermatozoa and it was observed that the protocol needs to be adapted for various tissue types.

To shear or not to shear lambs? - Scobie DR; Bray AR; Cooper SM (Proceedings of the New Zealand Society of Animal Production, 1998)
Poll Dorset x Romney cross lambs (n = 80) were allocated according to sex (ewe, ram) and liveweight to either shorn or unshorn treatments. Pelts were recovered at slaughter, processed to dyed crust leather and scored for visual traits. At the pickled pelt stage, shorn lambs exhibited lower grain strain scores in the main panel (2.4 vs 4.3, P = 0.01). Rib score (2.3 vs 1.9, P = 0.014) was greater for shorn lambs. The fat score of ewe skins was higher (2.6 vs 1.9, P<0.001) and they produced thicker leathers (0.85 vs 0.79 mm, P = 0.025) with more delamination (2.6 vs 2.2, P = 0.004). While shearing risks scarring the pelt, there are trade-offs with other faults in the pelts of shorn or unshorn lambs. The decision on whether to shear lambs or not should be based on the relative costs of the faults.

Unravelling the causes of wool yellowing: Part I Involvement of a water soluble component - Winder L; Rea A; Scobie D; Bray A (Proceedings of the New Zealand Society of Animal Production, 1998)
The change in yellowness (D Y-Z) of wool samples maintained in an environment intended to stimulate yellow discolouration was determined in two experiments. In the first experiment, DY-Z was determined following one of six treatments - no extraction (control), solvent wax extraction (-W), aqueous suint extraction (-S), extraction of wax and suint (-WS), removal then reapplication of wax and suint (+WS), or detergent washing (D). Removal and reapplication of wax and suint, or removal of wax alone resulted in similar yellowing to the control (D Y-Z mean±SD); (control 1.6±1.2; +WS 1.5±2.8, p = 0.92; -W 2.1±1.3, p = 0.37). Detergent scouring, and removal of suint, or both wax and suint, reduced wool yellowing (D 0.6±2.2, p = 0.24; -S 0.5±1.6, p = 0.09; -WS 0.3±1.3, p = 0.04). In the second experiment, greasy wool from two chimaeric sheep producing both Lincoln and Merino wool types yellowed to a similar extent (Y-Z post challenge; mean±SD) (Lincoln 7.3±1.5; Merino 6.5±1.1; p = 0.45), suggesting that the fleece environment influences the propensity for yellow discolouration when distinct wool types are grown together. The data presented here support the hypothesis that a water soluble component of the fleece is involved in wool yellowing.

Unravelling the causes of wool yellowing: Part II Involvement of bacteria - Winder L; Baronian K; Webber J; Muller B (Proceedings of the New Zealand Society of Animal Production, 1998)
Wool was collected from five sheep with a propensity for wool yellowing. Sub-samples, from which the wool tip had been removed, were cut into 2cm lengths and incubated at 40°C for 6 days to provide an environment conducive to wool yellowing (YCT).Five treatments were applied to sub-samples of each fleece prior to YCT. Four sub-samples were gamma irradiated in an attempt to kill all bacteria present on the fleece (-B), the remaining subsample was not irradiated. Two -B sub-samples were re-inoculated with bacteria collected from the original fleece samples (+B). Each of the +B and -B samples was then either incubated at 0% humidity (-H) or 100% humidity (+H) for the YCT. Wool yellowness (Y-Z) was measured before and after YCT using standard methods. No relationship was apparent between the number of bacterial colonies in the original fleece (plated onto nutrient agar), and the pre-YCT Y-Z (R2=0.20; P=0.06), Y-Z after the YCT (R2=0.19; P=0.06), or the change in wool Y-Z during the YCT (R2=0.07; P=0.27). Gamma irradiation eliminated bacteria from the wool samples but increased their Y-Z pre-YCT (mean ± S.D, non-irradiated 2.46±0.55; irradiated 4.35±0.43; P<0.001). Discolouration of wool (Y-Z) was increased by humidity during YCT (-H 1.06±0.45, +H 4.96±1.46; P<0.001). At 100% humidity, reinoculation with bacteria increased wool Y-Z during YCT (+B 6.13±0.87; -B 3.78±0.75; P<0.01). This effect of reinoculation was lost at 0% humidity. The interaction between humidity and reinoculation was significant (P<0.05). This study supports the hypothesis that bacteria are involved in the yellow discolouration of wool in the presence of high humidity.

Use of 'Barkant' turnips and 'Superchow' sorghum crops to increase summer-autumn milk production - Harris SL; Clark DA; Waugh CD; Copeman PJA; Napper AR (Proceedings of the New Zealand Society of Animal Production, 1998)
`Barkant` turnips and `Superchow` sorghum were compared as summer-autumn crops for lactating cows. Crops were fed at three levels (0, 4 and 8 kg DM/cow/d) to supplement pasture offered at a constant allowance. Sixty twin cows were used in two experimental periods in February and March 1997. Feeding 4 or 8 kg DM/cow/day increased milksolids (MS) yield/cow by 29% or 36% for turnips, and 26% or 32% for sorghum compared with pasture alone. Turnips gave responses of 58g and 45g MS/kg DM offered, at the lower allowance, in summer and autumn respectively, compared with 45g MS/kg DM in both seasons for sorghum. For both crops, increasing allowance from 4 to 8 kg further increased MS yield. Crop utilisation was lower on sorghum than turnips but substitution rates for turnips were higher than for sorghum at both allowances in both summer and autumn. This means that although both crops have a `pasture sparing` effect, sorghum contributed more to increased per cow intake.

