@conference {3678, title = {BRIEF COMMUNICATION: Genetic evaluation for milking performance in a large flock of milking sheep in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {74}, year = {2014}, month = {06/2014}, pages = {55-57}, address = {Napier}, issn = {1176-5283}, author = {McMillan WH and McLachlan SJ and Hercus IS and Lopez-Villalobos N} } @conference {3678, title = {BRIEF COMMUNICATION: High milk production in milked sheep grazed in large flocks in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {74}, year = {2014}, month = {06/2014}, pages = {52-54}, address = {Napier}, abstract = {

There is a paucity of published information in New Zealand (NZ) sheep on milk production in commercial-scale dairy enterprises. Much of the early research involved small numbers of animals focused on traditional breeds, with the Dorset breed considered the most suitable dairy-type sheep (e.g., Geenty \& Jagusch 1974). Importation of East Friesian sheep in the mid-1990s provided new opportunities for sheep dairying (Allison 1996). Since that time, there appears to be a limited number of papers published in NZ on the milking performance of animals of East Friesian origin (e.g., Newman \& Steiffel 1999; Peterson et al. 2005)...

}, issn = {1176-5283}, author = {McMillan WH and McLachlan SJ and Hercus IS and Lopez-Villalobos N} } @conference {75889, title = {An economic appraisal of sex-sorted semen in New Zealand dairy herds}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {71}, year = {2011}, month = {Jan}, pages = {131-135}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Invercargill}, abstract = {An economic appraisal was undertaken of female enriched dairy semen in New Zealand commercial dairy cattle. Artificial insemination (AI) scenarios were evaluated in cows (C) and yearling heifers (H) with normal (N-) or sex-sorted semen (S-) with a female enrichment ratio leading to 75\% (S75) or 90\% (S90) heifer calves at birth. In-calf rates with S-semen were 0.75 of normal. Scenarios examined were: cows inseminated with N-semen and yearling heifers naturally mated (CN); cows inseminated with S-semen (CS75 and CS90); cows and yearling heifers inseminated with N-semen (CN-HN); and cows inseminated with N-semen and yearling heifers with S-semen (CN-HS75) and (CN-HS90). These scenarios required 29, 24, 19, 20, 19, and 17 days of AI in cows, respectively. S-semen reduced six-week in-calf rate and final calving rate. The total costs, including reproduction losses, semen and insemination, of producing a four-day old AI heifer replacement calf in a herd of 400 milking cows were $70, $262, $292, $69, $129 and $143. Maximum genetic gain in the milking herd is achieved using S90 semen in the highest genetic merit cows, although this is uneconomic at current semen prices. S-semen has a limited role in New Zealand dairy herds.}, issn = {1176-5283}, author = {McMillan WH and Newman MG} } @conference {41958, title = {Development of large scale commercial AI for genetic improvement in farmed red deer in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {82-90}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Experienced bovine AB technicians can be readily trained to successfully perform trans-cervical AI in red deer. Stags of all ages, including yearling spikers, can produce semen of acceptable quality and quantity at regular intervals from as early as February until mid-winter. Pregnancies rates to a single fixed-time insemination are typically 60-75\% with unknown herd factors contributing much of the variation. Yearling hinds are capable of acceptable pregnancy rates when inseminated in late February, at least a month earlier than is current practice. Within broad limits, considerable flexibility appears to exist when hinds are inseminated relative to the end of synchrony treatment.A deer-specific intra-vaginal progesterone-releasing device has been shown to provide higher terminal levelsof circulating progesterone compared with existing devices. Current field trials will determine its affect onpregnancy rates. We conclude that the genetic and reproductive technologies for increasing weight-for-age in deer have been successfully integrated and applied to commercial red deer in New Zealand.}, issn = {1176-5283}, author = {McMillan WH and Asher GW} } @conference {41124, title = {Are cattle capable of producing litters of calves?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {216-218}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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 {\textpm} s.e. number of conceptuses per pregnant recipient was 2.5 {\textpm} 0.6 and 10.8 {\textpm} 0.8 (P<0.001) in recipients receiving either 5 or 15 embryos. Overall, 63 {\textpm} 4\% of embryos survived (mean {\textpm} 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 {\textpm} 10\%, 77 {\textpm} 5\% and 68 {\textpm} 5\%, respectively, X{\texttwosuperior} = 3.67, NS). Survival was inexplicably lower on Day 22 in recipients receiving 5 embryos (24 {\textpm} 9\% vs. 69 {\textpm} 4\%, X{\texttwosuperior} = 19.15, P<0.001). Pregnancy rate was similar in heifers receiving either 5 or 15 embryos (9/9 vs. 8/10, X{\texttwosuperior} = 2.01, NS), and the mean {\textpm} se number of conceptuses per pregnant recipient was 2.5 {\textpm} 0.6 vs. 10.8 {\textpm} 0.8, (P<0.001). In Expt 2, embryo survival was 80 {\textpm} 5\% and 73 {\textpm} 2\% (NS), and the mean {\textpm} s.e. number of conceptuses per pregnant recipient 1.6 {\textpm} 0.2 and 7.3 {\textpm} 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. }, issn = {1176-5283}, author = {McMillan WH and Peterson J and Thompson J and Pugh PA} } @conference {41123, title = {Embryo and recipient contributions to pregnancy loss following the transfer of cloned embryos derived from foetal and adult somatic cells}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {211-215}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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 ({\textquoteleft}Lady{\textquoteleft} 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. }, issn = {1176-5283}, author = {McMillan WH} } @conference {41112, title = {The Evolution of Liveweight Variance in Angus Steers and Strategies for Control.