Cuttance E L, Mason W A
a VetEnt , Te Awamutu , New Zealand.
N Z Vet J. 2015 Sep;63(5):276-83. doi: 10.1080/00480169.2015.1031292. Epub 2015 Jun 18.
To determine some of the risk factors for cows not observed in oestrus within 35-42 days of an unsuccessful artificial insemination (AI; phantom cows), and the reproductive outcomes and effect of treatment of phantom cows.
Over 2 years, in dairy herds from the Waikato (n=10) and Canterbury (n=4) regions of New Zealand, pregnancy diagnosis was carried out 35-42 days after AI on cows that had been inseminated in the first 3 weeks after the start of mating (PSM) but had not been seen returning to oestrus. Risk factors for phantom cows were analysed using a generalised linear mixed effect model. In Year 1, all phantom cows were left untreated. In Year 2, phantom cows were categorised as having a corpus luteum (CL) (CL+ n=120), or having ovarian follicles≥10 (n=101) or <10 (n=40) mm in diameter. Cows with a CL were treated with cloprostenol or untreated and placed with bulls. Cows with no CL received intravaginal progesterone (P4) for 7 days, with injection of gonadotrophin-releasing hormone (GnRH) on Days 0 and 9, and cloprostenol on Day 7 followed by AI. Pregnancy diagnosis of all cows took place 100-120 days after PSM and interval to conception and final pregnancy rate determined.
Overall, of cows inseminated in the first 3 weeks after PSM that did not return to oestrus, 610/6,734 (9.1%) were phantom cows. From the final multivariable analysis, treatment for anoestrus, BCS≤4.0 at mating, being 2 or >6 years of age, and pure-bred, and decreasing interval between calving and mating, until 98 days post calving, were associated with increased odds of being a phantom cow. Compared to all other groups of cows, phantom cows had a longer interval to conception (p<0.001) and a lower final pregnancy rate (p<0.001). Treatment of CL+ cows or cows with follicles≥10 mm did not affect reproductive outcomes (p>0.3). For cows with follicles<10 mm treatment decreased the final percentage not pregnant (3/27; 11%; p=0.01) and interval to conception (21 days; p=0.02) compared with controls (7/13; 54% and 37 days, respectively).
Risk factors for phantom cows were identified that could be manipulated to reduce the number of phantom cows in a herd, in particular increasing BCS. Treatment of the majority of phantom cows did not improve reproductive performance.
确定在人工授精（AI；模拟母牛）失败后35 - 42天内未观察到发情的母牛的一些风险因素，以及模拟母牛的繁殖结果和治疗效果。
在两年多的时间里，对新西兰怀卡托地区（n = 10）和坎特伯雷地区（n = 4）的奶牛群进行研究。在配种开始后的前三周（PSM）内进行人工授精但未观察到发情的母牛，在人工授精后35 - 42天进行妊娠诊断。使用广义线性混合效应模型分析模拟母牛的风险因素。在第一年，所有模拟母牛均未接受治疗。在第二年，模拟母牛被分类为有黄体（CL）（CL + n = 120），或卵巢卵泡直径≥10（n = 101）或<10（n = 40）mm。有黄体的母牛用氯前列醇治疗或不治疗并与公牛配种。无黄体的母牛接受7天的阴道内孕酮（P4）治疗，在第0天和第9天注射促性腺激素释放激素（GnRH），在第7天注射氯前列醇，随后进行人工授精。所有母牛在PSM后100 - 120天进行妊娠诊断，并确定受孕间隔和最终妊娠率。
总体而言，在PSM后前三周内人工授精且未发情的母牛中，610/6734（9.1%）为模拟母牛。从最终的多变量分析来看，发情期治疗、配种时体况评分（BCS）≤4.0、年龄为2岁或>6岁、纯种，以及产犊与配种之间的间隔缩短直至产犊后98天，均与成为模拟母牛的几率增加有关。与所有其他母牛组相比，模拟母牛的受孕间隔更长（p<0.001），最终妊娠率更低（p<0.001）。对有黄体的母牛或卵泡≥10 mm的母牛进行治疗，对繁殖结果没有影响（p>0.3）。对于卵泡<10 mm的母牛，与对照组（分别为7/13；54%和37天）相比，治疗降低了最终未怀孕的百分比（3/27；11%；p = 0.01）和受孕间隔（21天；p = 0.02）。
确定了模拟母牛的风险因素，可通过控制这些因素来减少牛群中模拟母牛的数量；尤其是增加体况评分。对大多数模拟母牛进行治疗并不能改善繁殖性能。