Use of once daily milking compared with treatment with progesterone and oestradiol benzoate (ODB) in anoestrous cows - Rhodes FM; Clark BA; Macmillan KL; McDougall S (Proceedings of the New Zealand Society of Animal Production, 1998)
The aim of this study was to compare the rate of resumption of oestrous cycles and fertility to first insemination of anoestrous cows examined 7 days before the planned start of mating (PSM), which were milked once (OAD) or twice daily (TAD) for at least 28 days and untreated or treated with progesterone and oestradiol benzoate (ODB; CIDR). By 28 days after the start of treatment, oestrus was detected in 65.8%, 76.6%, 93.5% and 97.9% of cows (TAD, OAD, TAD+CIDR and OAD+CIDR, respectively) (p<0.001). Conception rates to first insemination were lower in CIDR treated than untreated cows (40.4% vs 50.3%; p<0.05), but were not affected by milking frequency. The mean (± sem) interval from PSM to conception was shorter in CIDR treated than untreated cows (12.8 ± 1.2 vs 19.0 ± 1.3 days; p<0.001). Daily milk yield decreased by 6.1 ± 0.2 and 2.2 ± 0.2 litres; and milk solids by 0.46 ± 0.02 and 0.19 ± 0.02 kg (p<0.001) in cows milked OAD and TAD, respectively, over the treatment period. Once daily milking increased the rate of spontaneous resumption of oestrous cycles in anoestrous cows compared with TAD, but was associated with a significant decrease in milk production. Compared to treatment with progesterone and ODB, OAD resulted in a longer interval from PSM to conception.

Using nitrogen fertiliser to increase dairy farm profitability - McGrath JM; Penno JW; MacDonald KA; Carter WA (Proceedings of the New Zealand Society of Animal Production, 1998)
Five farmlets were established to investigate the profitability of using nitrogen fertiliser (N) to increase pasture supply and milksolids production. Farmlets were stocked with 3.34 (low) or 4.42 (high) Friesian cows/ha and received 0, 200 or 400 kg N/ha/year. Total annual pasture production was increased by 1.76 and 0.97 t DM/ha when 200 kg N/ha was applied and by 3.2 and 3.6 t DM/ha using 400 kg N/ha at the low and high stocking rate, respectively. Annual milksolids production increased by 142 and 218 kg MS/ha after the application of 200 and 400 kg N/ha, respectively. Increasing stocking rate from 3.34 to 4.42 cows/ha reduced milksolids production by 99 kg MS/cow. Applying 200 kg N/ha at the lower stocking rate increased economic farm surplus by $148/ha. Increasing stocking rate reduced total milksolids production and profitability at both rates of N.

The value of monozygotic twins in milk composition experiments. - Auldist MJ; Mackle TR; Hooper RJ; Henderson HV (Proceedings of the New Zealand Society of Animal Production, 1998)
Monozygotic (identical) twins have for many years been used to increase the statistical power of experiments in a range of scientific disciplines (Dick and Whittle,1951). In dairy cows, variation within identical twinsets for a given biological parameter is usually substantially less than the variation between unrelated cows or between fraternal twinsets (Hancock 1953; Brumby and Hancock, 1956). Thus the number of identical twins required in an experiment is often considerably less than the number of unrelated cows necessary to achieve the same statistical precision. The experiments described here were conducted to quantify the twin efficiency values of a range of milk composition parameters.

Variation in copper metabolism between two flocks of Romney sheep in response to increasing dietary intake of copper - Knowles SO; Rounce JR; Grace ND; Lee J (Proceedings of the New Zealand Society of Animal Production, 1998)
Differences in the Cu status of two flocks of Romney lambs were observed which suggest that lines of sheep having distinct Cu metabolism have been identified. As part of a larger study relating Cu intake to Cu status of grazing lambs, changes in concentrations of Cu in liver, plasma and other tissues, and in erythrocyte Cu/Zn superoxide dismutase (SOD) were monitored for 176 days in two flocks of 50 sheep. The animals grazed on ten experimental paddocks treated with 0, 0.4 or 4 kg Cu/ha which resulted in mean pasture herbage Cu concentrations of 8 (Control), 13 (Low), and 41 (High) mg Cu/kg DM. At the start of the experiment these lambs, sourced from two Wairoa farms, had markedly different liver Cu reserves (1270 v 190 mmol Cu/kg FW, flocks H and L respectively) which could not be attributed to Cu supplementation. This difference between flocks was maintained throughout the 176 day study for sheep grazed on control pastures, through day 99 for sheep on the low pastures, and for 51 days in sheep on the high paddocks. High copper intakes increased liver Cu concentrations to as much as 4800 mmol (300 mg) Cu/kg liver FW after 99 days, with no signs of chronic Cu toxicity. Initial flock differences in liver Mo concentration (14.7 v 20.6 mmol Mo/kg FW, n=10, P<0.05) disappeared by day 51. The first measured SOD activity (day 51) in flock H was 17% greater than that of flock L (1600 v 1370 U/g Hb, n=21, P<0.01) and this flock difference was maintained through day 142 and day 99 for sheep grazing control and low pastures, respectively. SOD activity was found to be a reasonable predictor of liver Cu stores only in sheep having low to moderate Cu intake. Had the differences in initial liver Cu concentration and in blood Cu/Zn SOD activity of the two flocks been merely a reflection of the Cu and Mo status of their respective Wairoa farms, the disparity would have been expected to diminish much more quickly than was observed in this study. Factors controlling Cu metabolism are heritable. Trials selecting for differences between flocks in liver Cu concentration are needed to establish whether these flocks are genetically distinct in the way they metabolise Cu.

Variation in milk whey composition throughout lactation in cows of different Beta-lactoglobulin phenotypes. - Turner S-A; Auldist MJ; Molan PC; Prosser CG (Proceedings of the New Zealand Society of Animal Production, 1998)
The association between b-lactoglobulin (β-LG) variants and milk composition throughout lactation was determined by sampling from 44 Friesian cows (22 homozygous for b-LG AA and 22 homozygous for b-LG BB) in early (day 6 postpartum), established (1-3 months postpartum) and late lactation (on the day of drying off). Results indicated that differences between β-LG AA and BB phenotype milk (expressed as a percentage of the level in phenotype AA) in concentrations of bovine serum albumin (BSA; -15.9%, -32.0%, -42.5%) and b-LG (5.9%, 16.0%, 32.2%), in early, established and late lactation respectively, increased steadily as lactation progressed. The differences in a-lactalbumin concentrations were less variable (1.2%, -9.0%, -9.1%). These results provide new evidence that compositional differences are not seen between b-LG AA and BB phenotype milk until established lactation.