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {173-176}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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{\textquoteleft}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. }, issn = {1176-5283}, author = {Pleasants AB and McMillan WH and Barton RA} } @conference {41127, title = {A methodology for dealing with uncertain outcomes when applying embryo technologies}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {226-228}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {High variability in number of embryos collected per donor has implications when programming recipients for {\textquoteleft}fresh{\textquoteleft} 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. }, issn = {1176-5283}, author = {McMillan WH and Vivanco HW} } @conference {41042, title = {Development of an experimental herd for investigating maternal contributions to fertility in recipient cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {248-251}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {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 {\textpm} s.e. pregnancy rate of the High and Low groups were 0.77 {\textpm} 0.07 vs. 0.11 {\textpm} 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.}, issn = {1176-5283}, author = {McMillan WH and Donnison MJ and Cox SF} } @conference {40936, title = {Expected pregnancy rate in recipient cattle, sheep and goats derived using a model incorporating embryo and maternal contributions to embryo survival}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {218-221}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Pregnancy rate to term after embryo transfer (ET) in cattle ranges from 30-50\%. A model is proposed which partitions embryo survival into independent and binomial embryo and maternal components. Parameters for these two components can be used to calculate expected pregnancy rates. In 35 out of 36 sets of data in which pregnancy data were recorded following contemporary single and twin ET, or single and twin ovulation, expected pregnancy rate was either within 5 percentage units or one standard deviation of observed pregnancy rate. Pregnancy rate changes in single ET recipients or single ovulating females are equally sensitive to changes in the embryo and maternal components. In contrast, pregnancy rate changes in twin ET recipients or twin ovulating females are more sensitive to changes in the maternal component. In conclusion, these data suggest that the model adequately describes embryo survival and pregnancy rates. Accordingly, research to improve the maternal component seems warranted in order to improve reproductive success. }, issn = {1176-5283}, author = {McMillan WH} } @conference {40902, title = {Technology design and marketing: Case studies for beef cattle breeding}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {57}, year = {1997}, month = {Jan}, pages = {112-115}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {An assessment of farmer beliefs and attitudes to predict likely use of new beef breeding cow technologies was undertaken with farmers from Northland, King Country, and Hawke{\textquoteleft}s Bay. In workshops, farmers evaluated the use of twinning through embryo transfer, artificial insemination with sex-sorted encapsulated semen, and terminal sires. The proportions of farmers likely to use the technologies to some extent, were 55, 72, and 83\% respectively. Farmers identified the important interactions that would be expected to occur if the technologies were introduced into typical beef farming systems in their area. Attitudes towards each technology and towards selected technology attributes, indicated important considerations for future development of the technologies. These included their ability to: improve breeding cow returns; achieve easy care calvings; and integrate with sheep enterprise management to provide leafy feed for lambs. Consideration of these attributes in technology research, development, and marketing, is likely to improve technology uptake. }, issn = {1176-5283}, author = {Parminter TG and Wilkinson RS and Tarbotton IS and Carter JC and Perkins AML and McMillan WH and Smeaton DC} } @conference {40857, title = {Calving performance after embryo transfer-induced twinning - a summary of 30 studies}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {358-361}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Twin calving in beef cows has been proposed as a strategy to increase the biological as well as economic efficiency of beef production. The aim of this paper is to summarise the calving performance of cows induced to calve twins following embryo transfer using data from 30 published studies. The pooled data shows that 45, 28 and 27\% of recipients give birth to either 0, 1 or 2 calves resulting in 82 calves born/100 recipients and 47\% of calving cows producing twins. Overall mean embryo survival rate was only 41\%. Compared with recipients which received in vitro-produced embryos, a higher proportion of recipients that received either a pair of in vivo-derived embryos or a single such embryo in conjunction with AI were pregnant (60 vs 43\%) or produced twin calves (52 vs 39\%). In addition, more calves were born (90 vs 60\%). Considerable variation exists in all parameters, particularly the proportion of number of calves born.}, issn = {1176-5283}, author = {McMillan WH} } @conference {40858, title = {Partial failure of multiple ovulations - a question of uterine efficiency or embryo quality?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {362-364}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Amongst individuals that produce multiple ovulations, and conceive, a variable proportion fail to deliver all potential offspring at term. This source of reproductive inefficiency has been termed partial failure of multiple ovulation (PFMO). In the case of twin ovulators, PFMO is manifest as single births. Most reports in the literature have attributed PFMO to uterine capacity or efficiency factors. An alternative model is proposed, in which it is assumed that a given reproductive outcome is determined by independent binomial effects of embryos and uterine/maternal factors. Using this model, it can be demonstrated that PFMO in twin ovulators can only occur because one of the two embryos is not competent to survive - that is, the uterine/maternal component plays no role in determining variation in PFMO. It follows that in pregnant farm animals with twin ovulations 100\% twin births is possible, but is only constrained by low embryo quality. All published data examined to date in sheep cattle and goats are consistent with this alternative model.