@article {3672, title = {Growth and milk production of dairy heifers born to two-year-old or mixed-age dams}, journal = {New Zealand Journal of Animal Science and Production}, volume = {79}, year = {2019}, month = {07/2019}, pages = {135-139}, address = {Palmerston North}, abstract = {Keeping replacement heifers that were the progeny of primiparous cows mated by artificial insemination, enhances rates of genetic gain. Heifers that were the progeny of primiparous cows were lighter at birth and grew at a slower rate to first calving compared with heifers born to multiparous dams. Heifers that were heavier before first calving produced more milk than did lighter heifers. This study aimed to determine if there were liveweight (LWT) or milk-production disadvantages for heifers born from primiparous compared with multiparous dams. Data comprised of LWT records from 189,936 New Zealand dairy heifers. Dams were allocated to four groups according to their age: two (2yo; n=13,717), three (3yo; n=39,258), four to eight (4-8yo; n=120,859) and nine years old or greater (>=9yo; n=16,102). Heifers born to 2yo dams were lighter (P<0.01) from three to 21 months of age than heifers born to 3yo and 4-8yo dams. The progeny of 2yo and 3yo dams produced similar milksolids yields during their first lactation (304.9{\textpm}1.6 and 304.1{\textpm}1.5 kg, respectively), but more (P<0.01) than that of 4-8yo dams (302.4{\textpm}1.5) and >=9yo dams (P<0.001; 297.8{\textpm}1.6 kg). Heifers born to 2yo dams were lighter but produced more milk than heifers from older dams.}, issn = {1176-5283}, author = {Handcock RC and Lopez-villalobos N and Back PJ and Hickson RE and McNaughton LR} } @article {3672, title = {BRIEF COMMUNICATION: Reproductive performance of herds milked once a day all season compared with herds milked twice a day all season}, journal = {New Zealand Journal of Animal Science and Production}, volume = {78}, year = {2018}, month = {07/2018}, pages = {170-172}, address = {Lincoln}, abstract = {The objective of this study was to compare the reproductive performance of herds milked once a day (OAD) for the whole season with that of herds milked twice a day (TAD) for the whole season. Herds were classified as OAD or TAD if they herd tested >= three times a season and >90\% of animals had the same milking regime (OAD or TAD) at each test. Once the OAD herds were identified, the closest geographical TAD herd was identified and included in the dataset for the 2014 to 2016 seasons. Only herds with a Detailed InCalf Fertility Focus report were analysed (OAD n=75, TAD n=76). The means of five key reproduction measures were analysed and the means were significantly different for all measures (P<0.001). The OAD herds had a 7.7\% higher mean herd 3-week submission rate (OAD=84.6\%, TAD=76.9\%), 7.9\% higher mean conception rate (OAD=60.1\%, TAD=52.2\%), 10.4\% higher mean 6-week in-calf rate (OAD=74.8\%, TAD=64.4\%), 4.8\% lower mean not-in-calf rate (OAD=12.8\%, TAD=17.6\%), and 4.3\% more of the herd calved by week six of calving (OAD=88.2\%, TAD=83.9\%) than TAD herds. These results indicate that herds milking OAD for the whole season have, on average, better reproductive performance than those milked TAD the whole season.}, issn = {1176-5283}, author = {Hemming NV and McNaughton LR and Couldrey C} } @conference {3672, title = {Calf and heifer development and the onset of puberty in dairy cows with divergent genetic merit for fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {205-210}, address = {Rotorua}, abstract = {A research herd with divergent genetic merit for fertility was established to better understand the underlying drivers of fertility in dairy cattle. This paper describes the establishment of this herd, heifer growth and development, and the effect of divergence in fertility breeding value (FBV) on the timing of puberty. The average FBV of the high and low fertility groups of heifers was +5.6 and -4.6, respectively. The heifers were weighed fortnightly, with body condition score (BCS) and stature recorded at six, nine, 12 and 15 months of age. Weight and age at puberty were defined as the first day when plasma progesterone was >1 ng/ml in two of three consecutive once weekly samples. There was no effect of FBV on live weight (LWT), BCS, nor stature by age as the heifers matured. High-fertility heifers attained puberty at a lighter LWT (271 vs. 296 kg; SED 4.3 kg), an earlier age (358 vs. 379 days; SED 6.0 days) and a lower proportion of estimated mature LWT (51 vs. 55\%; SED 0.7\%), compared with Low-fertility heifers. Therefore, the premise that high genetic merit for fertility is positively associated with reaching puberty earlier is supported. Further work is required to support and assess the value of incorporating a puberty trait into the FBV.