Wool fibre diameter effects on yarn bulk independent of core bulk - Maddever D; Bray A (Proceedings of the New Zealand Society of Animal Production, 1998)
The curvature and diameter of fibres influence the core bulk of raw wool, which in turn is used as an indicator of yarn bulk. The compressional properties of fibre masses are difficult to predict from first principles, therefore the direct effect of fibre diameter and curvature on the bulk of semi-worsted yarn was investigated. Wools with similar core bulk (28 cm³/g) in which fibre diameter ranged from 18.5 to 40 mm were processed into semi-worsted yarn and measured for yarn bulk. Contrary to popular belief, fine wool of the same core bulk produced yarn with higher bulk than stronger wool. However, with a correlation coefficient of -0.9 between mean fibre diameter and mean fibre curvature the influence of these two attributes on yarn bulk cannot be separated. Closer examination of the data shows that for these wools, which were selected to have constant core bulk, the variation in yarn bulk can be predicted slightly more accurately by the variation in mean diameter than the variation in mean fibre curvature between the samples. Rather low R² values and the size of the coefficients in the regression equations indicate that the influence either fibre diameter or fibre curvature has on yarn bulk at 28 cm³/g core bulk is small. Wool type also had little effect on the relationship between core bulk and yarn bulk at this level of core bulk.

Wool follicle traits of half Merino half Romney F1 , and backcross three-quarters Merino quarter Romney gene mapping flocks - Andrews RN; Beattie AE; Dodds KG; Wuliji T; Montgomery GW (Proceedings of the New Zealand Society of Animal Production, 1998)
Wool follicle traits and mean fibre diameter (MFD) of ½ Merino ½ Romney F¹ (MR), and ¾ Merino ¼ Romney backcross (MRM) were compared. Skin and midside samples were collected from 25 ewes and rams of MR and 420 MRM progeny. MRM was lower than MR for MFD by 3.0 mm, follicle fibre area (FFA) by 162.4 mm², and diameter (FFD) by 4.1 mm, but greater for total follicle density (DEN) by 21.7 mm-2 , primary density (PD) by 0.8 mm-2 , and secondary to primary ratio (SPR) by 4.8 units. Most traits had significant differences (P<0.05) for birth year, breed and sire group, but only PD and SPR were significant for sex and birth/rearing rank. FFD was positively correlated (P<0.001) with MFD (r = 0.22), and the relationship had a common slope of 0.7, but intercepts were significantly different (P<0.01) across birth years (i.e. 13.5, 12.0, and 10.9 mm for born 1991, 1992, and 1993).

Accumulation of cadmium in kidney and liver tissue in the suckling Romney lamb from parturition to early weaning. - Rounce JR; Grace ND; Lee JL (Proceedings of the New Zealand Society of Animal Production, 1997)
In earlier work we investigated the accumulation of cadmium (Cd) in the developing foetus and compared the movement of Cd with that of zinc (Zn) into the liver and kidney. Concentrations of Cd in foetal tissue were ex-tremely low, although there was a small flux across the placenta at about 100d of development concomitant with that for Zn. There was no relationship of foetal Cd with the Cd status of the mother. It was only after parturition that Cd concentrations in liver and kidney started to increase (Rounce et al.,1995). We also showed that the rate of Cd accumulation in weaned animals was greatest at an early age when growth rates were also at or near their peak (Lee et al.,1996). The aim of this study was to define Cd accumulation in tissues of Romney neonates, as affected by relative Cd concentrations in pasture and milk from partu-rition to weaning.

Across-breed genetic evaluation of New Zealand dairy goats. - Singireddy SR; Lopez-Villalobos N; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1997)
The New Zealand dairy goat industry consists of 187 herds (33,500 does), from which 60 herds (12,600 does) supply milk for the Dairy Goat Co-operative. Most of the milk is used to manufacture whole milk powder for niche markets. Farm profitability can be increased through identifying and selecting superior animals for traits of financial importance such as milk yield. Across-breed estimated breeding values (EBVs) for milk yield adjusted for days in milk (MYA), unadjusted milk yield (MYU) and days in milk (DIM) of Saanen, Nubian, British, Toggenburg and crossbred dairy goats spread across 20 herds were estimated by Best Linear Unbiased Prediction (BLUP) procedures. A repeatability model was used to analyse the first eight lactation yields and included effects of herd-year-month, parity, additive genetic and permanent environment. Coefficients of breed composition and heterosis (assuming equal heterosis among any of the breeds) and days in milk were considered as covariables. Heritability and repeatability were 0.36 and 0.63 respectively. Evaluations were based on 6,517 lactation records of 3,856 does and 83 sires. Average milk production was 548 litres over an average lactation spanning 200 days. Pure-bred Saanen does had longer lactations (DIM) and out-produced other breeds in MYA and MYU. Two year old does produced an extra 150 litres of milk compared to one year old does. Peak production was at 5 years of age then production declined gradually. Young does had longer lactations than old does. Average EBVs for different breeds compared to a Saanen base were for MYU Nubian -291, British -242 and Toggenburg -106 litres, MYA -177, -193 and -51 litres and DIM -40, -17 and -19 days for each breed respectively. First cross heterosis was 105 litres (19%) for MYU, 52 litres (9.5%) for MYA and 18 days (9%) for DIM. This first prototype evaluation allows the selection of does and bucks based on their estimated genetic merit and provides for routine genetic evaluation in the future.

Age at castration after puberty has no effect on carcass weight. - Cosgrove GP; Knight TW; Death AF; Lambert MG (Proceedings of the New Zealand Society of Animal Production, 1997)
Bulls grow faster than steers but produce meat with lower quality, which presents fewer marketing opportuni-ties. Castration post-puberty improves several attributes of meat quality compared with bulls and theoretically it could be used to exploit the faster growth rates of bulls. How-ever, the 23 kg liveweight advantage of bulls over steers, when surgically castrated at 17 months-of-age, was lost in the subsequent 5 months to slaughter, because of poorer post-castration growth rate (Cosgrove et al.1996). It was not clear whether this was because of stress from surgical castration, or physiological effects associated with their age at castration. This trial examined the effect of age at castration on subsequent growth rate and carcass character-istics at slaughter.

