1Department of Reproduction,Obstetrics and Herd Health, Faculty of Veterinary Medicine,Ghent University,Salisburylaan 133,9820 Merelbeke,Belgium.
2Department of Animal Sciences,Institute for Agricultural and Fisheries Research (ILVO),Scheldeweg 68,9090 Melle,Belgium.
Animal. 2017 Dec;11(12):2252-2259. doi: 10.1017/S1751731117001021. Epub 2017 May 24.
The aim of the present research was to assess factors associated with first-lactation milk yield in dairy heifers, including maternal and environmental factors, factors related to the development of the heifer and factors related to its offspring such as gender of the calf. In addition, the potential underlying mechanism, in particular metabolic adaptations, was further explored. Data on body growth, reproduction and milk yield of 74 Holstein Friesian heifers on three herds in Flanders (Belgium) were collected. At birth, body measurements of the heifers were recorded and blood samples were taken (in order) to determine basal glucose and insulin concentrations. Body measurements were assessed every 3 months until first calving, and gender and weight of their first calf were recorded. Information on fertility and milk yield of the heifer and its dam were collected from the herd databases. Daily temperature and photoperiod were recorded from the database of the Belgian Royal Meteorological Institute. Linear mixed models were run with herd as a random factor, to account for differences in herd management. Heifers grew 867±80.7 g/day during their first year of life and were inseminated at 14.8±1.34 months. First calving took place at 24.5±1.93 months, at a weight of 642±61.5 kg and heifers produced 8506±1064 kg energy corrected milk during their first 305-day lactation. Regression models revealed that none of the maternal factors such as milk yield and parity, nor the growth of the heifer during the 1st year of life were associated with milk yield during first lactation. Age, and to a lesser extent BW at first parturition were positively associated with first-lactation milk yield. In addition, the season of birth, but not calving, had a significant influence on milk yield, with winter-born heifers producing less than heifers born in any other season. The lower yielding winter-born heifers had higher insulin concentrations at birth, whereas glucose concentrations were similar, the latter being suggestive for lower insulin sensitivity of the peripheral tissues. Furthermore, environmental temperature at the end of gestation was negatively correlated with neonatal insulin concentrations. In conclusion, results of the present study suggest heifers born during the hotter months are born with a higher peripheral insulin sensitivity, finally leading to a higher first-lactation milk yield.
本研究旨在评估与奶牛初乳产奶量相关的因素，包括母体和环境因素、与奶牛生长发育相关的因素以及与后代相关的因素，如犊牛性别。此外，还进一步探讨了潜在的机制，特别是代谢适应。在比利时佛兰德斯的三个牛群中收集了 74 头荷斯坦弗里生奶牛的体生长、繁殖和产奶量数据。在出生时，记录了奶牛的体尺，并采集了血液样本（按顺序）以确定基础葡萄糖和胰岛素浓度。在第一次产犊前，每 3 个月评估一次体尺，记录第一头犊牛的性别和体重。从牛群数据库中收集了奶牛及其母亲的产奶量和繁殖力信息。从比利时皇家气象研究所的数据库中记录了每日温度和光照周期。使用牛群作为随机因素进行线性混合模型分析，以解释牛群管理的差异。奶牛在其生命的第一年中每天生长 867±80.7 克，在 14.8±1.34 月龄时进行配种。第一次产犊发生在 24.5±1.93 月龄，体重为 642±61.5 千克，在其第一次 305 天泌乳期内生产了 8506±1064 千克能量校正奶。回归模型显示，母体因素（如产奶量和胎次）以及奶牛在第一年的生长情况均与初乳产奶量无关。年龄，以及较小程度上第一次分娩时的体重，与初乳产奶量呈正相关。此外，出生季节而不是分娩季节对产奶量有显著影响，冬季出生的奶牛产奶量低于其他季节出生的奶牛。产奶量较低的冬季出生的奶牛出生时胰岛素浓度较高，而葡萄糖浓度相似，这表明外周组织的胰岛素敏感性较低。此外，妊娠末期的环境温度与新生儿胰岛素浓度呈负相关。总之，本研究结果表明，在较热的月份出生的奶牛具有更高的外周胰岛素敏感性，最终导致初乳产奶量更高。
