Nabenishi H, Yamazaki A
Laboratory of Animal Feeding and Management, Department of Animal Science, School of Veterinary Medicine, Kitasato University, Towada, Aomori, Japan.
Reprod Domest Anim. 2017 Jun;52(3):371-375. doi: 10.1111/rda.12917. Epub 2017 Feb 19.
Environmental factors such as the temperature-humidity index (THI) are known to affect reproductive parameters in cattle. Therefore, here, we examined whether there was any correlation between the THI and the reproductive performance of Japanese Black cattle by analysing the first-service conception rates of 178,492 artificially inseminated cows across 9,833 herds in south-western Japan over a 3-year period. The daily mean (±SD) THI over the study period was 63.6 ± 11.3 (range: 41.4-81.5). The calving to first artificial insemination (AI) interval was significantly negatively correlated with THI in the month of AI (r = -.75, p < .001), whereas conception rate to first AI (CRFA) showed a cyclical change that did not correspond with that of THI, resulting in a time lag between CRFA and THI in the month of AI. Furthermore, there was a stronger correlation between CRFA and THI between 3 and 2 months before AI (r = .76 vs. .83, p < .001) than in the month of AI (r = .34, p = .04). Therefore, this extensive field study showed that a decrease in THI was associated with declined reproductive performance in Japanese Black cattle and that the impact of the cold environment on the conception rate is attributable to a carryover effect from the cold season before AI rather than conditions at the time of AI.
众所周知，诸如温度湿度指数（THI）等环境因素会影响牛的繁殖参数。因此，在此我们通过分析日本西南部9833个牛群中178492头人工授精母牛在3年期间的首次输精受胎率，研究了THI与日本黑牛繁殖性能之间是否存在相关性。研究期间的每日平均（±标准差）THI为63.6±11.3（范围：41.4 - 81.5）。产犊至首次人工授精（AI）的间隔与AI当月的THI呈显著负相关（r = -0.75，p < 0.001），而首次AI的受胎率（CRFA）呈现出与THI不对应的周期性变化，导致AI当月CRFA与THI之间存在时间滞后。此外，AI前3至2个月时CRFA与THI之间的相关性（r = 0.76对0.83，p < 0.001）比AI当月（r = 0.34，p = 0.04）更强。因此，这项广泛的田间研究表明，THI降低与日本黑牛繁殖性能下降有关，寒冷环境对受胎率的影响归因于AI前寒冷季节的残留效应，而非AI时的环境条件。