}, issn = {1176-5283}, author = {Meier S and Fisher B and Eketone K and McNaughton LR and Amer PR and Beatson P and Bryant JR and Dodds KG and Spelman R and Roche JR and Burke CR} } @conference {3672, title = {Growth curves of New Zealand Holstein-Friesian, Jersey and Holstein-Friesian-Jersey crossbred heifers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {64-68}, address = {Rotorua}, abstract = {There are differences in the proportion of target live weight (LWT) achieved between the main breeds of dairy heifers in New Zealand, suggesting a potential difference in growth pattern. The objectives of this study were to model growth curves of dairy heifers through random regression of Legendre polynomials, and to compare growth curves of the main breeds. Data comprised of 1,653,214 LWT records obtained from 189,936 dairy heifers in 1,547 herds. The fourth-order Legendre polynomial was the best at predicting LWT, with a relative prediction error (RPE) of less than 4\% for the whole dataset and for Holstein-Friesian, Jersey and Holstein-Friesian-Jersey crossbred (F{\texttimes}J) heifers. The regression coefficients of the growth curve differed among breeds for the intercept (α0; P<0.001), linear effect (α1; P<0.001), quadratic effect (α2; P<0.001), cubic effect (α3; P<0.001) and quartic effect (α4; P<0.001). At all ages Holstein-Friesian heifers were heavier than F{\texttimes}J which were heavier than Jersey heifers (P<0.001). The percentage difference among the breeds varied throughout the growth curve, indicating that the main breeds of dairy heifers in New Zealand exhibited different growth patterns that were non-linear. The different growth patterns for each breed should be considered when formulating target LWTs and growth rates.}, issn = {1176-5283}, author = {Handcock RC and Lopez-Villalobos N and McNaughton LR and Edwards GR and Hickson RE} } @conference {3672, title = {The percentage of spring-calving carryover cows in New Zealand dairy herds and their milk production, compared to heifers, age-matched and lactation-matched non-carryover cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {3-7}, address = {Rotorua}, abstract = {Non-pregnant cows are generally culled from dairy herds and replaced with heifers. Alternatively, non-pregnant cows can be dried-off at the end of lactation, retained for one year (carried over), before being mated and returned to a milking herd in the following year. The aim of this study was to estimate the percentage of spring-calving carryover cows in New Zealand dairy herds and to compare their milk production with that of heifers, lactation-matched and age-matched non-carryover cows. Results showed that 2.5\% of spring-calving cows had experienced a previous carryover period. The majority (43\%) of carryover cows had failed to conceive during their first lactation. Most (69\%) dairy herds contained less than 5\% carryover cows and 17\% had zero carryover cows. Second-lactation carryover cows produced 4778.1{\textpm}6.3 L milk, 228.7{\textpm}0.3 kg fat, 182.0{\textpm}0.2 kg protein, and had a somatic cell score (SCS) of 6.31{\textpm}0.01, which was greater (P<0.001) than the milk production of heifers that produced 3514.5{\textpm}5.9 L milk, 168.3{\textpm}0.3 kg fat, 134.0{\textpm}0.2 kg protein, and had a SCS of 5.89{\textpm}0.01. Carryover cow milk production was also greater (P<0.001) than that of lactation-matched and age-matched non-carryover groups. The results of this study will aid on-farm culling decisions.