Department of Animal Science, Shiraz University, Shiraz, Iran.
J Dairy Sci. 2012 May;95(5):2718-22. doi: 10.3168/jds.2011-4954.
The aim of the present study was to estimate the effect of dystocia on lactation performance, using an incomplete gamma function. Data from March 2000 to April 2009 comprising 100,628 lactations of 65,421 cows in 204 dairy herds collected by the Animal Breeding Center of Iran were used. Of 100,628 births, 91.8% required no assistance, whereas 8.2% required assistance of some sort. Factors associated with the presence of dystocia were calving season, calving year, herd, calf sex, parity, and age of dam. Peak yield for primiparous cows with dystocia at calving occurred on d 87.2 [standard error (SE) 0.47], and for primiparous cows with easy calving, the peak of lactation was on d 83.3 (0.25). Peak yield was lowered by 0.39 (SE 0.07), 2.20 (SE 0.15), 2.22 (SE 0.21), and 2.54 (SE 0.32) kg for cows with incidence of dystocia compared with normal cows in parity 1 to 4, respectively. Dystocia was associated with decreased 305-d lactation performance in all parities, mostly in early lactation. Although more difficult births occurred in heifer calvings, loss in lactation performance was greater in second or later lactations following a difficult birth.
本研究旨在使用不完全伽马函数估计难产对泌乳性能的影响。使用伊朗动物繁殖中心于 2000 年 3 月至 2009 年 4 月期间收集的 204 个奶牛场的 65421 头奶牛的 100628 次泌乳数据。在 100628 次分娩中，91.8%无需任何帮助，而 8.2%需要某种帮助。与难产有关的因素包括产犊季节、产犊年份、牛群、犊牛性别、胎次和母牛头胎年龄。难产初产奶牛的产奶高峰期出现在第 87.2 天（标准误 0.47），而顺产初产奶牛的泌乳高峰期出现在第 83.3 天（0.25）。与正常分娩的 1 至 4 胎奶牛相比，难产奶牛的产奶高峰分别降低了 0.39（SE 0.07）、2.20（SE 0.15）、2.22（SE 0.21）和 2.54（SE 0.32）kg。难产与所有胎次的泌乳性能下降有关，主要发生在泌乳早期。尽管在小母牛产犊中发生了更困难的分娩，但在经历了困难分娩后的第二次或以后的泌乳期中，泌乳性能的损失更大。
