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J Dairy Sci. 2022 Sep;105(9):7513-7524. doi: 10.3168/jds.2022-21847. Epub 2022 Jul 22.
Adjusting end-of-milking criteria, in particular applying a maximum milking time determined by expected milk yield at an individual milking session, is one strategy to optimize parlor efficiency. However, this strategy can be difficult to apply practically on farm due to large differences in session milk yield, driven by milking interval, which affects milking routines and can be limited by in-parlor technology. The objective of this study was to test the hypothesis that a single fixed milking time (duration) could be applied at all milking sessions without compromising milk production or udder health for a range of milking intervals. To test the hypothesis, 4 experimental herds were established: (1) herd milked twice a day (TAD) using a 10- and 14-h interval, (2) herd milked TAD using an 8- and 16-h interval, (3) herd milked 3 times in 2 d using a 10-19-19-h interval, and (4) herd milked once a day (OAD). Herds consisted of 40 cows each, and were established for two 6-wk experimental periods, one in peak lactation and the other in mid-late lactation. Within each herd, half the cows had an end-of-milking criterion of 0.35 kg/min (Flow), and the other half had milking ended after a fixed period of time (FixedT) based on the average milking session yield, the daily milk yield divided by average number of milkings per day, irrespective of milking interval. We found no differences in daily milk yield between end-of-milking criteria due to residual milk from one milking likely increasing the proportion of milk in the udder cistern at the next milking session for the FixedT treatment. However, fat yield was compromised when the percentage of the herd with a truncated milking exceeded an estimated 33% at a milking session, which occurred in the TAD 8-16 herd due to the divergence from the average milking interval (in the case of TAD, 12-12 h). Applying a fixed milking time had no detrimental effects on udder health, except in the OAD herd in mid-late lactation, which had both a higher cell count and new intramammary infection rate. This warrants further investigation, although the majority of cultured bacteria were coagulase-negative staphylococci (CNS). Consequently, we conclude that, in general, with appropriate monitoring (e.g., weekly inspection) to ensure the proportion of the herd with truncated milkings does not exceed 33%, farmers in pasture-based dairy systems can use a fixed milking time to improve parlor efficiency.
调整挤奶结束标准，特别是应用由单次挤奶预计产量决定的最大挤奶时间，是优化牛舍效率的一种策略。然而，由于挤奶间隔导致的单次挤奶产量存在较大差异，这种策略在实际农场中难以实施，这会影响挤奶程序，且可能受到牛舍内技术的限制。本研究旨在检验以下假设，即在不同挤奶间隔下，所有挤奶阶段应用单一固定挤奶时间（时长）而不影响产奶量或乳房健康。为了检验该假设，建立了 4 个实验牛群：（1）采用 10-14 小时和 8-16 小时两种挤奶间隔的每日挤奶两次（TAD）牛群；（2）采用 10-19-19 小时的三日内挤奶三次的 TAD 牛群；（3）每日挤奶一次（OAD）牛群；（4）采用 TAD 挤奶且间隔为 10-14 小时的牛群。每个牛群由 40 头牛组成，进行了两个为期 6 周的实验阶段，一个在泌乳高峰期，另一个在泌乳中期和后期。在每个牛群中，一半奶牛采用 0.35kg/min（流量）的挤奶结束标准，另一半奶牛采用固定时间（FixedT）的挤奶结束标准，该标准基于单次挤奶产量，即日产奶量除以每日平均挤奶次数，而不考虑挤奶间隔。我们发现，由于单次挤奶结束时残留的牛奶可能在下一次挤奶时增加乳房蓄奶池内的牛奶比例，因此基于固定时间的挤奶结束标准导致的产奶量差异并不明显。然而，当采用固定时间结束挤奶的奶牛比例估计超过 33%时，脂肪产量会受到影响，这种情况出现在 TAD 8-16 小时牛群中，因为该牛群的挤奶间隔与平均值相差较大（在 TAD 牛群中，间隔为 12-12 小时）。应用固定挤奶时间对乳房健康没有不利影响，除了在泌乳中期和后期的 OAD 牛群中，该牛群的体细胞计数和新的乳腺炎感染率较高。这需要进一步研究，尽管大多数培养细菌是凝固酶阴性葡萄球菌（CNS）。因此，我们得出结论，一般来说，在牧场奶牛系统中，农民可以采用固定的挤奶时间来提高牛舍效率，只要适当监测（例如每周检查）以确保采用固定时间结束挤奶的奶牛比例不超过 33%。
