Abstract：
Artificial insemination (AI) and embryo transfer (ET) are important in the reproduction of dairy cows. The conception rate after AI or ET is an essential indicator when selecting appropriate breeding methods. However, information on the environmental factors affecting ET conception rate when compared with AI is limited. We aimed to investigate environmental factors affecting ET conception rate and characterize the differences in environmental factors between AI and ET. Records of the first AI (n = 1,870,143) and ET (n = 29,922) from Holstein nulliparous, primiparous, and multiparous cows in Hokkaido, Japan, were analyzed using separate multivariable logistic regression models. For each breeding method, we grouped primiparous and multiparous cows according to milk yield at peak lactation (PY; < 25, 25-30, 30-35, ≥ 35 kg in primiparous, < 40, 40-45, 45-50, ≥ 50 kg in multiparous) and the interval from calving to first AI or ET (CFI/CFT; < 60, 60-79, 80-99, ≥ 100 d) to evaluate the effects of PY and CFI/CFT on conception rate. AI conception rate decreased with increasing PY in primiparous and multiparous cows, whereas ET conception rate did not decrease significantly. Additionally, the ET conception rate did not decrease even in primiparous and multiparous cows slightly earlier than 60 d in CFI/CFT when compared with those in CFI/CFT after 60 d, which differed from the AI conception rate. Collectively, breeding by ET leads to the avoidance of negative effects of high milk yield and calving on the conception rate, indicating that cows are fertile by ET within 60 d after calving.
摘要：
人工授精（AI）和胚胎移植（ET）在奶牛的繁殖中很重要。选择合适的育种方法时，AI或ET后的受胎率是必不可少的指标。然而,与人工智能相比，影响ET受胎率的环境因素的信息有限。我们旨在研究影响ET受孕率的环境因素，并表征AI和ET之间环境因素的差异。来自Holstein未产的第一个AI（n=1,870,143）和ET（n=29,922）的记录，初产妇,北海道的多胎奶牛，Japan,使用单独的多变量逻辑回归模型进行分析。对于每种育种方法，我们根据泌乳高峰期的产奶量对初产和经产奶牛进行分组（PY；初产<25、25-30、30-35，≥35公斤，<40、40-45、45-50，≥50kg）和从产卵到第一次AI或ET的间隔（CFI/CFT；<60、60-79、80-99，≥100d），以评估PY和CFI/CFT对受孕率的影响。初产和多产奶牛的AI受胎率随PY的增加而降低，而ET受胎率没有明显下降。此外,与CFI/CFT60d后相比，即使初产和多产奶牛的ET受胎率也没有降低，这与人工智能的概念率不同。总的来说，通过ET育种可以避免高产奶量和产卵对受胎率的负面影响，表明奶牛在产卵后60d内可通过ET繁殖。
