Pennington J A, Malven P V
J Dairy Sci. 1985 May;68(5):1116-22. doi: 10.3168/jds.S0022-0302(85)80937-1.
Twenty-three primiparous heifers and pluriparous cows were milked once daily beginning 3 to 10 days before parturition. Retrospectively, they were divided into groups representing either successful or unsuccessful premature induction of lactogenesis, depending on milk production prior to calving. Successfully induced animals had prepartum milk yields greater than 4 kg/milking and unsuccessful animals yielded less. Ten of 23 animals satisfied the criterion for successful premature induction at 2.6 +/- .4 days before calving and 3.6 +/- .8 days after first milking and had peak prepartum yields of 7.9 +/- .7 kg/milking. Total number of prepartum days milked did not differ between successful and unsuccessful groups. Greater milk yield prepartum was significantly associated with higher milk prolactin concentration on days -6 to -4. Heifers had less milk yield than cows but did not differ in milk prolactin concentration or in total prolactin per milking. Premature induction of lactogenesis did not confer significant lactational benefits for more than 1 day postpartum or over the first 35 days postpartum. Premature induction of lactogenesis as a result of prepartum milking did not, as hypothesized, decrease the ability of mammary secretions to accumulate prolactin in large amounts. All groups rapidly lost this ability after parturition, suggesting that the hormonal environment of late pregnancy may promote the transfer of prolactin from blood into milk when there is regular removal of prepartum milk.
23头初产小母牛和经产母牛在分娩前3至10天开始每天挤奶一次。回顾性地，根据产犊前的产奶量，将它们分为代表早产奶成功或失败的组。成功诱导的动物产前产奶量大于4千克/次挤奶，而失败的动物产奶量较少。23头动物中有10头在产犊前2.6±0.4天和首次挤奶后3.6±0.8天达到早产奶成功的标准，产前产奶量峰值为7.9±0.7千克/次挤奶。成功组和失败组产前挤奶的总天数没有差异。产前产奶量较高与-6至-4天的催乳素浓度较高显著相关。小母牛的产奶量低于母牛，但催乳素浓度或每次挤奶的总催乳素量没有差异。早产奶对产后超过1天或产后前35天没有显著的泌乳益处。如假设的那样，产前挤奶导致的早产奶并没有降低乳腺分泌物大量积累催乳素的能力。所有组在分娩后都迅速丧失了这种能力，这表明当定期去除产前奶时，妊娠后期的激素环境可能促进催乳素从血液向乳汁的转移。
