Bishopton Veterinary Group, Mill Farm, Ripon, North Yorkshire, United Kingdom.
Department of Livestock Health and Welfare, Institute of Veterinary Science, University of Liverpool, Leahurst Campus, Neston, Wirral, United Kingdom.
PLoS One. 2018 Jun 13;13(6):e0197764. doi: 10.1371/journal.pone.0197764. eCollection 2018.
Lactation records from 396,534 pedigree Holstein and Holstein-Friesian primiparous cows from 6,985 UK milk recorded herds, calving for the first time during the period between the 1st of January 2006 and the 31st of December 2008, were examined in order to determine the associations between age at first calving (AFC) and subsequent production, udder health, fertility and survivability parameters. Heifers were grouped by AFC into single month classes ranging from 21 to 42 months. Mixed effects multivariable regression modelling was used for data analysis. Mean and median AFC were 29.1 and 28 months respectively. Within the study, only 48,567 heifers (12.3% of the studied population) calved for the first time at 24 months of age or younger. 162,157 heifers (40.9%) were 30 months or older at their first calving. An increased AFC was associated with increased first lactation milk, fat and protein yields. The lowest predicted mean 305-day yield (6,617kgs; 95% confidence interval (CI): 6,546-6,687 kgs) was recorded for the 21 month AFC class, significantly lower than any other class. The 36 month AFC class had the highest predicted mean (7,774 kgs; 95% CI: 7,737-7,811 kgs). However, an increased AFC was also associated with increased calving interval and increased first lactation somatic cell count (SCC). Animals calving at 21 months had a predicted mean lactation SCC of 72,765 (95% CI: 68427-77378). Animals calving at 36 months of age had a predicted mean lactation SCC of 86,648 (95% CI: 84,499-88,853). Importantly, an increased AFC was also associated with decreased lifetime daily milk yield and decreased likelihood of calving for a second successive time. Animals calving at 22 months of age had a predicted mean daily lifetime milk yield of 15.24 kgs (95% CI: 15.06-15.35); animals calving at 36 months of age had a predicted mean daily lifetime milk yield of 12.83 kgs (95% CI: 12.76-12.91). Our results highlight the importance of achieving a lower age at first calving which was here associated with improved udder health, increased lifetime daily milk yield, improved reproductive performance and increased likelihood of calving for a second time.
本研究旨在探讨首次产犊年龄（AFC）与随后的生产性能、乳房健康、繁殖力和存活率参数之间的关系。为此，我们分析了来自英国 6985 个牛奶记录牛群的 396534 头纯种荷斯坦和荷斯坦-弗里生初产母牛的数据，这些母牛于 2006 年 1 月 1 日至 2008 年 12 月 31 日期间首次产犊。这些牛群中的小母牛按照 AFC 分为 21 至 42 个月的单月组。采用混合效应多变量回归模型进行数据分析。平均和中位数 AFC 分别为 29.1 和 28 个月。在本研究中，只有 48567 头（研究人群的 12.3%）小母牛在 24 个月龄或更小时首次产犊。162157 头（40.9%）小母牛在首次产犊时年龄为 30 个月或更大。AFC 增加与首次泌乳奶量、脂肪和蛋白质产量增加有关。预测平均 305 天产奶量最低的是 21 月龄 AFC 组（6617 公斤；95%置信区间（CI）：6546-6687 公斤），明显低于其他任何组。36 月龄 AFC 组的预测平均产奶量最高（7774 公斤；95%CI：7737-7771 公斤）。然而，AFC 增加也与产犊间隔和首次泌乳体细胞数（SCC）增加有关。21 月龄产犊的动物的预测平均泌乳 SCC 为 72765（95%CI：68427-77378）。36 月龄产犊的动物的预测平均泌乳 SCC 为 86648（95%CI：84499-88853）。重要的是，AFC 增加也与终生日产量降低和连续第二次产犊的可能性降低有关。22 月龄产犊的动物的预测平均终生日产量为 15.24 公斤（95%CI：15.06-15.35）；36 月龄产犊的动物的预测平均终生日产量为 12.83 公斤（95%CI：12.76-12.91）。我们的研究结果强调了实现首次产犊年龄降低的重要性，因为这与乳房健康改善、终生日产量增加、繁殖性能提高和连续第二次产犊的可能性增加有关。
