Department of Ruminant Science, Institute of Animal Sciences, The Volcani Center, 68 HaMaccabim Road, Rishon LeZion 7505101, Israel.
Department of Ruminant Science, Institute of Animal Sciences, The Volcani Center, 68 HaMaccabim Road, Rishon LeZion 7505101, Israel; Department of Animal Science, the Robert H. Smith Faculty of Agriculture, Food and Environment, the Hebrew University of Jerusalem, Rehovot 76100, Israel.
J Dairy Sci. 2019 Oct;102(10):9468-9480. doi: 10.3168/jds.2019-16674. Epub 2019 Aug 7.
Reducing milk production during early lactation might be of interest to improve the energy balance (EB) of high-yielding dairy cows. Therefore, the objective of this study was to determine how reducing the milking frequency (MF) of high-yielding dairy cows from thrice to twice a day during the first 30 d in milk (DIM) affects yields, intake, efficiency, metabolic status, and carryover effects. To this end, 42 multiparous cows were divided into 2 groups according to their previous lactation performance, parity, and body weight. The control cows were milked 3 times a day (3ML) and the treated cows were milked twice a day (2ML) until 30 DIM and then both groups were milked 3 times a day. Milk samples were taken twice a week from 2 or 3 consecutive milkings until 45 DIM for analysis of milk solids, and both groups were followed until 100 DIM to determine the carryover effects of MF until 30 DIM. Individual dry matter intake (DMI), milk yield, and body weight were recorded daily. Blood samples were taken 3 times weekly from 14 d prepartum until 45 DIM. Milk yield during the first 30 DIM was 8.6% higher (49.3 and 45.4 kg/d, respectively), milk fat percentage was lower (3.96 and 4.27%, respectively), and the yields of all milk solids were higher in the 3ML cows than in the 2ML cows. Dry matter intake and 4% fat-corrected milk were similar between groups. The EB during the first 30 DIM was lower in the 3ML cows than in the 2ML cows, and milk yield, but not 4% fat-corrected milk yield, per unit of DMI was higher in the 3ML cows. No differences were observed between groups from 31 to 100 DIM in milk yield (∼56.3 kg/d for both groups), milk solids yield, DMI, or milk/DMI; however, fat percentage was lower and EB was higher in the 3ML cows. Blood glucose concentrations between 0 and 30 DIM were lower and β-hydroxybutyrate concentrations were higher in the 3ML cows than in the 2ML cows, but nonesterified fatty acids concentrations were lower, which may be attributed to the lower clearance frequency of nonesterified fatty acids from the blood stream in the 2ML cows. A lower proportion of the 3ML cows (10%) ovulated ≤15 DIM compared with the 2ML cows (40%), with no beneficial effects on preovulatory follicle characteristics. Reducing the MF from thrice to twice a day during the first 30 DIM improved EB and metabolic status, with only minor effects on production.
在泌乳早期减少牛奶产量可能有助于改善高产奶牛的能量平衡（EB）。因此，本研究的目的是确定在泌乳的前 30 天（DIM）内，将高产奶牛的挤奶频率（MF）从每天 3 次减少到每天 2 次，如何影响产奶量、采食量、效率、代谢状态和残留效应。为此，将 42 头经产奶牛根据其前一个泌乳期的表现、胎次和体重分为两组。对照组奶牛每天挤奶 3 次（3ML），处理组奶牛每天挤奶 2 次（2ML），直到 30 DIM，然后两组奶牛每天挤奶 3 次。从 2 或 3 次连续挤奶中每周采集 2 次奶样，直至 45 DIM 进行乳固体分析，两组奶牛均跟踪至 100 DIM，以确定 MF 对 30 DIM 的残留效应。每天记录个体干物质采食量（DMI）、产奶量和体重。从产前 14 天到 45 DIM，每周采集 3 次血样。在第 30 天 DIM 内，3ML 奶牛的产奶量增加了 8.6%（分别为 49.3 和 45.4 kg/d），乳脂率降低（分别为 3.96%和 4.27%），所有乳固体的产量都高于 2ML 奶牛。两组间的干物质采食量和 4%脂肪校正乳无差异。在第 30 天 DIM 内，3ML 奶牛的 EB 低于 2ML 奶牛，而 3ML 奶牛每单位 DMI 的产奶量和 4%脂肪校正乳产量更高。从第 31 天到第 100 天，两组的产奶量（两组均为约 56.3 kg/d）、乳固体产量、DMI 或乳/DMI 均无差异；然而，3ML 奶牛的乳脂率较低，EB 较高。3ML 奶牛的血糖浓度在 0 至 30 DIM 之间较低，β-羟丁酸浓度较高，而非酯化脂肪酸浓度较低，这可能归因于 2ML 奶牛血液中非酯化脂肪酸清除频率较低。与 2ML 奶牛（40%）相比，3ML 奶牛（10%）在 ≤15 DIM 时排卵的比例较低，对促黄体生成素前卵泡特征没有有益影响。在泌乳的前 30 天内，将 MF 从每天 3 次减少到每天 2 次，改善了 EB 和代谢状态，对生产仅有微小影响。