}, issn = {1176-5283}, author = {McMillan WH} } @conference {40865, title = {Winter feeding of twinning beef cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {382-385}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {A grazing trial was conducted in southern North Island hill country during 1994, to determine the influence of pasture allowance during winter on cow/calf performance of 40 twin- (T) and 40 single-calf (S) bearing Friesian-cross beef cows. Groups of T and S cows were grazed at low (L), medium (M) and high (H) pasture allowances for the last 4 months of gestation. Average LW in late autumn was 467 kg, and change up to 4 weeks pre- calving was LS -7.8\%, MS -2.4\%, HS +1.5\%, LT -8.1\%, MT -3.0\%, HT - 3.5\%, suggesting S cows responded to a increased pasture allowance in late gestation, but T only to M and no further to H. Blood serum bOH concentration, which was used as a measure of energy status, was not influenced by allowance treatment, but T (2.2 mmol/l) had higher concentrations than S (0.9). Twinning cows had a shorter gestation length than S cows (277 vs 284 d). Twin calves were lighter at birth (30.9 vs 44.2 kg), had lower perinatal survival (73 vs 96\%), and grew more slowly to 4 months of age than single calves (0.76 vs 1.11 kg/d). Our results suggest that }, issn = {1176-5283}, author = {Lambert MG and Devantier BP and Betteridge K and McMillan WH and Pugh PA} } @conference {40718, title = {Bio-impedance monitoring of genital tissues of cows as an aid in cattle reproductive management - a review}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {221-223}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {Lehrer AR and Lewis GS and McMillan WH and Aizinbud E} } @conference {40731, title = {Effect of Monensin capsules on blood metabolites near calving in twin- pregnant and single-pregnant beef cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {265-267}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The aim of this study was to test the hypothesis that Rumensin capsules administered during late pregnancy would have equally beneficial effects in single- and twin-pregnant beef cows, on circulating levels of beta- hydroxy butyrate (BOH), magnesium (Mg) and glucose. Forty cows, half of which were twin pregnant, were treated with either a single Rumensin capsule from a mean of 66 d prior to calving, or remained as untreated controls. Plasma samples were taken on d66, 38, 23, 13 and 5 prior to calving. Rumensin lowered BOH concentration by the second sampling time (0.53 vs. 0.765 mmol/l, P<0.01) and maintained this concentration until calving. Rumensin was without effect on Mg or glucose concentrations. The effects of Rumensin were additive to those of pregnancy status (twin vs. single) for all three metabolites thus confirming our hypothesis. Rumensin may therefore be useful in the late pregnancy management of twin pregnant cows. }, issn = {1176-5283}, author = {McMillan WH and Oakley AP and Hewitt W} } @conference {40699, title = {Estimated pasture intake and cow output of single and twin calving beef breeding cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {161-164}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Thirty-eight adult Merino breeding ewes were drenched with Ivomec and given a controlled release anthelmintic (benzimidazole) capsule in August 1992 and December 1993. Mean FEC in the Untreated group peaked over lambing at 600epg in 1992 and 800epg in 1993. Mean FEC in the Treated group remained below 50epg during the active period of the capsule. The Treated ewes had a higher survival rate, were heavier, grew more wool from late July 1993 and weaned more and heavier lambs in 1993 than the Untreated ewes. At a mean Merino wool price of 500c/kg greasy, returns from the increased wool production more than equates with the anthelmintic treatment cost. Increased returns would be gained from improve ewe survival and increased lamb production. }, issn = {1176-5283}, author = {Bown MD and Clayton JB and McMillan WH and Smeaton DC} } @conference {40730, title = {Induction of early post-calving ovulation and oestrus in suckled beef cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {55}, year = {1995}, month = {Jan}, pages = {261-264}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The aim of this study was to compare the efficacy of exogenous progesterone, either without or with a single injection of gonadotrophin releasing hormone (GnRH), at initiating early post-calving ovulatory and oestrous activity. Six days (d)after the first post-partum follicle had attained dominance cows were allocated to either an untreated control group; treated with a progesterone-impregnated CIDR}, issn = {1176-5283}, author = {McMillan WH and Hall DRH and Oakley AP} } @conference {40632, title = {Current and emerging reproductive technologies for beef breeding cows.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {345-350}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Reproductive technologies may be defined as any technology which impacts on the reproductive potential of the herd. Reproductive technologies applicable to beef breeding cows can broadly be classified into those requiring either a low, medium or high technical input. The examples of {\textquoteright}Low Technology{\textquoteright} options discussed are: age at first joining, breed/cross or strain of cow, time of calving, and pregnancy diagnosis. In traditional breeding cow herds, cow productivity can be increased by modest amounts (5-10\%) if only single-option {\textquoteright}low tech{\textquoteright} changes are implemented. However, these fundamental technologies need to be well developed before higher technologies can be successfully applied. Two examples of {\textquoteright}Medium Technology{\textquoteright} strategies that have been available for some time include oestrous synchronisation and multiple suckling. Oestrous synchronisation has the potential to facilitate an increase in the number of herds adopting yearling heifer mating. Twin suckling through fostering an additional calf has been demonstrated to significantly increase the number of calves weaned per cow. Emerging {\textquoteright}High Technology{\textquoteright} options include: twinning, controlling the sex of calves at conception and cloning. Future developments in embryo technologies are vital in many of the emerging reproductive technologies for beef cows. }, issn = {1176-5283}, author = {McMillan WH} } @conference {40634, title = {Determining the number of calves in early pregnancy using real-time ultrasound imaging in beef cows induced to twin.