Burke C R, Roche J R
Dexcel Limited, Private Bag 3221, Hamilton, New Zealand.
J Dairy Sci. 2007 Sep;90(9):4304-12. doi: 10.3168/jds.2006-788.
Extended postpartum anovulatory intervals (PPAI) are a major contributor to infertility in seasonal dairy systems constrained to 365-d calving intervals. This study was conducted to evaluate the effects of pasture-based dietary energy intakes during the transitional calving period on PPAI. Sixty-eight multiparous Holstein-Friesian cows were assigned to high [11.9 kg of dry matter (DM)/d] or low (4.8 kg of DM/d) pasture intakes for 29 +/- 7.7 d prepartum. After calving, cows within each prepartum diet were assigned to either a high (13.5 kg of DM/d) or low (8.6 kg of DM/d) pasture intake for 35 d in a 2 x 2 factorial arrangement. Progesterone concentrations were measured in milk samples collected twice weekly to determine PPAI, which was defined as the day on which progesterone level was elevated to > or = 3 ng/mL with subsequent concentrations being consistent with an ovulatory cycle. Blood samples were collected before initiation of treatments, and at d -21, -14, -7, 0 (day of calving), 1, 2, 3, 4, 7, 14, 21, 28, and 35 in all cows. The PPAI was associated with body condition score, concentrations of plasma insulin and insulin-like growth factor-I, and growth hormone. Postpartum intake did not affect these metabolic hormones or PPAI, but yield of FCM during the first 35 d was reduced by 23% among cows on a restricted intake. No relationships were found between PPAI and milk production characteristics. These data demonstrate that when pasture is the sole dietary source during the calving transition period, PPAI may be influenced by prepartum intake levels, whereas postpartum intake influences milk yield, but not PPAI. The underlying mechanism(s) that associates the prepartum period to PPAI may involve the sensitivity of the growth hormone-insulin-like growth factor axis to dietary intake levels. Nonetheless, PPAI in grazing multiparous dairy cows appears largely unresponsive to intake levels during the calving transition period.
在受365天产犊间隔限制的季节性奶牛养殖系统中，延长的产后无排卵间隔（PPAI）是导致不孕的主要因素。本研究旨在评估产犊过渡期基于牧场的日粮能量摄入量对PPAI的影响。68头经产荷斯坦-弗里生奶牛在产前29±7.7天被分配到高（11.9千克干物质（DM）/天）或低（4.8千克DM/天）的牧场采食量组。产犊后，将每组产前日粮的奶牛以2×2析因设计分配到高（13.5千克DM/天）或低（8.6千克DM/天）的牧场采食量组，为期35天。每周采集两次牛奶样本测量孕酮浓度以确定PPAI，PPAI定义为孕酮水平升高至≥3纳克/毫升且随后浓度与排卵周期一致的那天。在所有奶牛开始处理前以及第-21、-14、-7、0（产犊日）、1、2、3、4、7、14、21、28和35天采集血样。PPAI与体况评分、血浆胰岛素和胰岛素样生长因子-I浓度以及生长激素有关。产后采食量不影响这些代谢激素或PPAI，但采食量受限的奶牛在前35天的乳脂校正乳产量降低了23%。未发现PPAI与产奶特性之间的关系。这些数据表明，当牧场是产犊过渡期唯一的日粮来源时，PPAI可能受产前采食量水平的影响，而产后采食量影响产奶量，但不影响PPAI。将产前时期与PPAI联系起来的潜在机制可能涉及生长激素-胰岛素样生长因子轴对日粮采食量水平的敏感性。尽管如此，放牧经产奶牛的PPAI在产犊过渡期似乎对采食量水平基本无反应。
