Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
National Livestock Breeding Center, Nishigo, Fukushima, Japan.
Anim Sci J. 2022 Jan-Dec;93(1):e13688. doi: 10.1111/asj.13688.
Only a few, principal, weather stations in Japanese prefectures have the daily humidity records required to calculate the temperature-humidity index (THI) as a dairy cow heat-stress indicator. We compared three heat-stress indices: (1) THI calculated from daily average temperature and daily relative humidity at a principal weather station (PTHI); (2) daily average temperature at each herd's closest local weather station (TEMP); and (3) THI calculated from daily average temperature at each herd's closest local weather station and daily relative humidity at the principal weather station (HTHI). We used daily records from 532 provincial weather stations and test-day records of milk production from Days 6 to 305 post-first-calving in Holsteins to compare the indices as indicators of heat-stress effects on milk yield and somatic cell score (SCS). The models used the BLUPF90 package to analyze the effects of herd-year, calving age, days in milk, and PTHI, TEMP, or HTHI. We estimated each model's mean square error (MSE) and compared suitabilities among indices for each trait. TEMP heat-stress thresholds were ~18°C (milk yield) and 15-20°C (SCS). The MSE of the HTHI model was the smallest, but no significant differences were found among the indices for milk yield.
仅有少数几个日本都道府县的主要气象站拥有计算温度-湿度指数（THI）所需的每日湿度记录，THI 是一种奶牛热应激指标。我们比较了三种热应激指数：（1）由主要气象站的每日平均温度和每日相对湿度计算得出的 THI（PTHI）；（2）每个牛群最近的当地气象站的每日平均温度（TEMP）；以及（3）由每个牛群最近的当地气象站的每日平均温度和主要气象站的每日相对湿度计算得出的 THI（HTHI）。我们使用了 532 个省级气象站的日记录和荷斯坦牛产后第 6 天至第 305 天的产奶测试日记录，比较了这些指数作为产奶量和体细胞评分（SCS）受热应激影响的指标。所使用的模型采用了 BLUPF90 包来分析牛群-年份、产犊年龄、泌乳天数以及 PTHI、TEMP 或 HTHI 的影响。我们估计了每个模型的均方误差（MSE），并比较了各指数对各性状的适宜性。TEMP 热应激阈值约为 18°C（产奶量）和 15-20°C（SCS）。HTHI 模型的 MSE 最小，但产奶量各指数之间没有显著差异。
