Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853.
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 2020 Apr;103(4):3668-3682. doi: 10.3168/jds.2019-17342. Epub 2020 Jan 31.
The objectives were to study the effect of 2 different automatic cluster remover settings on (1) milking characteristics, (2) milk component yields, (3) teat tissue condition, and (4) udder health. In a randomized controlled field trial, Holstein cows (n = 689) from 1 commercial dairy farm with a thrice-daily milking schedule were allocated to 2 treatment groups. Treatment consisted of a cluster remover take-off milk flow threshold of 1.2 (ACR1.2) or 0.8 kg/min (ACR0.8) for 57 d. Milking characteristics (milk yield; and milking unit-on time, MUOT) were obtained with electronic on-farm milk meters. Composite milk samples were collected and analyzed for fat, protein, lactose, and somatic cell count. Machine-milking-induced short- and long-term changes to the teat tissue condition were assessed visually. General linear mixed models demonstrated differences in MUOT, whereas no meaningful differences in milk yield were detected. Milk yield (least squares means, 95% confidence interval) was 11.3 (10.9-11.8) and 11.3 (10.8-11.8) kg in groups ACR1.2 and ACR0.8, respectively. The effect of treatment on MUOT was modified by parity. Milking unit-on time in first-, second-, and ≥third-lactation cows, respectively, was 260.7 (252.0-269.4), 257.8 (247.4-268.1), and 260.2 (252.6-267.9) s in group ACR1.2; and 273.7 (264.9-282.5), 279.1 (269.4-288.8), and 295.7 (287.9-303.6) s in group ACR0.8. We detected no meaningful differences in milk component yields or linear somatic cell score. Least squares means in groups ACR1.2 and ACR0.8, respectively, were milk fat yield, 0.42 (0.40-0.44) and 0.42 (0.40-0.44) kg; milk protein yield, 0.36 (0.35-0.37) and 0.37 (0.36-0.37) kg; milk lactose yield, 0.61 (0.60-0.63) and 0.63 (0.61-0.64) kg, and linear somatic cell score, 1.9 (1.8-2.0) and 1.9 (1.8-2.0). A generalized linear mixed model revealed an effect of treatment on machine-milking-induced short-term changes. The odds of short-term changes to the teat tissue were lower for cows in group ACR1.2 [odds ratio (95% confidence interval) = 0.78 (0.63-0.96)]. No meaningful differences were detected in machine-milking-induced long-term changes between treatment groups. Increasing cluster remover take-off milk flow threshold from 0.8 to 1.2 kg/min decreased individual milking duration and alleviated machine-milking-induced short-term changes to the teat tissue without adversely affecting milking performance or somatic cell count. Future studies are warranted to investigate the effect on milk production and udder health over a whole lactation period.
目的是研究 2 种不同自动脱杯器设置对（1）挤奶特性、（2）奶成分产量、（3）乳头组织状况和（4）乳房健康的影响。在一项随机对照现场试验中，将来自 1 个具有每日 3 次挤奶计划的商业化奶牛场的荷斯坦奶牛（n = 689）分为 2 个处理组。处理包括脱杯器启动奶流阈值为 1.2（ACR1.2）或 0.8 kg/min（ACR0.8）的 57 d。使用电子农场挤奶计获得挤奶特性（奶产量；和挤奶单位开启时间，MUOT）。收集并分析复合奶样以测定脂肪、蛋白质、乳糖和体细胞计数。通过视觉评估机器挤奶引起的乳头组织短期和长期变化。广义线性混合模型显示 MUOT 存在差异，而未检测到奶产量有显著差异。奶产量（最小二乘均值，95%置信区间）分别为 ACR1.2 组和 ACR0.8 组的 11.3（10.9-11.8）和 11.3（10.8-11.8）kg。处理对 MUOT 的影响受胎次修饰。第一、第二和≥第三泌乳期奶牛的 MUOT 分别为 ACR1.2 组的 260.7（252.0-269.4）、257.8（247.4-268.1）和 260.2（252.6-267.9）s；ACR0.8 组的 273.7（264.9-282.5）、279.1（269.4-288.8）和 295.7（287.9-303.6）s。我们未检测到奶成分产量或线性体细胞评分有显著差异。ACR1.2 和 ACR0.8 组的最小二乘均值分别为：乳脂产量，0.42（0.40-0.44）和 0.42（0.40-0.44）kg；乳蛋白产量，0.36（0.35-0.37）和 0.37（0.36-0.37）kg；乳乳糖产量，0.61（0.60-0.63）和 0.63（0.61-0.64）kg，以及线性体细胞评分，1.9（1.8-2.0）和 1.9（1.8-2.0）。广义线性混合模型显示处理对机器挤奶引起的短期变化有影响。ACR1.2 组奶牛发生乳头组织短期变化的可能性较低[优势比（95%置信区间）= 0.78（0.63-0.96）]。处理组之间未检测到机器挤奶引起的乳头组织长期变化有显著差异。将脱杯器启动奶流阈值从 0.8 增加到 1.2 kg/min 可缩短个体挤奶时间并减轻机器挤奶引起的乳头组织短期变化，而不会对挤奶性能或体细胞计数产生不利影响。未来的研究需要调查其对整个泌乳期产奶量和乳房健康的影响。