Agricultural ethics - a role in animal production? - Fisher MW (Proceedings of the New Zealand Society of Animal Production, 1997)
Science and farming benefit society in innumerable ways, but like other human activities, are subject to value judgements of what is and is not acceptable. In addition to traditional measures of efficiency and profitability, the acceptability of agricultural practices is also determined by requirements of food safety, resource use, environmental and animal welfare criteria, and by social and philosophical views. Since moral issues may be difficult to deal with, and are determined by a wide array of influences ranging from philosophers to the media, it is important that we establish a means of clarifying them. Agricultural ethics provides such a common framework or language. This includes tradition and common sense (our common morality), and consideration of the rights of individuals and of the consequences of our actions. In addition, the role that virtues and myths play in determining the acceptability of agricultural practices can be incorporated.

Is beef with yellow fat healthier for you than beef with white fat? - Knight TW; Death AF (Proceedings of the New Zealand Society of Animal Production, 1997)
Fat samples were collected from 20 Angus grass fed steers 24 hours after slaughter. Fat colour was measured with a Chromameter (b* values) and the carotenoid concentration and fatty acid (FA) composition of the fat were analysed. Carotenoid concentration in the fat was low (1.54 ± 0.11 mg/g fat) compared to that found in vegetables. As b* values, and therefore the yellowness of the fat increased the proportion of saturated FA decreased (r = -0.58; P<0.001) and mono-unsaturated FA increased (r = 0.68; P<0.0001). The relationship was not as strong for carotenoid concentration even though the correlation between carotenoid concentration and b* values was high (r - 0.86; P<0.001). The conclusions were that the potential health advantages of beef with yellow fat compared to beef with white fat were small, especially as the relationships appeared to only apply within a herd.

Behavioural of dairy heifers during adaptation to milking - Bremner KJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Effects of prior handling on behaviour of heifers at milking was studied in 42 Friesian heifers (reared on nurse cows, Herd A) and 36 monozygotic twins (calfeteria-reared, Herd B). Herd A heifers were allocated to 3 treatments: No Handling (N) - no handling or parlour experience; Limited Handling (L) - moved through the parlour during two sessions; or Familiarised (F) - 14 sessions during which animals were tamed, moved through the parlour and handled around the udder. Herd B heifers were allocated to N or F only. Behaviour at various stages of milking was observed during the first 14 milkings. Despite significant variation between individuals, all Herd A heifers significantly decreased moves and kicks from Period 1 (milkings 1 - 7) to Period 2 (milkings 8 - 14), and improved milk letdown but treatments were not significantly different at the various stages of milkings. However in Herd B, pre-milking handling and experience of the milking environment consistently reduced the frequency of adverse responses by heifers at most stages of milking.

Brief Communication: Increased litter size elicits cell proliferation in the lactating murine mammary gland - Auldist D; McFadden T; MacKenzie DDS; Nicholas K (Proceedings of the New Zealand Society of Animal Production, 1997)
Milk quality of dairy cows decreases both as lactation progresses and as milk yield declines (Lucey, 1996). De-clining milk yield has been associated with a diminishing population of secretory epithelial cells (Knight and Wilde, 1993). One approach to enhancing the persistency of lactation is to stimulate a wave of proliferation of epithelial cells within the gland. A new generation of epithelial cells could increase milk yield and might also improve the overall quality of the milk.

Brief Communication: Seasonal and lactational influences on milk composition in New Zealand - Auldist MJ; Walsh BJ; Thomson NA (Proceedings of the New Zealand Society of Animal Production, 1997)
In New Zealand, seasonal calving has created marked variations in the volume and composition of milk supplied to processors across the season. As a consequence, there are also seasonal variations in the manufacturing properties of the milk (Kefford et al.1995). In particular, milk from later in the season can have manufacturing properties which are different from those of early and mid-season milk. Milk from this time typically has elevated concentrations of blood proteins, low casein:whey ratios and an altered min-eral balance (Lucey, 1996). The 2 major factors attributed to causing this phenomenon are the stage of lactation (SOL) of the cows, and seasonal influences which affect both pasture and cows. In a seasonally-calving dairy sys-tem, the precise contributions of these factors to the re-ported changes in milk composition are difficult to define because of the confounding influences of other factors. The aim of the investigation presented here was to separate the respective effects of season and SOL on milk composition.

Bulk and fibre diameter affect leather and woolskin quality of lamb skins - Scobie DR; Cooper SM; Passman A; Young SR (Proceedings of the New Zealand Society of Animal Production, 1997)
Poll Dorset x Romney lambs were chosen from a group of 300 on the basis of measured diameter and bulk. The selected lambs made up four groups of twenty, that had the four possible combinations of low (LD) or high diameter (HD) (29 or 32 um), and low (LB) or high bulk (HB) (22 or 26 cm³/g). Pelts were recovered at slaughter, assessed for woolskin tanning, processed to dyed crust leather and scored for the grain surface defect known as pinhole (1 to 5, best to worst). Suitability for woolskins was greatest for the high bulk groups (LDHB, 20; HDHB, 18), and least for the HDLB group (5), with the LDLB group intermediate (13). More pelts were found to exhibit pinhole in the high bulk groups (HDHB, 16; LDHB, 16 vs HDLB, 8; LDLB,10) and mean pinhole scores were higher (p <0.001) for these groups (HDHB, 2.5; LDHB, 2.4, vs LDLB, 1.7; HDLB, 1.5). Woolskins are a more appropriate product for finer and bulkier wool types, whereas less bulky wools of high diameter lend themselves to leather production, because they are unsuitable for woolskins and less prone to pinhole.

