Department of Dairy Science, University of Wisconsin-Madison, Madison, WI.
Department of Animal Science, University of Zagreb, Zagreb, Croatia.
J Anim Sci. 2019 May 30;97(6):2424-2432. doi: 10.1093/jas/skz113.
Increased milking frequency and incomplete milking have differential effects on milk yield and mammary gland physiology that are important for optimization of milking practices in dairy herds. The objectives of this experiment were to determine the effects of increased milking frequency and incomplete milking on milk production rate (MPR) and milk composition and to determine if milking 3 times daily (3×) could rescue the negative production effects of incomplete milking. Twenty-two multiparous cows were enrolled onto this experiment beginning at 5 days in milk (DIM) and continuing through 47 DIM. A split-plot design was used to randomize the 2 treatments, which were milking frequency and incomplete milking. Eleven cows were randomly assigned to be milked 2 times (2×) daily and 11 cows were randomly assigned to be milked 3×. Within each cow, a contralateral half-udder was randomly assigned to be incompletely milked (30% milk remaining in the gland; IM), and the other half-udder was randomly assigned to be milked completely (CM). Quarter-level milk yields were recorded at each milking session. Milk samples from all quarters were collected twice weekly at the beginning of the morning milking for analysis. Cows milked 2× tended to have reduced MPR compared with 3× milked cows (1.81 ± 0.06 vs. 1.97 ± 0.06 kg milk/h; P = 0.06). Half-udders that were CM and IM produced 1.09 ± 0.03 and 0.80 ± 0.03 kg milk/h, respectively. There was an interaction between incomplete milking treatment and week of lactation (P = 0.04). No interaction was detected between milking frequency and incomplete milking for MPR or milk components. Cows milked 3× had increased milk fat percent (1.93 ± 0.09% vs. 1.65 ± 0.09%, P = 0.047), decreased milk lactose percent (4.80 ± 0.04% vs. 4.93 ± 0.04%, P = 0.04), and exhibited no differences in milk protein percent or milk somatic cell count (SCC) compared with cows milked 2×. Half-udders that were IM had increased milk fat percent (2.15 ± 0.07% vs. 1.43 ± 0.07%, P < 0.0001), decreased lactose percent (4.75 ± 0.03% vs. 4.99 ± 0.03%, P < 0.0001), increased milk log10SCC (4.22 ± 0.05 vs. 4.41 ± 0.05, P = 0.0004), and no differences in milk protein percent compared with CM half-udders. These results indicate that a 3× milking frequency in IM half-udders was not able to improve milk production compared with IM half-udders milked 2×. Our results indicate that 30% milk remaining in the gland had an irreversible impact on milk yield as increased milking frequency was not able to reverse the milk yield lost.
增加挤奶频率和不完全挤奶对产奶量和乳腺生理学有不同的影响，这对优化奶牛场的挤奶实践很重要。本实验的目的是确定增加挤奶频率和不完全挤奶对产奶率（MPR）和牛奶成分的影响，并确定每天挤奶 3 次（3×）是否可以挽救不完全挤奶的负面生产影响。22 头经产奶牛从产犊后 5 天（DIM）开始参与本实验，持续到 47 DIM。采用裂区设计随机分配 2 种处理，即挤奶频率和不完全挤奶。11 头奶牛随机分配每天挤奶 2 次（2×），11 头奶牛随机分配每天挤奶 3 次（3×）。在每头奶牛中，对侧半乳随机分配不完全挤奶（乳腺中残留 30%的牛奶；IM），另一半乳随机分配完全挤奶（CM）。每次挤奶时记录 quarters 级别的产奶量。在早晨挤奶开始时每周两次收集所有 quarters 的牛奶样本进行分析。与 3×挤奶的奶牛相比，2×挤奶的奶牛的 MPR 趋于降低（1.81 ± 0.06 vs. 1.97 ± 0.06 kg 牛奶/h；P = 0.06）。CM 和 IM 的半乳分别产生 1.09 ± 0.03 和 0.80 ± 0.03 kg 牛奶/h。不完全挤奶处理和泌乳周之间存在交互作用（P = 0.04）。未检测到挤奶频率和不完全挤奶对 MPR 或牛奶成分的相互作用。与 2×挤奶的奶牛相比，3×挤奶的奶牛的牛奶脂肪百分比增加（1.93 ± 0.09% vs. 1.65 ± 0.09%，P = 0.047），牛奶乳糖百分比降低（4.80 ± 0.04% vs. 4.93 ± 0.04%，P = 0.04），牛奶蛋白质百分比或牛奶体细胞计数（SCC）没有差异。与 CM 半乳相比，IM 的半乳牛奶脂肪百分比增加（2.15 ± 0.07% vs. 1.43 ± 0.07%，P < 0.0001），乳糖百分比降低（4.75 ± 0.03% vs. 4.99 ± 0.03%，P < 0.0001），牛奶 log10SCC 增加（4.22 ± 0.05 vs. 4.41 ± 0.05，P = 0.0004），但牛奶蛋白质百分比与 CM 半乳无差异。这些结果表明，在 IM 半乳中，3×挤奶频率不能提高产奶量，与 2×挤奶的 IM 半乳相比。我们的结果表明，乳腺中残留的 30%牛奶对产奶量有不可逆转的影响，因为增加挤奶频率并不能挽回失去的产奶量。