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {353-356}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Details of the timing of pregnancy loss following induced twinning are unknown. The aim of this study was to evaluate real-time ultrasound as a method of determining early pregnancy status (0, 1 or 2 foetuses) in beef cows induced to twin using AI and ET. A 7.5 Mhz ultrasound probe was used intra- rectally to count foetuses in 2 experiments. In Exp. 1, 57 heifers were examined between 25 and 60 days of pregnancy and then slaughtered. In Exp. 2, up to 103 cows were examined between Day 25 \& 60 of pregnancy, and final pregnancy status was confirmed using calving records. In Exp. 1, the accuracy of Day 25, Day 45 and Day 60 predictions of 2 foetuses was 100\%, 20\% and 100\%, and 1/24, 5/33 and 1/33 twin pregnant heifers were predicted. The accuracy of correctly predicting twin outcomes was 33, 50 and 33\% at the same 3 stages of pregnancy, but only 3, 2 and 3 twin pregnancies occurred, respectively. In Exp. 2, there was generally little difference between the accuracy of predicting twin pregnancies and the accuracy of the prediction. Thus, at Day 25, 35 and 45 and 60, the accuracies were approximately 20, 47, 52 and 45\%. Twenty recipients eventually calved twins. We conclude that real-time ultrasound imaging up to Day 60 is not an accurate technique for determining twin pregnancy status of cows. Loss of concepti between scanning and term did contribute substantially to this poor result in Exp. 2, but not in Exp. 1. }, issn = {1176-5283}, author = {McMillan WH and Oakley AP and Hall DRH} } @conference {40633, title = {In vitro production of cattle embryos: Use in beef twinning programmes.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {351-352}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This study investigated the survival of in vitro derived embryos as single or twin pregnancies following their twin transfer to recipient cows. Abattoir-derived oocytes were matured, fertilised and then cultured for 6-7 days using our standard laboratory procedures. One hundred and forty good quality late morula and blastocysts were transferred non-surgically, in pairs, to recipient cows on day 7 of the oestrous cycle (day 0 = oestrus). Recipients were monitored by ultrasound for pregnancy up to Day 60 and embryo survival was determined. While 57 (81\%) of recipients did not show oestrus by day 21, only 39 (56\%) were pregnant on day 35 and 30 (77\%) of the pregnancies were twins (embryo survival; 57\%). Increasing stage of gestation was associated with a decrease in pregnancy rate, twin pregnancies and embryo survival (46\%, 37\% and 31\%, respectively) on day 60. The results show that while high initial pregnancy rates can be established following the transfer of two in vitro derived embryos, embryo survival drops during early pregnancy. Current research efforts are investigating factors that may influence early embryo survival in cattle. }, issn = {1176-5283}, author = {Pugh PA and Thompson JG and McGowan LT and McMillan WH and Tervit HR} } @conference {40560, title = {Timing single fixed-time inseminations in ewes: Some new concepts}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {54}, year = {1994}, month = {Jan}, pages = {45-50}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The mean interval from the end of synchrony treatment to the onset of oestrus can be highly variable and as a consequence {\textquoteright}single-time{\textquoteright} inseminations may occur at other than optimal times. This study was undertaken to identify some of the factors influencing the interval to oestrus following synchrony treatment, and to develop a spreadsheet model to assist with determining the timing of AI in ewes under a range of oestrous onset patterns. Synchrony device, PMSG, time of year, and live weight tended to have important effects on the interval to oestrus. Ewe genotype and year effects were generally small. Three new concepts have arisen from the modelling exercise. Firstly, the actual timing of AI to achieve near maximum fertility depends on the mean interval to oestrus in a given flock, but not the precision of synchrony or the incidence of ewes that are synchronised. Secondly, the {\textquoteright}tolerance{\textquoteright} about this optimum time of insemination depends on how much is known about the mean interval to onset (more information means more tolerance). Thirdly, the {\textquoteright}tolerance{\textquoteright} about this optimum time of insemination depends on the maximum reduction in flock pregnancy rate that is acceptable to the flock owner (higher reduction means more tolerance). If the onset pattern in a particular flock is unknown, the {\textquoteright}universal{\textquoteright} timing for a single fixed-time AI during the breeding season is 42- 46 h after CIDR{\AE} removal, provided a drop in flock pregnancy rate of up to 5\% is acceptable. }, issn = {1176-5283}, author = {McMillan WH} } @conference {40503, title = {Changing the sex ratio at birth in lambs, calves and deer: Implications for productivity and genetic gain in breeding flocks and herds in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {259-262}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Progesterone (P4), oestradiol benzoate (ODB) and prostaglandin F2a (PGF) have been used separately and in combination to synchronise oestrus in cattle by reducing the luteal phase of the cycle or delaying pro-oestrus after luteolysis. This latter mechanism can result in precise synchrony but with reduced fertility. In the process of attempting to improve synchrony and fertility, a series of four trials was completed with dairy heifers. Each trial was based on the use of a CIDR-B device for 7 to 10 days with or without 10 mg ODB in a gelatin capsule and with an injection of PGF from 2 to 4 days before device removal or at device removal. The results of these trials showed that injecting PGF before device removal could improve synchrony (in terms of animals inseminated at 48 h after device removal) but reduced pregnancy rates to first insemination by 5\% to 10\%. Incorporating ODB delayed the post-treatment interval to oestrus and insemination with a 7-day CIDR regime but improved synchrony with a 9 or 10 day CIDR regime. If the use of ODB was combined with an injection of PGF 4 days before CIDR device removal as part of a 10-day CIDR programme, the 48 h post-treatment synchrony rate was 93\% and the pregnancy rate was 56\%. Excluding the ODB from this programme reduced the 48 h synchrony rate to 87\% and the pregnancy rate to 45\%. These results are additional evidence that combing ODB with P4 is altering ovarian follicle wave patterns with consequent effects on synchrony patterns and fertility.