Journal
JOURNAL OF REPRODUCTION AND DEVELOPMENT
Volume 69, Issue 2, Pages 72-77Publisher
SOCIETY REPRODUCTION & DEVELOPMENT-SRD
Keywords
Ambient temperature; Conception rate; Embryo transfer; Holstein cattle; Temperature-humidity index (THI)
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This study investigated the effect of temperature-humidity index (THI) on the conception rate (CR) in Holstein heifers and cows receiving in vitro-produced (IVP) Japanese Black cattle embryos. The results showed that THI and ambient temperature had a significant impact on the CR of cows, but not heifers. Temperature above 25 degrees Celsius and THI above 75 adversely affected the CR outcome in cows.
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? 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 degrees C was lower (P = 0.008) than that at temperatures of 15-20? and 20-25?. 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? and THI > 75 adversely affect the CR outcome in cows but not in heifers.
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