Effect of acute and chronic caloric heat stress on oocyte quality of adapted breeds cattle

ABSTRACT In tropical regions, the use of adapted breeds has been a strategy to minimize the effect of heat stress (HS) in cattle. However, information quantifying stress and its effect on reproduction of these breeds is lacking. The aim of this study was to evaluate the quality of the recovered oocyte and some physiological parameters that indicate HS in adapted breed. Bos taurus x Bos indicus (n=6) and Pantaneira (n=12) cows, located in the transition region between Cerrado and Brazilian Pantanal, underwent follicular aspiration guided by ultrasound (OPU) in different weather conditions. Eight sessions of OPU were carried out, with a minimum interval of 7 days and maximum 54 days between sessions. For weather characterization, the temperature and humidity index (THI) was calculated. THI of the day of OPU, 7 days before and 60 days before each session were calculated. The physiological parameters and oocyte viability of Girolando and Pantaneira cows were not negatively influenced under ITU between 72 and 78. The chronic HS (60 days)may affect the oocyte viability of Pantaneira donors when ITU is over 75.

摘要：在热带地区，采用适应性品种牛是缓解热应激（heat stress, HS）对牛只负面影响的常用策略。然而，目前尚缺乏量化此类品种应激反应及其对繁殖性能影响的相关研究数据。本研究旨在评估适应性品种牛回收卵母细胞的质量，以及部分可表征热应激的生理参数。本试验选取饲养于塞拉多（Cerrado）与巴西潘塔纳尔（Brazilian Pantanal）过渡地带的普通牛×瘤牛杂交牛（Bos taurus x Bos indicus，n=6）及潘塔纳尔牛（Pantaneira，n=12）共18头，在不同气象条件下开展超声引导下卵泡抽吸术（ovum pick-up, OPU）。共完成8次OPU操作，各次操作间隔最短为7天，最长为54天。气象特征表征采用温湿度指数（temperature and humidity index, THI），分别计算每次OPU当日、OPU前7天及OPU前60天的THI值。结果显示，当THI处于72~78区间时，Girolando牛（即上述普通牛×瘤牛杂交牛）与潘塔纳尔牛的生理参数及卵母细胞活力未受到显著负面影响；当60天周期的慢性热应激下THI超过75时，潘塔纳尔牛供体的卵母细胞活力可能会受到不利影响。