}, issn = {1176-5283}, author = {McMillan WH} } @conference {40504, title = {Twinning in beef cows: preliminary results from embryo transfer studies}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {263-266}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {While the main focus in the breeding of Texel sheep in New Zealand has been selection for superior meat production there are significant qualities in the wool which make it a highly desirable fibre. Texel, Texel X Romney and Romney wools are evaluated to determine their relative attributes as textile fibres in wool products where good length and high bulk are considered important. Evaluation involved examining the value of good length bulk wool in the current wool market, spinning semi-worsted yarns, manufacturing carpets and sample bedding products. All three lines performed as expected from the measured fibre characteristics. Core bulk of the scoured wool for Texel, Texel X Romney and the Romney were respectively 32.9 cm3/g, 29 cm3/g and 25.7 cm3/g. Based on an average market value of 450 c/kg clean and 1991/92 relativities, the premium for bulk of these long good colour wools is 10 c/kg/unit. The high bulk wools gave improved spinning performance 44.4 52.9 and 73.3 end breaks per 100 spindle hours at 5000-6000 rpm for the Texel, Texel X Romney and Romney lines respectively. Improved abrasion resistance of carpet made from the Texel and Texel-cross was attributable to different pile weight and yarn bulk values. Samples evaluated indicate Texel sheep produce wools with similar textile properties to New Zealand crossbred wools but with higher bulk. The Texel breed should be monitored for its suitability as a source of genetic material to increase bulk in New Zealand wools. Lack of quantitative knowledge of the change in fleece weight and carcass returns from the introduction of the Texel genetic influence into Romney stock prevents assessment of their economic benefit to the New Zealand farmer.}, issn = {1176-5283}, author = {McMillan WH and Hall DRH and Evans PH and Day AM} } @conference {40489, title = {Twin-suckling beef cows using foster calves: effects on cow and calf performance}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {203-205}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {One hundred and twenty three Friesian or Friesian x Jersey mature dairy cows were used to examine the effects of Rumensin Anti- bloat Capsules (ABC), containing sodium monesin on plasma magnesium, glucose and }, issn = {1176-5283}, author = {McMillan WH and Evans PH and Hall DRH and McLean M} } @conference {40399, title = {Modelling herd efficiency in liveweight-selected and control Angus cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {52}, year = {1992}, month = {Jan}, pages = {145-148}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The growth and sexual development of red deer calves born early (12 male, 12 female), with an average birth date of 22 October 1990 }, issn = {1176-5283}, author = {McMillan WH and Morris CA and McCall DG} } @conference {40378, title = {Reproduction in flocks selected for and against lamb faecal egg count}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {52}, year = {1992}, month = {Jan}, pages = {65-68}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The calpain system consists of two enzymes and their endogenous inhibitor, calpastatin, and is involved in the breakdown of myofibrillar protein in skeletal muscle. We have investigated the relationship between the calpain system and protein degradation in sheep under three different feeding regimes. Calpain were separated from fresh muscle using a DEAE-Sephacel ion exchange column. Calpain I and calpastatin activities were higher in the restricted group than in the ad- libitum group. Fasting increased calpastatin but had no effect on the calpain I activity. There was a positive relationship between the calpastatin : calpain I ratio and protein degradation and a negative relationship with calpain I. This result is at variance with the idea that calpain I activity limits the rate of protein degradation. }, issn = {1176-5283}, author = {McMillan WH and Hall DRH and Watson TG} } @conference {40322, title = {Are yearling heifer mating and more productive beef cow breeds a worthwhile use of winter feed?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {51}, year = {1991}, month = {Jan}, pages = {265-270}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {A computer software package (REVGAIN) is being developed to integrate closely with Animalplan. It assists breeders and their advisers to derive relative economic values and selection criteria to suit their breeding programme. For farmers buying flock rams REVGAIN derives relative economic values for their individual commercial flock, and hence the sort of breeder from which to buy rams. Using specific production levels, prices, and costs for the producers{\textquoteright} or breeders{\textquoteright} situation, together with the corresponding Animalplan phenotypic and genetic parameters, the software calculates relative economic values that will lead to maximum economic progress in the breeding goal. It also estimates the change in each character that will occur from a standard amount of index selection. By comparing different economic outcomes from changing product prices, physical inputs or genetic responses, users derive the policy that is most appropriate to their particular situation. }, issn = {1176-5283}, author = {McMillan WH and McCall DG} } @conference {40298, title = {Superovulation in ewes: are follicle numbers a useful predictor of ovulation rate?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {51}, year = {1991}, month = {Jan}, pages = {133-138}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The grazing behaviour of mixed age cashmere producing does was recorded on pasture dominated hill country at six physiological stages; post-weaning, pre-mating, early pregnancy, late pregnancy, early lactation and mid lactation. Observations were conducted from sunrise to sunset on three consecutive days at each physiological stage. Activity, land slope, time and position of focal animals were recorded. Flock position over the study site was also registered. At each physiological stage grazing was the predominant activity (34-63\% of the time observed). The major grazing period occurred during the afternoon. Grazing occurred predominantly on steep and easy slopes (>70\% of the time observed). Pasture height influenced the goats preference for the slope grazed. The does travelled in a regular pattern around the study site. This pattern was less distinct when the does had kids at foot. Activities observed during late pregnancy differed considerably from activities observed at other physiological stages. Some of these differences included more time spent standing and no distinct afternoon grazing period. Rain was the main event to interrupt grazing and initiate a change in the movement pattern of the does. }, issn = {1176-5283}, author = {McMillan WH and Hall DRH} } @conference {40146, title = {CIDR-B for managed reproduction in beef cows and heifers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {49}, year = {1989}, month = {Jan}, pages = {85-90}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {There is a long-standing disagreement about the influence that feeding has on body composition, particularly in ruminants, yet the problem remains of finding ways to produce lean lambs. This paper attempts to revive the view that feeding can alter, independently, the rate of growth and the relative rate of fattening in sheep. A numerical illustration is given of the relationship between a lamb{\textquoteright}s potential for growth, its feed requirements and the rules it uses to partition feed resources when they are scarce. For simplicity, the feed is considered only in terms of its metabolisable energy; digestible crude protein ratio. Published data are then review to test whether it is reasonable to retain the proposed theory. The review closes with a discussion of our current options and future possibilities for changing body composition by feeding.