Can protein utilisation from pasture be improved? - Ulyatt MJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Although temperature pasture plants usually contain sufficient protein to potentially support most types of animal production, this protein is utilised for ruminant production with relatively low efficiency because of the losses that occur via microbial deamination in the rumen. These processes are well understood, yet procedures that should theoretically improve protein capture, such as the addition of soluble carbohydrate or protected protein to the diet, are frequently not effective. The paper considers reasons for this situation. It also examines several additional reasons why plant protein utilisation may be impaired, such as high rumen degradability, hepatic detoxification of absorbed ammonia and its associated costs in terms of amino acid catabolism, and the relationship between amino acid supply to the duodenum and tissue amino acid requirements. The paper evaluates whether an enhanced supply of individual amino acids, or mixtures of amino acids, to the tissues might increase the production of meat, milk and wool. It also considers whether we have enough information to be able to assess the likelihood of using specific enhanced amino acid supply or novel combinations to manipulate product quality. The efficacy of various mathematical models of protein digestion and metabolism are evaluated in relation to our current knowledge of the subject.

A candidate gene approach to animal quality traits. - Palmer BR; Hickford JGH; Bickerstaffe R (Proceedings of the New Zealand Society of Animal Production, 1997)
A variety of animal quality traits, particularly those associated with meat and wool production and disease resistance, have been the subject of sophisticated genetic analyses. Investigation of the biochemistry and physiology underlying disease or production traits has implicated particular proteins and hence genes as "candidates" for having major phenotypic effects. This makes the candidate gene approach a useful complement to animal genome mapping of markers and QTLs. We have applied the candidate gene approach for the sheep quality traits of meat tenderness and footrot resistance. A three allele system detected by polymerase chain reaction - single strand conformational polymorphism (PCR-SSCP) has been observed for the ovine calpastatin gene. Calpastatin is the specific inhibitor of the ubiquitous calcium-dependent proteases u-calpain and m-calpain. There is very strong population genetic and protein assay data in cattle to inversely correlate post-mortem calpastatin levels with meat tenderness. Assay of post-mortem calpastatin levels in aging lamb confirms an important regulatory role for calpastatin in sheep meat aging. Data sets from preliminary experiments testing the association of the three allele ovine calpastatin system with meat tenderness values and other meat quality characteristics show significantly different fillet tenderness, early post-mortem calpastatin and u-calpain levels between ewes with different calpastatin genotypes. The early post-mortem calpastatin levels and the longissimus dorsi pH at 24 hr post-mortem of sheep representing two different genotypes was also significantly different. The major histocompatibility (MHC) proteins of vertebrates have a role in presenting peptide fragments from pathogenic organisms to the systemic immune system. It is hypothesised that a component of resistance in sheep to footrot is based on an effective systemic immune response and hence controlled by MHC presentation. Sixteen alleles have been identified at the ovine MHC class II DQA2 locus and 8 at the DQA1 locus. A significant (p=0.001) association between footrot status and DQA2 genotype was observed in a halfsib family challenged with the disease under standardised field conditions.

Cattle diet preference and species selection as influenced by availability. - Torres-Rodriguez A; Cosgrove GP; Hodgson J; Anderson CB (Proceedings of the New Zealand Society of Animal Production, 1997)
Diet composition is partly determined by selective grazing. In general, cattle show a preference for a mixed diet (Cosgrove et al., 1996), with partial preference for legumes over grasses (Parsons et al., 1994). This work was conducted to determine if cattle modify their dietary pref-erence as the availability of a preferred species decreases.

Changes in fibre and follicle characteristics related to wool bulk during the lifetime of Perendale ewes. - Sumner RMW; Dick JL (Proceedings of the New Zealand Society of Animal Production, 1997)
Wool and skin samples were collected annually at hogget shearing in October and thereafter in July for a further four shearings, from a total of 32 Perendale ewes born in 1990 and 1991 within lines selected for or against wool bulk. Time to form a crimp, follicle curvature and the proportion of para-meso cortical cells, increased towards an asymptote with increasing age. Proportion of fibres with a bilateral arrangement of cortical cells was maximal at 2 years of age and clean fleece weight, staple length and fibre diameter were maximal at 3 years of age. Fibre curvature decreased linearly, crimp frequency and follicle length decreased curvilinearly but wool bulk did not change with increasing age. The repeatability of individual characteristics decreased with increasing age. There was no significant difference in the relationship between core bulk and a combination of fibre curvature, fibre diameter and fibre diameter variation within each age group.

Changes in the activities of plasma membrane bound sperm enzymes during semen processing. - Oliver JE; Upreti GC; Duganzich DM; Smith JF (Proceedings of the New Zealand Society of Animal Production, 1997)
The physico-chemical changes in spermatozoa that take place during semen processing and storage regulate the fertilising ability of spermatozoa. Spermatozoa1 motil-ity, traditionally used as a marker of fertilising ability, does not indicate the true fertilising ability of spermatozoa (Smithet al., 1993),although motility is required for in vivo fertilisation. In this study we have monitored changes in activities of spermatozoa1 enzymes at various stages of semen processing. In future, these changes could be corre-lated to fertilising ability. It is also anticipated, that the information on these enzymes would improve our under-standing of basic sperm physiology.

Characterisation of muscle development in double muscled and normal bovine fetuses. - Martyn JAK; Oldham JM; Berry CJ; Kirk SP; McGarry BC; McMillan WM; Bass JJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Double-muscled (DM) cattle have increased numbers of muscle fibres and most muscles are heavier, although certain muscles are reduced in weight relative to non-double-muscled animals. This study was undertaken to investigate whether this differential muscle growth seen in the adult was apparent during foetal growth. Foetuses with presumptive DM phenotype were compared to presumptive non-double-muscled controls (NDM), at four gestational ages. Body weight (p</=0.001), but not crown rump length was greater in DM foetuses. Both the M. vastus lateralis and the M. vastus medialis were heavier in the DM (p0.001). In DM there were fewer type 1 fibres per fascicle in both muscles (p</=0.001), and M. vastus lateralis, at 210 and 260 days, had smaller type 1 fibre areas (p</=0.001). In conclusion, our data demonstrate differences in muscle development between DM and NDM foetuses, and suggest that the relatively reduced size of M. vastus medialis in the DM adult, is attained postnatally.

