Impact of summer heat stress on the thermal environment of bovine female genital tract
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Impact of summer heat stress on the thermal environment of bovine female genital tract Hossam El-Sheikh Ali 1,2,3
&
Youji Tamura 1 & Hiroshi Sameshima 4 & Go Kitahara 1
Received: 8 April 2020 / Accepted: 7 September 2020 # Springer Nature B.V. 2020
Abstract 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 < 0.05) in comparison to winter and spring. THI was positively correlated (P < 0.01) with RT, VT, CT, UBT, and UHT. Linear regression revealed that VT, CT, UBT, and UHT increased by 0.05 °C per unit of THI. VT was more highly correlated than RT with THI and with the temperature of other regions of genital tract. HS induced increases in the temperatures of different regions of the female genital tract. The relationship between THI and VT could be incorporated into a mathematical model to predict the thermal load of HS on different regions of the female genital tract. Keywords Digital thermometer . Estradiol-17β (E2) . Estrous cycle . Female genital tract . Progesterone (P4) . Temperature gradient
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11250-020-02378-4) contains supplementary material, which is available to authorized users. * Go Kitahara [email protected] 1
Laboratory of Theriogenology, Faculty of Agriculture, University of Miyazaki, Nishi 1-1, Gakuen-Kibanadai, Miyazaki 889-2192, Japan
2
Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
3
Department of Theriogenology, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt
4
Department of Obstetrics and Gynecology, Faculty of Medicine, University of Miyazaki, Miyazaki 889-1692, Japan
Summer heat stress (HS) negatively affects the reproductive performance and income of dairy and beef farms, because it is associated with a reduction in conception rate, increase in services per conception, and early embryonic death (Drost and Thatcher 1987; De
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