}, issn = {1176-5283}, author = {McMillan WH and Macmillan KL} } @conference {40139, title = {Do melatonin implants influence the breeding season in Coopworth ewes?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {49}, year = {1989}, month = {Jan}, pages = {43-46}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Although the Booroola F gene increases litter size in the ewes by one lamb there have been no unequivocal reports of its expression in the ram. In this report the presence of the F gene in the ram has been shown to increase sperm swimming speed and a sperm activity index as measured by a dual and single beam laser respectively. The lambing rate of ewes artificially inseminated with sperm from rams with the FF genotype was slightly higher than those inseminated with sperm from rams without the F gene.}, issn = {1176-5283}, author = {McMillan WH and Sealey RC} } @conference {40183, title = {Lambing of Romney and Booroola cross hoggets with and without the F gene under different pasture allowances}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {49}, year = {1989}, month = {Jan}, pages = {281-284}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Ruminants grazing pasture rarely approach their genetic potential for meat, milk or wool production. There are wide differences also between plant species and between leaf, stem and inflorescence fractions in their capacity to sustain animal production. The relatively low productivity of grazing ruminants and the differences between plant components in nutritional value can be explained from an understanding of the factors that determine nutrient supply to the animal{\textquoteright}s tissue and the efficiency of metabolism. Nutrient supply to the tissues depends on Ii) the nutrient contents of the forage available, which varies between plant species, their component parts, their stage of maturity and the growing conditions; (ii) the pasture components actually selected by the animal which are influenced by ease of eating, taste, odour and tactile characteristics of the plant material available, its water content, the structure of the sward, the dimensions of the animal{\textquoteright}s incisor arcade and its previous experience; (iii) the amount of each selected component eaten, which is influenced by the potential of the animal to utilize nutrients, the capacity of the reticulo-rumen and factors that affect the rate of digestion and outflow of organic matter from the rumen, and the time spent in eating and ruminating activities; (iv) modifications of consumed nutrients by rumen microbes, particularly the extent of breakdown of plant protein and the relative proportions of volatile fatty acids produced; (v) the efficiency of biochemical reactions metabolising the absorbed nutrients. Although a great deal is known about the way each of these factors influence nutrient supply to grazing animals, the complexity of the interactions between them often makes it extremely difficult to identify the specific reasons for reduced performance in any particular situation. However, by integrating current concepts and knowledge using computer simulation techniques, the factors limiting nutrients supply to the animal{\textquoteright}s tissues can be determined and the value of alternative management strategies for improving animal productivity assessed. }, issn = {1176-5283}, author = {Moore RW and McMillan WH and Dockrill G and Dow BW} } @conference {40178, title = {Mating Romney ewes in November-December using CIDRs and pregnant mare serum gonadotrophin}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {49}, year = {1989}, month = {Jan}, pages = {255-260}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The policy on most New Zealand sheep farms is to pre-tup shear two tooths in late February/early March two to four weeks prior to mating. However, in summer-dry regions, where feed supplies are typically low in late summer, this practice may potentially depress two tooth performance because post-shearing increases in feed requirements cannot be met. An alternative hogget-four tooth shearing arrangement which does away with late summer/autumn two tooth shearing has therefore been investigated at Massey University{\textquoteright}s "Riverside" sheep farm in the Wairarapa; a farm prone to summer droughts. In trials over three years the alternative shearing arrangement was found not to disadvantage ewe liveweight gains, fertility, wool production or financial returns. In addition to reducing autumn feed requirements, earlier objective selection of flock replacements and hogget mating are potential benefits of the alternative shearing programme. A slightly poorer spring cashflow results but otherwise management requirements are similar.}, issn = {1176-5283}, author = {Knight TW and McMillan WH and Kannegieter SG and Sorensen ES and Ridland CJ and Gibb M} } @conference {40087, title = {Early growth and reproduction of exotic sheep breeds - a preliminary report}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {48}, year = {1988}, month = {Jan}, pages = {49-52}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, issn = {1176-5283}, author = {McMillan WH and Malthus IC and Clarke JN and Amyes NC} } @conference {40105, title = {Sporidesmin poisoning in ewes during late pregnancy}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {48}, year = {1988}, month = {Jan}, pages = {131-134}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Forty-eight animals were allocated to 1 of 3 treatments (C = continuous growth; I = infected with 4000 larvae/d of Trichostrongylus colubriformis; P= individually paired with I animals for change in live weight) in a serial slaughter experiment examining the effects of intestinal parasitism on bone and muscle in young growing sheep (25 to 45 kg). Both I and P