Classing Merino fleeces into uniform lines with predicted adult fibre diameters. - Andrews RN; Land JTJ; Dodds KG; Wuliji T (Proceedings of the New Zealand Society of Animal Production, 1997)
The effectiveness of 3 wool classing methods, to separate fleeces into uniform lines of different mean fibre diameter (MFD) and to maximise net financial returns were compared. The methods were predictive (i.e. uses hogget MFD), objective (i.e. adult MFD) and subjective (i.e. visual). A flock of mixed-age Merino ewes, (n = 2,640; adult MFD = 19.9 ± SD 1.3 um) were randomly drafted into predictive, objective and subjective groups for midside sampling and measurement of adult MFD pre-shearing. Predicted MFD was calculated from the correlation of hogget with adult MFD. MFD of grab-samples of lines were, predictive 20.0 um, objective 20.1 um, and subjective 19.9 um. The % CV of fibre diameter of grab-samples of objective lines was 0.4 and 0.9 less than predictive and subjective respectively. For a range of prices, premiums for the fine edge of the clip were generally insufficient to cover objective measurement costs.

Comparison of weight-selected Romney hoggets for growth and ultrasonic fat and eye muscle dimensions. - Clarke JN; Dobbie JL; Jones KR; Uljee AE; Wrigglesworth AL (Proceedings of the New Zealand Society of Animal Production, 1997)
Lines of Romney sheep selected for either weaning (WWW) or yearling body weight (TYW and HYW) for 25 years were compared relative to their respective controls in a common environment using two unselected crops of male and female progeny. The weaning weight (WWW) line and one of the yearling weight (TYW) lines were derived from a common base flock, of diverse origin. The WWW line maintained a similar body weight advantage of approximately 20% over its control at 5, 8, 10 and 14 months of age. All control lines showed very similar average body weight trends with age (28.0±0.5, 33.9±0.05, 35.3±0.06 and 42.6±0.7). In contrast the yearling weight lines showed increasing divergence with age from 22% in February to 28% (TYW) and 31% (HYW) at 13 months. All lines, and especially the yearling weight lines showed some weight increase over the winter (May to July). Eye muscle depth and width changed little over the winter compared with the previous autumn or the following spring, in contrast to fat depth trends which increased in all lines but for which however, there was little line divergence among the yearling weight lines during the winter. All selected lines had significantly lower eye muscle dimensions at the same liveweight than their controls (by 4% for width and 5% for depth). Lines also showed contrasting divergence in average weight-adjusted fat depth relative to their controls, especially those derived from the same base population. As judged by reductions in subcutaneous fat depth, the WWW line lost its initial leanness superiority (4% lower fat depth) during the winter, the TYW line increasing its superiority (16-17% lower fat depth) during the winter and spring. The other yearling liveweight line (HYW) showed only half the leanness superiority over its control at these times. Thus, lines selected for improved growth alone had different patterns of muscle and especially subcutaneous fat development in a desirable direction for commercial lean lamb production, but responses were variable.

Contract Summary - Fennessy PF (Proceedings of the New Zealand Society of Animal Production, 1997)
This set of papers illustrates superbly the very rapid developments indissecting the underlying genetics behind the phenotype we see. The progress is not only in gene mapping itself but in the development of the powerful analytical tools, both at the conceptual (e.g. FINDGENE) and at the software level. The progress in developing gene maps in livestock is built on the back of the Human Genome programme with the rapid developments in laboratory and statistical tech- niques. The general conservation of genome organisation across widely divergent species is itself a huge advantage in constructing new maps. In this respect, the deer hybrids are proving a remarkable raource and may well prove to be an ideal ruminant prototype map on which to map new markers.

Control of Reproductive Success in Rabbits Using Bromocriptine. - Cottam YH; Peterson SW; McCutcheon SN (Proceedings of the New Zealand Society of Animal Production, 1997)
Feral rabbits impose a substantial environmental and economic cost in this country, causing pasture devastation over large areas of land, accelerating erosion and decreasing vegetation cover. Existing or potential methods of control have a high ethical cost, and there is a need to identify new methods of control. Manipulation of lactation, to enhance mortality and inhibit growth and development of the young, is a possible alternative strategy. Prolactin (PRL) is known to be important for establishment and maintenance of lactation in rabbits, and PRL secretion may be inhibited by administration of ergot alkaloids such as bromocriptine (CB154). These substances are orally active and so could potentially be used in baits. In order to determine whether CB154 could be used in baits, it is first necessary to establish the lowest effective dose. The objective of this study was to examine the relationships between dose of CB154 (initially administered systemically) and the growth and survival of kits. Sixteen pregnant New Zealand White does were divided into four treatment groups receiving different doses (mg/kg live weight/d) of CB154 ("low"(L), 0.2; "medium"(M), 0.4; "high"(H), 0.8; and control (C), 0). From day 3 of lactation, does were injected once daily with CB154 or excipient. Treatment continued until day 14 or until the death of all the kits, whichever came first. There were significant treatment effects on the proportion of kit deaths on all measurement days. By day 17, kit mortalities were: C, 20%; L 42%; M, 64%; H, 71%;) (P<0.05). The weight gain of the surviving kits from day 3 to 8 did not differ significantly between treatment groups, but kit weight gain day from days 8 to 13 showed a significant treatment effect (P<0.01) (control, 83.7±11.4g; low, 18.7±11.4g; medium, 33.5±17.2g; high -0.8±14.9g). Results are discussed in relation to the possible use of bromocriptine as a bait to control reproductive success, and to the fact that these rabbits were much less sensitive to bromocriptine than previously published studies would suggest.

