Department of Animal Science, University of Vermont, Burlington, VT 05405, USA.
J Anim Sci. 2013 Jan;91(1):195-202. doi: 10.2527/jas.2012-5692. Epub 2012 Oct 16.
In dairy cows, increased milking frequency (IMF) during early lactation stimulates an increase in milk yield that partially persists through the remainder of lactation. However, the effects of IMF on lactation performance and udder health of primiparous heifers have not been clearly established. The objective of this study was to determine the effects of IMF during early lactation on milk yield and composition, udder edema, and teat-end condition of primiparous Holstein heifers. Thirteen heifers were assigned at parturition to unilateral frequent milking (twice-daily milking of the left udder half (2X), and 4-times-daily milking of the right udder half (4X)) from d 1 to 21 of lactation. Heifers were milked twice daily at 0130 and 1330 h, with additional milking of the right udder half at 0430 and 1630 h. Half-udder milk yield and composition were recorded on d 1 and 4, weekly through 35 d in milk (DIM), monthly through 210 DIM, and on d 270±1 of lactation. Udder edema and teat-end scores were evaluated on d 1 and 4, weekly through d 35, and on d 60±1 of lactation. A 1-sided paired t test was used to compare milk yield of 4X- to 2X-udder halves. A 2-sided paired t test was used to test for differences in milk composition, udder edema, and teat-end scores. Overall, 4X stimulated an immediate increase in milk yield. Differential milk yield peaked on d 21 of lactation, with 4X udder halves producing 2.8 kg/d more milk than 2X udder halves (P<0.001). After cessation of 4X, the milk yield differential decreased, but 4X udder halves continued to produce 0.8 kg/d more milk than 2X udder halves through d 270 of lactation (P<0.05). Over the entire lactation, milk component yields and 3.5% fat-corrected milk or energy-corrected milk were greater (P<0.05), whereas somatic cell counts in milk were lower, in 4X udder halves (P<0.05). Udder edema and teat-end condition did not differ between 4X and 2X (P>0.19). In conclusion, IMF during early lactation stimulated a persistent increase in milk yield without negatively affecting several indicators of udder health of primiparous dairy heifers.
在奶牛中，早期泌乳时增加挤奶频率（IMF）会刺激产奶量增加，这种增加在泌乳期的剩余时间内部分持续。然而，IMF 对初产荷斯坦奶牛泌乳性能和乳房健康的影响尚未明确。本研究的目的是确定早期泌乳期 IMF 对初产荷斯坦奶牛产奶量和组成、乳房水肿和乳头部状况的影响。在分娩时，13 头奶牛被分配到单侧频繁挤奶（从泌乳第 1 天到第 21 天，每天两次挤左侧乳房的一半（2X），每天 4 次挤右侧乳房的一半（4X））。奶牛在 0130 和 1330 小时进行两次挤奶，在 0430 和 1630 小时额外挤右侧乳房的一半。在第 1 天和第 4 天记录半乳产量和组成，在第 35 天、第 7 天至第 210 天和第 270±1 天泌乳期间每周记录一次。在第 1 天和第 4 天评估乳房水肿和乳头部评分，在第 35 天和第 60±1 天每周评估一次。使用单侧配对 t 检验比较 4X-和 2X-侧乳房的产奶量。使用双侧配对 t 检验检验乳成分、乳房水肿和乳头部评分的差异。总体而言，4X 刺激产奶量立即增加。差异产奶量在泌乳第 21 天达到峰值，4X 侧乳房比 2X 侧乳房多产奶 2.8 公斤/天（P<0.001）。停止 4X 后，产奶量差异减少，但 4X 侧乳房在整个泌乳期仍比 2X 侧乳房多产奶 0.8 公斤/天（P<0.05）。整个泌乳期，牛奶成分产量和 3.5%乳脂校正奶或能量校正奶较高（P<0.05），而牛奶中的体细胞计数较低（P<0.05）。4X 和 2X 之间的乳房水肿和乳头部状况没有差异（P>0.19）。总之，早期泌乳期的 IMF 刺激了产奶量的持续增加，而不会对初产奶牛的几个乳房健康指标产生负面影响。
