Department of Animal Nutrition, Autonomous Agrarian University Antonio Narro, Saltillo, Mexico.
J Dairy Sci. 2011 Sep;94(9):4524-30. doi: 10.3168/jds.2011-4152.
Records representing data from 1,500 barren Holstein cows over an 8-yr period from a large commercial dairy farm in northern Mexico were analyzed to determine the effects of lactation number and season and year of initiation of lactation on milk production of cows induced hormonally into lactation and treated with recombinant bovine somatotropin (rbST) throughout lactation. Peak and 305-d milk yields were also assessed as predictors of total milk yield in cows induced into lactation. A significant quadratic relationship was found between 305-d milk yield and number of lactation [7,607±145 and 9,548±181 kg for first- and ≥6-lactation cows, respectively; mean ± standard error of the mean (SEM)] with the highest production occurring in the fifth lactation. Total milk yields of cows with ≤2 lactations were approximately 4,500 kg less than milk yields of adult cows (the overall average ± standard milk yield was 13,544±5,491 kg per lactation and the average lactation length was 454±154 d). Moreover, 305-d milk production was depressed in cows induced into lactation in spring (8,804±153 kg; mean ± SEM) and summer (8,724±163 kg) than in fall (9,079±151 kg) and winter (9,085±143 kg). Partial regression coefficients for 305-d milk yield and peak milk yield indicated an increment of 157 kg of milk per lactation per 1-kg increase in peak milk yield (r(2)=0.69). Neither peak milk yield (r(2)=0.18) nor 305-d milk yield (r(2)=0.29) was accurate for predicting total milk yield per lactation. Year, parity, and season effects had significant influence on milk yield of cows induced into lactation and treated with rbST throughout lactation, and peak milk yield can assist in the prediction of 305-d milk yield but not total milk yield. This study also showed that hormonal induction of lactation in barren high-yielding cows is a reliable, practical, and affordable technique in countries where rbST treatment and prolonged steroid administration of dairy cows are legally permitted.
对来自墨西哥北部一个大型商业奶牛场的 1500 头空怀荷斯坦奶牛在 8 年期间的数据记录进行了分析，以确定泌乳次数、季节和泌乳起始年份对接受激素诱导泌乳并在整个泌乳期使用重组牛生长激素（rbST）治疗的奶牛的产奶量的影响。还评估了高峰奶产量和 305 天奶产量作为诱导泌乳奶牛总产奶量的预测指标。发现 305 天奶产量与泌乳次数之间存在显著的二次关系[第一泌乳次数和≥6 次泌乳次数的奶牛分别为 7、607±145 和 9、548±181kg；均值±均值的标准误差（SEM）]，第五次泌乳的产奶量最高。泌乳次数≤2 的奶牛的总产奶量比成年奶牛的产奶量低约 4500kg（总体平均±标准产奶量为每泌乳期 13544±5491kg，平均泌乳期长度为 454±154d）。此外，在春季（8、804±153kg；均值±SEM）和夏季（8、724±163kg）诱导泌乳的奶牛的 305 天产奶量低于秋季（9、079±151kg）和冬季（9、085±143kg）。305 天奶产量和高峰奶产量的偏回归系数表明，每增加 1kg 高峰奶产量，每泌乳期的奶产量就会增加 157kg（r(2)=0.69）。高峰奶产量（r(2)=0.18）和 305 天奶产量（r(2)=0.29）均不能准确预测每泌乳期的总产奶量。年份、胎次和季节对接受 rbST 治疗并在整个泌乳期接受激素诱导泌乳的奶牛的产奶量有显著影响，高峰奶产量有助于预测 305 天奶产量，但不能预测总产奶量。这项研究还表明，在允许使用 rbST 处理和延长奶牛类固醇给药的国家，激素诱导空怀高产奶牛泌乳是一种可靠、实用且负担得起的技术。
