Department of Sustainable Agriculture, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4, Canada.
J Reprod Dev. 2023 Apr 3;69(2):72-77. doi: 10.1262/jrd.2022-112. Epub 2023 Jan 31.
We investigated the effect of the temperature-humidity index (THI) on the conception rate (CR) in Holstein heifers and cows receiving in vitro-produced (IVP) Japanese Black cattle fresh embryos. IVP embryos were transferred to Holstein heifers (n = 1,407) and cows (n = 3,189) on 245 commercial farms. The monthly average ambient temperature (AT) and THI ranged from 4.7 to 29°C and 41 to 81, respectively; both were the highest in August. The monthly CR ranged from 16.3% to 46.7% in cows and 23.8% to 74.1% in heifers. The CR of heifers was unaffected by THI, AT, or the month of embryo transfer. However, these parameters affected the CR of cows. The CR at THI values of 61-65 and 71-75 was greater than that at THI > 75, whereas other THI values had no effect. The CR at temperatures > 25°C was lower (P = 0.008) than that at temperatures of 15-20°C and 20-25°C. Moreover, the CR was lowest (P = 0.003) in July. THI and parity (P = 0.057 and P = 0.001, respectively) and AT and parity (P = 0.019 and P = 0.001, respectively) showed significant effects on CR; however, there was no interaction between these two factors. In conclusion, AT > 25°C and THI > 75 adversely affect the CR outcome in cows but not in heifers.
我们研究了温湿度指数（THI）对接受体外受精（IVP）日本黑牛新鲜胚胎的荷斯坦小母牛和奶牛受孕率（CR）的影响。IVP 胚胎被转移到 245 家商业农场的荷斯坦小母牛（n = 1407）和奶牛（n = 3189）身上。每月平均环境温度（AT）和 THI 范围分别为 4.7 至 29°C 和 41 至 81°C，两者均在 8 月达到最高。奶牛的每月 CR 范围为 16.3%至 46.7%，小母牛为 23.8%至 74.1%。小母牛的 CR 不受 THI、AT 或胚胎移植月份的影响。然而，这些参数影响了奶牛的 CR。THI 值为 61-65 和 71-75 的 CR 大于 THI > 75，而其他 THI 值则没有影响。THI 值> 75 的 CR 低于温度> 25°C 的 CR（P = 0.008），而温度为 15-20°C 和 20-25°C 的 CR 则高于温度> 25°C 的 CR。此外，7 月的 CR 最低（P = 0.003）。THI 和胎次（P = 0.057 和 P = 0.001）以及 AT 和胎次（P = 0.019 和 P = 0.001）对 CR 有显著影响；然而，这两个因素之间没有相互作用。总之，AT > 25°C 和 THI > 75 会对奶牛的 CR 结果产生不利影响，但对小母牛没有影响。