}, issn = {1176-5283}, author = {Gardner RR and Back PJ and Lopez-Villalobos N and McNaughton LR} } @conference {3672, title = {More dairy heifers are achieving liveweight targets}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {76}, year = {2016}, month = {07/2016}, pages = {3-7}, address = {Adelaide}, abstract = {Dairy heifers should reach industry liveweight targets that are set to ensure heifers achieve good reproductive performance and milk production. The aim of this study was to determine if more dairy heifers born between the 2011-12 and 2014-15 dairy seasons (current) in New Zealand are achieving liveweight targets since a study on heifers born between the 2006-07 and 2010-11 dairy seasons (historic). In all age groups the mean live weight of current heifers was heavier than that of historic heifers. There were also a greater percentage of the current heifers at or above their target live weight compared with the historic heifers (P<0.001), suggesting that the rearing of dairy heifers has improved. The greatest improvement was seen at 15 months of age (mating) when 25\% of historic heifers were at or above target compared with 56\% of current heifers. Despite the improvement, 44\% of current heifers were below target at mating and 65\% were below target pre-calving (22 months of age). At 22 months of age, current heifers were on average nearly 42 kg below target live weight. By failing to achieve targets near calving, farmers are not capturing potential milk production benefits.}, issn = {1176-5283}, author = {Handcock RC and Lopdell TJ and McNaughton LR} } @conference {3672, title = {BRIEF COMMUNICATION: Birth weight of calves born to dairy cows in New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {75}, year = {2015}, month = {07/2015}, pages = {257-259}, address = {Dunedin}, abstract = { }, issn = {1176-5283}, author = {Hickson RE and Zhang IL and McNaughton LR} } @conference {89225, title = {Comparison of mating start date definitions for New Zealand dairy farms}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {79-82}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

If the mating start date (MSD) is incorrectly established through database monitoring, then several reproductive measures will also be incorrect in a seasonal calving dairy herd. The definition currently used by the InCalf Fertility Focus report is the first day withartificial breeding (AB) record(s) within a sequence of four of seven days with artificial breeding (AB) records (Method A). The objective was to compare this with alternative definitions to reduce the occasional incidence of incorrect MSD that have been encountered in these reports. The alternative definitions testedwere two consecutive and four out of seven days (Method B), one percent (Method C) and three consecutive days (Method D). The National Dairy Database was used to test these alternate definitions. Among 963 herds with less than 150 cows, the current definition of MSD was the most appropriate. Among 7,004 herds with greater than or equal to 150 cows, visual assessment indicated that a new definition was more accurate. This was that MSD be set as the first of two consecutive days when followed with four of the next seven days having recorded AB matings.

}, issn = {1176-5283}, author = {Creagh FE and Sanders K and McNaughton LR} } @conference {89232, title = {Effect of heifer live weight on calving pattern and milk production}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {103-107}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

Many heifers on New Zealand dairy farms fail to reach their target live weight. This failure leads to lost milk production and poorer reproductive performance. This study investigated effects of breed and region on heifer live weight and also effects of pre-calving heifer live weight (18{\textendash}21 months) on milk production. Less Friesian heifers reached their target live weight than Jerseys, or Crossbreds (85.3 versus 89.3 versus 88.1\%; P \<0.001). Heifers born in Otago (91.9\%) and Taranaki (91.8\%) were the closest to achieving their target live weight, whilst those born on the West Coast (85.6\%) and Northland (86.0\%) had the greatest number of heifers not reaching their target. Heifers that had only one calving recorded on the database were a significantly lower percentage of target live weight than those heifers that had two calvings recorded (83.5\% versus 87.1\%; P \<0.001). In heifers with a live weight record between 18 and 21 months of age, every 1\% increase in the percentage of target live weight attainedwas associated with an increase in milk volume of 23 {\textpm} 0.6 litres in the first lactation and 24 {\textpm} 0.9 litres inthe second lactation. Further work is required on the economics of feeding heifers to achieve their target live weight.

