Kawashima C, Amaya Montoya C, Masuda Y, Kaneko E, Matsui M, Shimizu T, Matsunaga N, Kida K, Miyake Y-I, Suzuki M, Miyamoto A
Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.
J Dairy Sci. 2007 May;90(5):2279-82. doi: 10.3168/jds.2006-414.
The aim of the present study was to examine the relationship between characteristics of the lactation curve, on the basis of daily milk yield, and ovulation within 3 wk postpartum as an indicator of early return to luteal activity in dairy cows. Lactation records from 46 lactating Holstein cows between calving and 305 d postpartum were studied. Milk samples were collected twice weekly between d 7 and 100 for later determination of progesterone concentrations. Occurrence of an early first ovulation was determined by an increase in milk progesterone by 3 wk after calving. Milk yield was recorded daily until 305 d postpartum, and average yield was calculated weekly. The lactation curve was characterized by 8 indices on the basis of the weekly average of milk yield as follows: a) first-week milk yield; b) peak milk yield; c) actual 305-d milk yield; d) peak week; e) difference in milk yield between the first week and peak week; f) difference in milk yield between the peak week and last week (43rd week postpartum); g) ratio of increase in milk yield between wk 1 and the week of peak yield; and h) ratio of decline in milk yield between the week of peak yield and the last week. Indices g and h were calculated as linear. The number of cows having ovulated by 3 wk postpartum was 22 (47.8%). The resumption of ovarian cycles with normal luteal phases occurred earlier in ovular cows than in anovular cows (32.0 d vs. 57.1 d). Although total milk yield did not differ between ovular and anovular cows, the ratio of increase in milk yield from the first week to the peak week (index g) in ovular cows was smaller compared with that of anovular cows (1.71 vs. 2.54). In addition, the ratio of increase in milk yield from the first week to the third week postpartum was greater in anovular cows by 3 wk postpartum (ovular = 1.43 +/- 0.23 vs. anovular = 2.32 +/- 0.29). In conclusion, the present study demonstrates that a greater increasing ratio of milk yield during early lactation may delay resumption of ovarian cycles after parturition. Therefore, this study is the first to demonstrate statistically that a smaller increasing ratio of milk yield (index g) during early lactation may have a beneficial effect on the first ovulation by 3 wk postpartum.
本研究的目的是基于日产奶量，研究泌乳曲线特征与产后3周内排卵之间的关系，以此作为奶牛黄体活动早期恢复的指标。对46头荷斯坦泌乳奶牛产犊至产后305天的泌乳记录进行了研究。在第7天至第100天期间，每周采集两次牛奶样本，用于后续孕酮浓度的测定。通过产犊后3周牛奶孕酮增加来确定首次早期排卵的发生情况。每天记录产奶量直至产后305天，并计算每周的平均产量。泌乳曲线基于每周平均产奶量由8个指标表征，如下：a）第一周产奶量；b）产奶量峰值；c）实际305天产奶量；d）产奶量峰值周；e）第一周与产奶量峰值周之间的产奶量差异；f）产奶量峰值周与最后一周（产后第43周）之间的产奶量差异；g）第1周与产奶量峰值周之间产奶量增加的比率；h）产奶量峰值周与最后一周之间产奶量下降的比率。指标g和h按线性计算。产后3周内排卵的奶牛数量为22头（47.8%）。有排卵的奶牛比无排卵的奶牛更早恢复具有正常黄体期的卵巢周期（32.0天对57.1天）。尽管有排卵和无排卵奶牛的总产奶量没有差异，但有排卵奶牛从第一周至产奶量峰值周的产奶量增加比率（指标g）低于无排卵奶牛（1.71对2.54）。此外，产后3周时，无排卵奶牛从第一周至产后第三周的产奶量增加比率更高（有排卵奶牛 = 1.43±0.23对无排卵奶牛 = 2.32±0.29）。总之，本研究表明，泌乳早期产奶量增加比率更高可能会延迟产后卵巢周期的恢复。因此，本研究首次从统计学上证明，泌乳早期产奶量增加比率较小（指标g）可能对产后3周的首次排卵具有有益影响。
