Cordoba M C, Fricke P M
Department of Dairy Science, University of Wisconsin, Madison 53706-1284, USA.
J Dairy Sci. 2002 Jul;85(7):1752-63. doi: 10.3168/jds.S0022-0302(02)74249-5.
Lactating dairy cows (n = 228) in a semiseasonal, grazing-based dairy were subjected to artificial insemination (AI) to start the 23-d breeding season (d 0 to 22) followed by natural service (d 23 to 120). Cows were randomly assigned to: 1) Ovsynch (GnRH, d -10; PGF2,, d -3; GnRH, d -1; timed AI, d 0) followed by AI at estrus (tail paint removal) on d 1 to 22 (Ovsynch; n = 114); or 2) AI at estrus (tail paint removal) throughout 23 d of AI breeding (tail paint; n = 114). Days to first AI service were greater and the 23-d AI service rate was less for tail paint vs. Ovsynch cows (12.0 +/- 0.6 d vs. 0 d; and 84.2 vs. 100%, respectively). However, conception to first AI was greater for tail paint vs. Ovsynch cows (47.3 vs. 27.3%, respectively). Cows in the tail paint group received only one AI, during 23 d of AI, but 46.4% of Ovsynch cows received a second AI, with similar conception (43.1%) to that of tail paint cows at first AI (47.3%). Based on serum progesterone, incomplete luteal regression after PGF2alpha, and poor ovulatory responses to GnRH contributed to lower conception to timed AI in the Ovsynch group. Cumulative pregnancy rates for tail paint and Ovsynch cows did not differ after 23 d of AI breeding (47.3 vs. 46.3%, respectively) nor after 120 d of AI/ natural service breeding (80.5 vs. 83.3%, respectively). Lactating cows in this grazing-based dairy synchronized poorly to Ovsynch resulting in reduced conception to timed AI compared with AI after tail paint removal.
在一个半季节性、以放牧为主的奶牛场中，228头泌乳奶牛接受了人工授精（AI），开启了为期23天的繁殖季节（第0天至22天），随后是自然交配（第23天至120天）。奶牛被随机分为两组：1）Ovsynch方案（促性腺激素释放激素[GnRH]，第-10天；前列腺素F2α[PGF2α]，第-3天；GnRH，第-1天；定时人工授精，第0天），然后在第1天至22天发情期（去除尾漆）时进行人工授精（Ovsynch组；n =
114头）；或2）在整个23天的人工授精繁殖期内，在发情期（去除尾漆）时进行人工授精（尾漆组；n = 114头）。与Ovsynch组奶牛相比，尾漆组奶牛首次人工授精的天数更多，23天人工授精成功率更低（分别为12.0±0.6天对0天；84.2%对100%）。然而，尾漆组奶牛首次人工授精的受孕率高于Ovsynch组奶牛（分别为47.3%对27.3%）。尾漆组奶牛在23天的人工授精期间只接受了一次人工授精，但46.4%的Ovsynch组奶牛接受了第二次人工授精，其受孕率（43.1%）与尾漆组奶牛首次人工授精时的受孕率（47.3%）相似。基于血清孕酮水平，PGF2α处理后黄体退化不完全以及对GnRH的排卵反应不佳，导致Ovsynch组定时人工授精的受孕率较低。在23天的人工授精繁殖后，尾漆组和Ovsynch组奶牛的累积妊娠率没有差异（分别为47.3%对46.3%），在120天的人工授精/自然交配繁殖后也没有差异（分别为80.5%对83.3%）。在这个以放牧为主的奶牛场中，泌乳奶牛对Ovsynch方案的同步性较差，与去除尾漆后进行人工授精相比，定时人工授精的受孕率降低。