}, issn = {1176-5283}, author = {McNaughton LR and Lopdell T} } @conference {89235, title = {Insulin response to a glucose tolerance test in 18-month pregnant heifers as a predictor of subsequent survival}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {73}, year = {2013}, month = {Jan}, pages = {117-119}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {

A decline in dairy cow fertility in the USA and in the UK (Beam \& Butler 1999; Royal et al. 2000) has also been noted in New Zealand. Calving rate, the proportion of cows re-calving within the first 42 days of the subsequent seasonal calving period, in New Zealand decreased from approximately 70\% in 1991 to 60\% in 2004 (Harris et al. 2006). There has been no further deterioration in subsequent years.

}, issn = {1176-5283}, author = {Hutchinson KJ and Davis SR and MacKenzie DDS and Blair HT and McNaughton LR and Sanders K and Spelman RJ} } @conference {78999, title = {Are dairy heifers achieving liveweight targets?}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {120-122}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The reproductive performance of the national dairy herd has declined (Harris et al. 2006). Heifer rearing is one of eight "ingredients" for achieving good reproductive performance identified by the InCalf project (Burke et al. 2007). Many New Zealand dairy farmers graze their heifers on a run-off or pay a grazier to grow the heifers, with heifers commonly leaving the dairy farm at weaning, or nine months of age and returning at around 22 months of age.}, issn = {1176-5283}, author = {McNaughton LR and Lopdell TJ} } @conference {41762, title = {The genetic relationship between heifer and cow fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {388-391}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Initial predictors of dairy bulls{\textquoteright} fertility proofs are currently limited to body condition score (BCS), milk yield and success of mating in the first 21 days (PM21) for their two-year-old lactating daughters. The first calving rate trait (CR42) is available after a cow has calved for a second time. Obtaining an earlier indication of fertility would be useful for genetic evaluation purposes. The aim of this study was to investigate the genetic and phenotypic control of heifer fertility in addition to investigating the relationship between heifer fertility and traits already included in the prediction ofthe fertility breeding value. Data were available on LIC{\textquoteright}s Sire Proving Scheme animals born from 1989 to 2003 and included records on 244,453 animals. Using data on the first calving, planned start of calving was defined as the day within contemporary group when greater than 10\% of animals had calved. A multivariategenetic analysis was undertaken with the traits PM21, CR42, BCS and 270-day milk yield recorded in lactating cows, in addition to a heifer fertility trait where success is defined as heifers that calve within21 days from the planned start of calving (CR21). The model fitted to these traits included contemporary group of the milking herd, breed proportions and age at first calving as linear and quadratic effects. The mean CR21 in this dataset was 71\%. Heifers failing to calve within 21 days of the herd{\textquoteright}s planned start of calving for heifers also had poorer fertility in first lactation, with a least-squares-mean of 75.5\% (s.e. 0.2) versus 81.5\% (0.1) for PM21 and 54.2\% (0.22) and 62.4\% (0.1) for CR42. The heritability estimate of CR21 was low (0.012), yet the genetic variation was comparable to other fertility measures. CR21 had a positive genetic correlation with CR42, indicating that CR21 may be a useful early indicator of fertility for use in genetic evaluations.}, issn = {1176-5283}, author = {Pryce JE and Harris BL and McNaughton LR} } @conference {41714, title = {Hair whorl patterns are related to age at puberty and milk-production traits in dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {130-135}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {The objective of this study was to measure facial hair whorl characteristics of Friesian-Jersey crossbred cows (n=658) and to investigate their association withmeasures of milk production, fertility and behaviour. Cows had 1 (n=581), 2 (n=10), 3 (n=1) or no facial hair whorls (n=66). Of those cows with one whorl, 66\% had whorls in the middle of the head, whereas 21\% had whorls low on their head and 13\% high on their forehead. Round whorls were present on 77\% of cows, while 23\% had non-round whorls. Fifty five percent of cows with round whorls were recorded as havinganticlockwise rotation and 16\% of cows as clockwise rotation. Cows with high hair whorlstended to reach puberty earlier on average than cows with lower whorls (P=0.07). Cows with higher non-round whorls also produced lower total milk and total solid yields, than cows with low whorls (P=0.01). No relationship was found between hair whorl characteristics and behaviour in this study.