School of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
LIC, Hamilton, New Zealand.
N Z Vet J. 2020 Sep;68(5):272-282. doi: 10.1080/00480169.2020.1750498. Epub 2020 May 25.
To examine the relationship between liveweight (LWT) at 12 months as a proportion of LWT at 21 months of age (LWT(12/21)%) and first lactation and cumulative 3-year milk production in dairy heifers in New Zealand. Liveweight and milk production records were obtained for dairy heifers born from June to December (spring-calving season) between 2006-2007 and 2013-2014 dairy seasons; production records included first lactation (n = 140,113) and cumulative 3-year (n = 67,833) milksolids and energy-corrected milk (ECM) yields. Heifers were classified into five breed groups; Holstein-Friesian, Holstein-Friesian crossbred, Jersey, Jersey crossbred and Holstein-Friesian-Jersey crossbred. Within each breed group heifers were categorised into quintiles based on 21-month LWT. The LWT(12/21)% was calculated for each animal. Relationships between LWT(12/21)% and milk production within each breed group and LWT category were estimated using linear mixed effects models including the linear and quadratic effects of LWT(12/21)%. The relationship between LWT(12/21)% and milk production was predominantly curvilinear, with lower milk production at lesser LWT(12/21)% compared with greater LWT(12/21)%. For all breed groups and most LWT categories, heifers that were 55 or 65% LWT(12/21)% produced greater ECM and milksolids yields compared with heifers that were 45% LWT(12/21)%. Holstein-Friesian, Holstein-Friesian crossbred and Holstein-Friesian-Jersey crossbred heifers that were 65% LWT(12/21)% produced greater cumulative 3-year ECM and milksolids yields compared with heifers of the same breed group that were 45% LWT(12/21)% Heifers that were a greater proportion of their 21-month LWT at 12 months of age produced more first lactation and cumulative 3-year milk yields than heifers that were a lesser proportion of their 21-month LWT at 12 months of age. These results indicate that increased growth in early life of New Zealand dairy heifers is beneficial to future milk production.
为了研究新西兰奶牛小母牛在 12 月龄时的体重（LWT）占 21 月龄 LWT 的百分比（LWT（12/21）%）与初乳和累积 3 年牛奶产量之间的关系。我们获得了 2006-2007 年和 2013-2014 年奶牛季节中 6 月至 12 月（春季产犊季节）出生的奶牛小母牛的体重和产奶记录；生产记录包括初乳（n=140113）和累积 3 年（n=67833）乳固体和能量校正乳（ECM）产量。小母牛分为五个品种组；荷斯坦-弗里生、荷斯坦-弗里生杂交、泽西、泽西杂交和荷斯坦-弗里生-泽西杂交。在每个品种组内，根据 21 月龄 LWT 将小母牛分为五组。为每只动物计算 LWT（12/21）%。使用线性混合效应模型，包括 LWT（12/21）%的线性和二次效应，估计每个品种组和 LWT 类别内 LWT（12/21）%与产奶量之间的关系。LWT（12/21）%与产奶量的关系主要是曲线关系，与较大的 LWT（12/21）%相比，较小的 LWT（12/21）%产奶量较低。对于所有品种组和大多数 LWT 类别，55%或 65%LWT（12/21）%的 ECM 和乳固体产量大于 45%LWT（12/21）%的小母牛。65%LWT（12/21）%的荷斯坦-弗里生、荷斯坦-弗里生杂交和荷斯坦-弗里生-泽西杂交小母牛比同品种组 45%LWT（12/21）%的小母牛产生更多的累积 3 年 ECM 和乳固体产量。12 月龄时体重占 21 月龄体重比例较大的小母牛比 12 月龄时体重占 21 月龄体重比例较小的小母牛，初乳和累积 3 年牛奶产量更高。这些结果表明，新西兰奶牛小母牛在生命早期的生长增加有利于未来的牛奶产量。
