Département de pathologie et microbiologie, Université de Montréal, 3200 Rue Sicotte, St-Hyacinthe, Québec, J2S 2M2, Canada.
Département de sciences cliniques, Faculté de médecine vétérinaire, Université de Montréal, 3200 Rue Sicotte, St-Hyacinthe, Québec, J2S 2M2, Canada.
J Dairy Sci. 2018 May;101(5):4367-4377. doi: 10.3168/jds.2017-14021. Epub 2018 Feb 22.
An incomplete milking in early lactation could help limit negative energy balance in dairy cattle, but its potential effects on culling hazard and on milk production and composition throughout the entire lactation are unknown. The objective of this study was to evaluate the effect of an incomplete milking during the first 5 d in milk on culling hazard, milk weight, milk fat and protein concentrations, and energy-corrected milk (ECM) yield during the whole lactation. A randomized controlled trial was conducted in 13 dairy farms near St-Hyacinthe, Quebec, Canada. Approximately 1 mo before expected calving, Holstein multiparous cows calving between December 2013 and March 2015 (n = 846 cow lactations) were randomly assigned to a control or a treatment group. Cows in the control group were milked conventionally, whereas cows in the treatment group were submitted to an incomplete milking protocol (maximum of 10, 12, and 14 L/d of milk was collected on days in milk 1-3, 4, and 5, respectively). All farms were registered on Dairy Herd Improvement Association, which was used to obtain records on culling, monthly milk yield, and milk fat and protein concentrations. In addition, daily milk yield records were available for 6 farms. A Cox proportional hazards model with a herd frailty term was fitted to the data to compare culling hazard among treatment groups. Regarding milk production and composition, 4 linear mixed models with herd as a fixed effect, cow as a random effect, and using an autoregressive covariance structure were used to study the effect of the incomplete milking on (1) milk weight, (2) milk fat concentration, (3) milk protein concentration, and (4) ECM yield. Culling hazard did not differ among treatment groups (hazard ratio = 1.0; 95% CI = 0.82, 1.3). We observed no differences in milk weight, milk fat, or protein concentration among treatment groups between weeks in milk (WIM) 2 and 44 (the studied period). We noted a difference in ECM between treatment groups for WIM 38, with incompletely milked cows producing less milk than conventionally milked cows (-2.7 kg/d; 95% CI = -0.02, -5.2 kg/d), but no differences were found for any of the other WIM. These results suggest that this strategy for controlling the negative energy balance has negligible effect on cow productivity.
在泌乳早期进行不完全挤奶可以帮助限制奶牛的负能平衡，但它对淘汰风险以及整个泌乳期的产奶量和成分的潜在影响尚不清楚。本研究的目的是评估在泌乳第 1-5 天进行不完全挤奶对淘汰风险、奶量、乳脂和乳蛋白浓度以及整个泌乳期的能量校正奶（ECM）产量的影响。在加拿大魁北克省圣 Hyacinthe 附近的 13 个奶牛场进行了一项随机对照试验。大约在预计分娩前 1 个月，2013 年 12 月至 2015 年 3 月之间分娩的荷斯坦经产奶牛（n = 846 个泌乳期）被随机分配到对照组或处理组。对照组的奶牛进行常规挤奶，而处理组的奶牛则接受不完全挤奶方案（第 1-3 天、第 4 天和第 5 天每天分别采集最多 10、12 和 14 L 的牛奶）。所有农场都在奶牛改良协会注册，该协会用于获得淘汰记录、每月产奶量以及乳脂和乳蛋白浓度记录。此外，有 6 个农场提供了每日产奶量记录。使用 herd 脆弱性项拟合 Cox 比例风险模型来比较处理组之间的淘汰风险。关于产奶量和成分，使用 4 个线性混合模型，以 herd 为固定效应，以 cow 为随机效应，并使用自回归协方差结构，研究不完全挤奶对（1）奶量、（2）乳脂浓度、（3）乳蛋白浓度和（4）ECM 产量的影响。处理组之间的淘汰风险没有差异（风险比=1.0；95%CI=0.82，1.3）。我们在 WIM 2 和 44 之间的处理组之间没有观察到奶量、乳脂或乳蛋白浓度的差异（研究期间）。我们注意到在 WIM 38 时，处理组之间的 ECM 存在差异，不完全挤奶的奶牛比常规挤奶的奶牛少产奶（-2.7 kg/d；95%CI=-0.02，-5.2 kg/d），但在任何其他 WIM 时都没有差异。这些结果表明，这种控制负能平衡的策略对奶牛生产力的影响可以忽略不计。