}, issn = {1176-5283}, author = {Young SK and McNaughton LR and Spelman RJ} } @conference {42015, title = {Metabolic feed efficiency - opportunities for selection in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {392-398}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {A literature review and simulation study is presented to investigate the potential role of metabolic feed efficiency in dairy cattle breeding programmes. Metabolic efficiency is generally calculated as the difference between actual feed intake and expected feed requirements and as a result is a residual term, hence it is often referred to as residual feed intake (RFI). There is evidence of genetic variation in RFI in poultry, sheep and beef cattle. Heritability estimates inbeef cattle are moderate (0.14 to 0.43). Heritability estimates in dairy cattle range from zero (no genetic variation) to moderate (0.38). RFI is positively genetically correlated with feed intake, so more efficient animals tend to eat less. Information is sparse, but suggests there is no genetic correlation between milk production and RFI. Genetic correlations between health and fertility traits and RFI in cattle have not been established, but evidence frommice and pigs suggests unfavourable correlations between RFI and fertility. Estimating the genetic relationships between RFI and health and fertility in dairy cattle is required. The identification of genetic markers that explain sizeable variation in RFI, or an easily measured correlated trait would be the preferred options to enable selection for RFI in dairy cattle, ideally breeding values for RFI would be estimated and included as part of a multiple-trait selection index.}, issn = {1176-5283}, author = {McNaughton LR and Pryce JE} } @conference {41850, title = {Factors affecting methane production in Friesian x Jersey dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {352-355}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Methane production was measured in 301, 3-year-old Friesian x Jersey dairy cows, during summer 2004 in stage one of a project to define phenotypes for quantitative trait loci (QTL) mapping and to investigate the relationships between CH4 and milk production. Animals were allocated into four groups and their methane production was measured during four days. Feed intake was estimated by the alkane technique and by prediction equations. Correlations between the alkane technique and prediction equations were all less than 0.37, but correlations amongst the prediction equations were greater than 0.61. Daily CH4 output varied from 210 to 498 g and averaged 332 g. Dry matter intake averaged 19.3 g/kg DM. Milk production and live weight gain were negatively related to CH4 production per kg dry matter intake. Sire was not found to have a significant effect on CH4 output per kg of dry matter; however, only six sires are represented in the trial. The CH4 output recorded in the current study was within the ranges observed in other studies and was repeatable between days. High quality data were generated for the QTL study. KEYWORDS: methane; herbage intake; alkanes; dairy cows. }, issn = {1176-5283}, author = {McNaughton LR and Berry DP and Clark H and PinaresPatino C and Harcourt S and Spelman RJ} } @conference {41484, title = {Influence of material and sire effects on antibody response following clostridial vaccination of Friesian-Jersey crossbred calves}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {110-114}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {As part of an ongoing project to identify quantitative trait loci (QTL) for economically important traits in New Zealand dairy cows, a vaccine trial was conducted to measure the antibody response of 10 week old Friesian-Jersey crossbred calves to two antigenic compounds of a clostridial vaccine (Clostridium novyi B and Clostridium tetani toxoids). Blood samples were collected from 469 calves prior to vaccination at 10 weeks of age, prior to re-vaccination at 13 weeks of age and at 16 and 22 weeks of age. ELISA assays using conjugated rabbit anti-bovine IgG were conducted for both toxoids. Correlations and explanatory variables were calculated using correlation and general linear model (GLM) procedures in SAS. Antibody response to both toxins were relatively low after the first vaccination (week 13), but were boosted to high levels after revaccination (week 16). GLM analysis revealed a moderate sire effect contributing to the variability seen in the 13 week test against C. tetani (P=0.001) and the 16 week test against C. novyi (P=0.01). This variation in