Correlated responses in fleece weight to selection for high or low faecal egg count in New Zealand Romneys and Perendales. - Morris CA; Bisset SA; Baker RL; Watson TG; Wheeler M (Proceedings of the New Zealand Society of Animal Production, 1997)
Three selection experiments, two involving Romneys (at Wallaceville and Ruakura) and the third involving Perendales (at Ruakura), have resulted in breeding lines showing significant divergence in faecal nematode egg count (FEC), under natural challenge. The High and Low FEC lines in each experiment experienced 18, 8 and 11 years of selective breeding respectively to 1996. The geometric means of FEC in the three experiments were 7.3, 2.0 and 4.5 times greater in the High than the Low lines, equivalent to divergences of 2.12, 0.80 and 1.27 phenotypic standard deviations. In the present analysis, the High and Low lines were compared for greasy fleece weights using both yearlings (YFW) and mixed-age ewes (EFW). Relative to the Low lines, the corresponding High lines had greater YFWs by 14.6±3.0, 7.9±2.4 and 5.3±3.1% respectively (mean of three, 9.1±1.6%), and they had greater EFWs by 14.9±1.7, -3.2±3.8 and 8.0±2.7% (mean of three, 10.9±1.3%). The conclusion is that single-trait selection for reduced FEC in Romneys and Perendales is associated with reduced greasy fleece weight, when they and less resistant animals graze together.

Cost-benefit analysis of ultrasound scanning in meat breed ram breeding flocks. - Binnie DB; Clarke JN; Rae AL (Proceedings of the New Zealand Society of Animal Production, 1997)
New software, able to account for the impact of early selection on genetic variances and covariances, was used to evaluate two-stage sequential selection schemes for genetic gains in terminal sire flocks. The objective was to increase carcass lean and decrease carcass fat. Ultrasound scanning of both ram and ewe replacements was financially rewarding. There was little difference between autumn and spring scanning for rams. Ultrasound scanning was significantly more rewarding in the South Island Intensive situation than the North Island Hard Hill Country. The scale of rewards varied significantly with generation interval in the ram breeding flocks.

Effect of breed and diet on de novo synthesis of fatty acids by mammary gland tissue of Friesian and Jersey dairy cows. - van den Koedijk CDMA; Thomson NA; McFadden TB (Proceedings of the New Zealand Society of Animal Production, 1997)
Differences exist in the fatty acid (FA) composition of milkfat of Jersey and Friesian cows. Milkfat triglycerides are produced in mammary epithelial cells using FAs taken up from circulation as well as FAs synthesised de novoby the gland. The aim of the present experiments was to determine whether mammary metabolism is responsible for milkfat differences between breeds and to determine effects of diet on these.

Effect of crossbreeding strategies on long-term rates of genetic gain in New Zealand dairy cattle. - Lopez-Villalobos N; Garrick DJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Crossbred cows tend to be more profitable than straightbred cows because they fit the present milk payment system and show favourable heterosis for milk traits. This may encourage greater use of crossbred cows eroding the number of potential bull mothers (active cows) thereby reducing genetic progress. The objective of this research was to evaluate the effects of crossbreeding on active cow numbers and genetic gain over 25 years. A deterministic model was used to calculate the number of cows and the breeding worth (BW) of Holstein-Friesian (F) and Jersey (J) bulls each year. Three strategies were considered: upgrading to F (UPGF); upgrading to J (UPGJ); and some two-breed rotational mating plans. In 1996, sizes of F and J active populations were taken to be 250,000 and 76,400 cows and mean bull BWs were $72 (F) and $82 (J). After 25 years of UPGF the number of active F and J cows were 1,520,000 and 13,000, the BWs of F and J bulls were $245 and $213 and genetic gains of F and J bull teams were 8.5 and 4.25 $BW/year. UPGJ had the opposite effect. Mating 10% of •2/3F cows to F bulls and 10% of 1/3F cows to J bulls (ROTATE10) for 25 years led to active F and J populations of 70,200 and 75,800 cows, BWs of F and J bulls of $227 and $230 and genetic gains for F and J bull teams equal to 7.0 $BW/year. Results suggest that widespread adoption of a rotational crossbreeding scheme could be achieved without penalising annual genetic gain in bulls. However, annual recruitment of new active cows should be routinely monitored to ensure long term gain will be maintained.

Effect of different ivermectin topical solution treatment regimens on weight gain in beef weaners. - Webster MC; McPherson WB; Bowie JY; Ryan WG; Gross SJ (Proceedings of the New Zealand Society of Animal Production, 1997)
Four trials were conducted in separate geographic regions in New Zealand, using a total of 483 cattle to compare different treatment regimes with topical ivermectin in weaned beef calves. Trial cattle received topical ivermectin at 500ug/kg liveweight once (control group), four times (4x) or six times (6x) at six-weekly intervals commencing at weaning (March/April) and continuing into early or late summer (November/February). Cattle were weighed at intervals of approximately six weeks, and at each weighing faeces were collected from approximately 50 per cent of the cattle in each study, the same animals being sampled on each occasion. In each study, pooled faecal samples from each treatment group were cultured for identification of parasitic nematode larvae. Geometric mean faecal egg counts in control groups were generally low throughout the study, reaching a peak mean count of 703 eggs per gram on Day 123. Three control cattle in one study and one in another study were salvage treated with ivermectin to avoid development of overt parasitic gastroenteritis. With the exception of these four cattle, the controls in all studies maintained a healthy appearance, suggestive of a low parasite challenge. Larval differentiation demonstrated that Cooperia and Trichostrongylus were the predominant parasite species throughout the trial period, regardless of region. In contrast Ostertagia was present in each trial but at low prevalence and generally in only the latter period of the trials. Average daily weight gains in 6x groups ranged from 355 to 655 grams, in the 4x groups from 323 to 636 grams and in control groups (1x) from 211 to 538 grams. In all trials the 4 and 6x treated groups gained significantly more weight than the control animals (p<0.05). In all trials the 6x group gained weight at a greater rate than the 4x group. In one study the weight gain benefit of the 6x group was significantly better than that of the 4x group (p<0.05) and in the other three studies it was greater, but the difference was not significant. In each study, the 6x groups had a higher mean valuation than the other groups. Overall, dollar valuations per head ranged lowest to highest from the control to the 6x treated group. The valuations emphasise the significant impact parasitism can have on beef weaners in New Zealand in their first year of life and demonstrate the substantial economic impact of subclinical parasitism. In these trials, the treatment of beef weaners with ivermectin topical solution at 6-weekly intervals, from weaning through to mid-spring, was beneficial for improving weight gains, animal values and parasite control.