groups were nutritionally rehabilitated after the I group had undergone an 83 d period of infection. While I and P groups underwent similar changes in live weight during the period of infection, feed intake of the P group became progressively less than that of the I group. By the end of infection I animals were consuming approximately 30\% more feed than P animals. During the period of infection both I and P groups lost live weight. Of the body chemical components, fat was depleted to the greatest degree (48\% loss) followed by protein (23\% loss). While bone displayed growth in external linear dimensions (length = +4\%; diameter = +6\%) there were significant reductions in protein (22\%) and cortex width (33\%). In contrast muscle showed decreases in all chemical components and in diameter. This greater effect on muscle was exaggerated in the I group. Infection led to greater reductions in muscle protein (45\% v 34\% (I v P)) and muscle diameter (19\% v 8\%). There were no appreciable differences between the I and P groups for changes in bone variables. While specific effects of infection on growth of muscle were found, change in most variables was largely attributable to the general restriction in growth consequent upon undernutrition. Subsequent to the period of parasitic infection, compensatory growth occurred such that muscle recovered relative to bone. There was some evidence that full recovery of muscle relative to bone was delayed in animals recovering from a parasitic infection.}, issn = {1176-5283}, author = {McMillan WH and Dockrill G and Towers NR} } @conference {40073, title = {The male effect - a comparison of rams and bucks for teasing ewes}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {47}, year = {1987}, month = {Jan}, pages = {135-138}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {No abstract supplied}, issn = {1176-5283}, author = {McMillan WH} } @conference {40077, title = {Post-mating progesterone supplementation in ewes and hoggets}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {47}, year = {1987}, month = {Jan}, pages = {151-154}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Castrate male and female lambs (n=8) received no treatment (O dose) or a silicone rubber implant containing 3 mg (L dose), 22 mg (M dose) or 52 mg (H dose) of oestradiol, respectively. Implants were placed subcutaneously at 8-10 weeks of age (mean weight 20.4 kg) and the animals slaughtered 180 d later. Oestradiol treatment decreased length of cannon bone but increased length of vertebral column and 12th rib. Cessation of growth in an early maturing bone (cannon bone) appeared to be accelerated by the treatment so that length was reduced. Later maturing bones (rib and vertebrae) showed a dose-dependent stimulation of linear growth. It is concluded that oestrogens accelerate the natural process of skeletal maturation.}, issn = {1176-5283}, author = {McMillan WH} } @conference {40074, title = {The timing of CIDR withdrawal and ram introduction on ewe fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {47}, year = {1987}, month = {Jan}, pages = {139-142}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {If predictions for future growth of New Zealand{\textquoteright}s exports of chilled lamb meat are to be fulfilled, overall quality will have to be maintained at a consistently high level, and properties like storage life and appearance will require emphasis. A review of scientific literature showed that a wide range of farm practices can influence meat quality. The trend to breed leaner lambs, to slaughter more ram lambs at heavier weights and older ages in winter and spring, and effects of stressful experiences before slaughter, were seen as areas of potential concern for the production of high quality meat. However, it has not been established that these factors are of economic importance to the meat industry. It is suggested that they should be investigated as possible constraints on the future development of markets for premium quality lamb.}, issn = {1176-5283}, author = {McMillan WH} } @conference {40035, title = {The cause of reproductive loss in Gisborne-East Coast ewe flocks}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {46}, year = {1986}, month = {Jan}, pages = {251-254}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {The relationship between lamb growth rate and ewe milk yield was examined using 213 ewe-lamb sets in 6 experiments. Factors included ewe breed, lamb rearing status, herbage allowance, lambing date and season. Lamb growth and ewe milk production were greater for twin- than single- lamb groups, for Dorset than Romney ewe breeds and for late than early lambing dates. Ewe live weight showed the reverse trend. Regression parameters indicated lamb growth rate was generally more dependent on milk supply during the first 6 than during 12 weeks of lactation. The exception was Romney ewes with low milk production rearing twin lambs. Comparisons among groups of regression coefficients and nominal ordinates (i.e. growth rate at low milk yield) showed that twin lambs were proportionately more dependent on pasture for growth than singles as were lambs reared by Romney compared with Dorset ewes. Similarly, a high herbage allowance, good seasonal pasture growth and a late lambing date caused a greater contribution of pasture to lamb growth. However, among groups there was much variability in the relationship and generally lamb live-weight gain was a poor indicating of ewe milk yield (approx. r}, issn = {1176-5283}, author = {Jagusch KT and Gray MM and MacLean KS and Towers NR and di Menna ME and McMillan WH} } @conference {40015, title = {Effects of gonadotrophin releasing hormone (buserelin) on sheep fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {46}, year = {1986}, month = {Jan}, pages = {161-164}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Teaser stags and progesterone-PMS treatments were used to advance the breeding season in non-lactating adult red deer hinds. In Experiment 1, 2 vasectomised stags were run with 39 hinds for 15 d prior to joining with entire stags. More teased hinds (20/39) calved early (11-20 November ) than group of non-teased hinds (5/42). In other experiments, laparoscopy revealed that progesterone + PMS treated hinds ovulated in mid February. Although calves were born as early as 10 October, indicating stags could successfully fertilise a hind in mid February, such treatment did not result in many hinds calving in October. It seems that the stag is sub-fertile in February. Calving dates of contiguous control hinds show that a large proportion were mated 18 to 25 d after the induced oestrus in treated hinds indicating red deer stags can have an effect similar to the {\textquoteright}ram effect{\textquoteright}. Some hinds calving to the induced oestrus produced twins.