individual antibody response will be used in future research to identify genetic factors controlling the acquisition of immunity. }, issn = {1176-5283}, author = {Harcourt SJ and Buddle BM and Hamel K and McNaughton LR and Spelman RJ} } @conference {41486, title = {Use of breeding values for live weight to calculate individual live weight targets for dairy heifers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {118-121}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Replacement heifers need to reach specific target live weights (LW) to ensure they calve as two year olds, and subsequently achieve high milk yields and good fertility. Currently, different LW targets are recommended for heifers based on their expected mature LW according to appearance or breed. However, the mature LW is difficult to estimate without knowledge of the animals. genetic potential for LW. The objective of this paper is to develop and validate a growth model which uses estimated breeding values for LW (EBV LW) of individual heifers of any breed to calculate target LW from birth to maturity. Predicted live weights are presented for a range of four EBV LW, from {\textendash}40 to 100 kg. These values were very similar to other published target values. Data from the Dexcel Holstein Friesian Strain Trial was used to validate the model with respect to LW and age at puberty. For LW at puberty the predicted values were significantly correlated (P<0.05), but were marginally higher (3-5\%) than the actual values. A report can be formulated to enable farmers to identify individual heifers which are below (or above) their target LW at any date }, issn = {1176-5283}, author = {Bryant JR and Holmes CW and Lopez-Villalobos N and McNaughton LR and Brookes IM and Verkerk GA and Pryce JE} } @conference {41410, title = {Postpartum anoestrous intervals and reproductive performance of three genotypes of Holstein-Friesian dairy cattle managed in a seasonal pasture-based dairy system.}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {77-81}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {An extended postpartum anovulatory interval (PPAI) is the major form of infertility in New Zealand (NZ) dairy cattle. Recently, Holstein cows, originating from North American genetic strains (Overseas; OS), have been widely used in NZ. Worldwide, there is concern over an apparent decline in the fertility of Holstein-Friesian dairy cattle. This study determined whether differences existed in PPAI, BCS and parameters of reproductive performance between NZ and OS Holstein-Friesians. One hundred and forty-six records from 88 NZ animals of high genetic merit for milk production (NZH), 81 records from 48 NZ animals of low genetic merit (NZL), and 137 records from 88 OS high genetic merit animals that calved in Years 1 (all two-year-olds) and 2 (two- and three-year-olds) were included. Over both years PPAI in two-year-olds were significantly shorter in OS (20 days shorter) and NZL (12 days shorter) than in NZH animals (P<0.05). Body condition score at calving, and BCS loss from calving to four weeks postpartum were not different between strains. In Year 1 of the study significantly more NZH than NZL or OS 2-year-olds were treated for anoestrus prior to the start of mating (P=0.001). Other measures of reproductive performance did not differ significantly between strains. The differences in PPAI require further investigation. }, issn = {1176-5283}, author = {McNaughton LR and Verkerk GA and Parkinson TJ and MacDonald KA and Holmes CW} } @conference {41307, title = {Monitoring onset of puberty in three genetic strains of Holstein-Friesian dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {30-33}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {Live weight and age at puberty were determined in three strains of Holstein-Friesian dairy cattle in each of two consecutive years. The strains were overseas-origin high-breeding-worth genetics (OS), New Zealand-origin high-breeding-worth genetics (NZH), and New Zealand-origin low-breeding-worth genetics (NZL), similar to the New Zealand dairy cow of the 1970s. Onset of puberty was monitored by weekly measurement of progesterone in a total of 271 heifers. Animals were considered to have attained puberty when plasma progesterone concentrations were greater than 2ng/ml in two out of three consecutive samples. Live weight at puberty differed between the strains (OS > NZH > NZL; P<0.05) but not between years. Age at puberty was affected by strain in Year 1 (OS > NZH > NZL; P<0.01), but not in Year 2. The greater live weight required to attain puberty in OS genotype animals must be recognized in target live weights for rearing of heifers. }, issn = {1176-5283}, author = {McNaughton LR and Morgan SR and Gore P and Verkerk GA and Holmes CW and Parkinson TJ} }