Effect of feeding level on the seasonal liveweight gain of young red deer (Cervus cervus) and red/elk hybrid stags - Judson HG; Nicol A (Proceedings of the New Zealand Society of Animal Production, 1997)
Elk (Cervus elaphus ssp.) are becoming increasingly popular as a terminal sire for crossing with New Zealand red deer (Cervus elaphus). Hybrid offspring are significantly heavier at weaning and have a faster post-weaning liveweight gain. However no formal comparisons of liveweight gain responses of red deer and hybrids to pasture allowance have been made. The aim of this work was to compare the growth rate of young red deer and red/elk hybrid stags over a range of nutritional levels during 3 seasons. Single species groups (10-12) of red deer and hybrid weaner stags were offered one of four pasture allowances under rotational grazing for a period of 9 weeks in the winter (June-July), spring (October-December) and summer (February-March). Stags were weighed and given a new allocation of pasture weekly. Pasture allowance ranged from 0.08 to 0.51 kg DM/W0.75/day and pre-grazing pasture mass from 800 to 4500kg DM/ha.

Effect of hormonal environment at emergence on persistence of ovarian follicles in cattle - Day ML; Burke CR; Nation DP; Rhodes FM; Macmillan KL (Proceedings of the New Zealand Society of Animal Production, 1997)
Reduced fertility often occurs when progestins are used to control the timing of oestrus in cattle and is espe-cially evident when a corpus luteum (CL) is not present in the ovary (Kinder et al., 1996). The lowered conception rates at the synchronised oestrus are associated with the development of abnormally large, “persistent” ovarian fol-licles as a result of increased secretion of LH. An under-standing of the endocrine regulation of persistent follicles is essential for development of methods to prevent ovula-tion of this aberrant structure in progestin-based oestrous control systems. The influence of time of luteal regression relative to follicle emergence on persistence of dominant follicles was evaluated in progestin-treated cows.

The effect of level of feeding during rearing on the first lactation milk yield of Friesian replacement heifers. - Penno JW; MacDonald KA; Bryant AM (Proceedings of the New Zealand Society of Animal Production, 1997)
Six nutritional regimes were imposed on Friesian heifers (n=270) from weaning to 22 months of age to determine the effect of level of feeding during rearing on subsequent milk production. Nutritional treatments resulted in groups weighing 480, 406, 455, 376, 398, and 342 kg (P<0.05) at 22 months of age. However, once the heifers entered the herd differences liveweight were lost. By 28 months of age the difference between the heaviest and lightest treatment groups was only 44 kg (P<0.05). Level of feeding from 90 to 200 kg liveweight had no effect on subsequent milkfat or protein yield (P>0.05). Heifers offered a high feeding level after 200 kg produced 9.6 kg more milkfat (P<0.01) and 6.6 kg more protein (P<0.01) than heifers offered the low feeding regime. These data suggest that Friesian heifers produce an additional 0.12 kg MS over their first lactation for each additional 1 kg liveweight gained during rearing.

Effect of mil production and liveweight of feeding balanced or unbalanced supplements to cows grazing restricted summer pasture - Neil PG; Thomson NA (Proceedings of the New Zealand Society of Animal Production, 1997)
To test whether supplementing summer pasture with a balanced ration would improve milk production and liveweight compared to supplementing with silage, four groups of 12 cows were offered with grazed pasture (P), P plus silage (S), P plus a ration which balanced the diet for crude protein (CP) and carbohydrate (PB), or P plus a ration which balanced the diet for neutral detergent fibre (NDF), non structural carbohydrate (NSC) and CP, (CB). The S, PB and CB treatments produced similar milk and milk protein yields, which were higher (P<0.01) than P. Milk fat yield for PB and CB was higher (P<0.001) compared to P but not compared to S. The average liveweight gain for S and PB was 16 kg higher (P<0.01) than P. No improvement in milk production was observed to feeding supplements which balanced either total carbohydrate and CP or NDF, NSC and CP compared to silage supplements.

Effect of nitrogen fertiliser and concentrate feed on dairy production. - Thomson NA; Johnson RJ; Clough J; McCallum DA (Proceedings of the New Zealand Society of Animal Production, 1997)
Over three dairy seasons (1993/94-1994/95) the input of additional N fertiliser (149 kg N/ha) and dairy meal (570 kg meal/cow) was evaluated in dairy farm systems with calving commencing on 20 June. Four farm systems were evaluated: Control LS (no extra N fertiliser, stocking rate, 3.6 cows/ha), NLS (21 kg N/ha after every grazing September to January, 3.6 cows/ha), NHS (N fertiliser same as NLS, 4.2 cows/ha) and NMHS (N fertiliser same as NLS, dairy meal fed at 0.5-3.0 kg/cow/day depending on pasture availability, 4.2 cows/ha). Each farmlet received a base application of 100 kg N/ha; 40 kg N/ha in March and 60 kg N/ha in July. The additional 146 kg N/ha increased (P<0.01) milksolids production by 107 kg/ha, or an additional 0.73 kg MS/kg of N fertiliser applied. The increased milksolids resulted mainly from increased pasture conserved (average of 192 kg DM/cow) which when fed out in summer/early autumn resulted in an increased lactation length of 17 days. A comparison of the NHS and the NMHS treatments showed that the feeding of dairy meal (ME, 13.7 MJ/kg DM and 11.1% crude protein) increased (P<0.01) milksolids production by 77 kg/cow. An increase of 136 g MS/kg of meal fed. The advantage to meal feeding occurred throughout lactation but more in late lactation where lactation length was extended by 35 days. The greater proportion of the response to additional feed inputs from an increase in lactation length rather than an increase in production/cow/day.