}, issn = {1176-5283}, author = {McMillan WH and Knight TW and Macmillan KL} } @conference {40029, title = {Hogget oestrus synchronisation: a comparison of CIDR and sponges}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {46}, year = {1986}, month = {Jan}, pages = {225-228}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {At 3 months of age, the ovaries of F+ Booroola lambs [i.e. those heterozygous for the fecundity (F) gene] were lighter (P<0.01) than those of ++ Booroola lambs (i.e. those without the F-gene) which were of similar age and body weight. However, the number of follicles (>/= 1 mm diam.) in the above F+ lambs was 1.5 fold greater (P<0.01) than that in the ++ lambs. In lambs of both genotypes, ovarian follicles were active in synthesising testosterone and oestradiol and of reaching diameters which were similar to those of preovulatory follicles in mature ewes. However, none of the ovaries showed evidence of recent ovulations. In Booroola ewes (4 to 8 years of age), the proportions of small ovarian follicles (0.5 to 1.0 mm diam.) that synthesised progesterone, androstenedione and oestradiol in culture were related (P<0.05) to genotype (homozygous, FF > F+ > ++ ewes). Also in the above ewes, follicles in the FF and F+ animals reached maturity at smaller diameters than in ++ animals, namely 3.4 }, issn = {1176-5283}, author = {McMillan WH} } @conference {39967, title = {Effect of slope on lamb mortality}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {45}, year = {1985}, month = {Jan}, pages = {163-166}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {In the 10 years since it was observed that immunisation of ewes against steroid hormones resulted in an increased ovulation rate, research has provided some understanding of the mechanism of immunoneutralisation and of the factors which influence or modify the immunological and physiological response of ewes. It has also led to the development of a commercial vaccine. The mechanism of action is still uncertain although several changes in the endocrine balance of the ewe may be involved. Active immunisation against a number of steroids has been shown to increase ovulation rate and with passive immunisation, a mixture of steroid antibodies produced the best result. One possible mechanism via a reduced negative feedback on the pituitary and increased gonadotrophin release has been recorded. Effects at the ovarian level influencing follicular atresia must be also considered. The initial attempts at the practical application of this technology were unsuccessful. Although ovulation rates were increased, fewer lambs were born per ewe joined due to problems of anoestrus and anovulation. From these data the relationship between antibody titre and response was established and alterations to the composition of the antigen and treatment schedule were developed to modify the antibody response. Factors such as ewe age, level of nutrition and breed had little effect on the response. The response to changes in nutrition and live weight appear to be additive to those of immunisation, as is the response to exogenous gonadotrophins (PMSG). The timing of treatment relative to mating appears to have some effect, with intervals of less than 21 days reducing the lambing response through a high proportion of barren ewes. However there has been considerable variation in the final response indicating a major effect of early embryonic mortality. Lamb birth rank distribution has been within the predicted range and been seen mainly as an increase in twins with some higher order multiples. The mortality of lambs from treated ewes has been similar to that of lambs of the same birth rank from untreated ewes. The growth and reproductive performance of the progeny from treated ewes has been unaffected.}, issn = {1176-5283}, author = {McMillan WH and Knight TW} } @conference {39973, title = {Ovulation and lambing responses with alternating steroid immunisation over 3 years}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {45}, year = {1985}, month = {Jan}, pages = {187-189}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Immunisation is a potentially profitable technique to improve ovine fecundity. It increases the proportion of multiple bearing ewes and lambs born as multiples. This calls for adequate feeding if production is to be sustained. The technique is therefore likely to have higher net returns in areas with ample summer feed. AS the response to the treatment is variable, the probability of not breaking even with the cost of the drug can be as high as 30\%. Where feed is adequate additional net returns of $1 to $2 per ewe can be expected if the response is a 25\% increase in lambs born per ewe joined.}, issn = {1176-5283}, author = {McMillan WH and Smith JF} } @conference {39815, title = {Hogget lamb mortality}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {43}, year = {1983}, month = {Jan}, pages = {33-36}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Dorset ewes rearing twin lambs were offered herbage allowances of 2, 5 and 8 kg DM/ewe/d during a 6-week lactation period. Ewes and lambs were shifted at 3-day intervals. At 6 weeks lambs were weaned, combined into 1 mob and offered a fresh area of pasture ad lib every 3 days. Lambs were slaughtered at 6, 12 and 18 weeks of age. Carcass weight and fat measurements recorded. There were significant live-weight differences (2.5 kg) between low and high allowances during the trial, but differences in carcass weight were only significant at 6 and 18 weeks. Average growth rate between 6 and 18 weeks was 176 g/d in all groups. Fat measurements suggested no differences in carcass fatness between groups. It was concluded that herbage allowance preweaning had little effect on subsequent lamb growth and carcass fatness when ewes were shifted to new pasture at 3-day intervals.}, issn = {1176-5283}, author = {McMillan WH} } @conference {39764, title = {Shearing and time of joining effects on reproduction in two- tooth ewes}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {42}, year = {1982}, month = {Jan}, pages = {45-46}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Local Merino, 1/4 local Merino and 1/2 local Merino ewes were grazed on oversown and top-dressed tussock grassland. When ranked for lamb and wool productivity at 2 and 3 years of age both the Booroola crosses were superior to the Merino. Satisfactory lamb weights and ewe fleece weights were obtained at lambing percentages above those normally obtained on this class of land.}, issn = {1176-5283}, author = {McMillan WH and Knight TW} }