Impact of summer heat stress on the thermal environment of bovine female genital tract

Summer heat stress (HS) is associated with a reduction in conception rate, increase in services per conception, and early embryonic death. However, the impact of summer HS on the thermal environment of different regions of the bovine female genital tract remains unknown. This study aimed to elucidate the effect of summer HS on the thermal environment of different regions of the genital tract in the cow. Three non-pregnant Japanese Black cows were investigated using a specially designed digital thermometer to record the temperatures of the rectum (RT), vagina (VT), cervix (CT), uterine body (UBT), and uterine horns (UHT) on days 0, 1, 2, 3, and 8 of the estrous cycle (day 0 = heat) in February (winter), May (spring), and August (summer). During the experiment, the temperature humidity index (THI) was recorded. THI during summer was higher (P ˂ 0.001) than in winter and spring (78.45 ± 0.32 vs. 60.26 ± 1.20 and 68.51 ± 0.80, respectively) and was higher than the alert THI indicating HS (i.e., THI > 73). Consequently, the VT, CT, UBT, and UHT were elevated during summer HS (P