Effects of the temperature-humidity index on conception rates in Holstein heifers and cows receiving <i>in vitro</i>-produced Japanese Black cattle embryos

DOI Web Site PubMed 参考文献27件
  • NISHISOZU Takamasa
    Department of Sustainable Agriculture, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan
  • SINGH Jaswant
    Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4, Canada
  • ABE Akinori
    The embryo, Nagamine, Kumamoto 861-8037, Japan
  • OKAMURA Kazuo
    Kumamoto Dairy Cooperative Association, Toshima, Kumamoto 861-8041, Japan
  • DOCHI Osamu
    Department of Sustainable Agriculture, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan

抄録

<p> 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.</p>

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