Effects of Maternal Thermal Stress on the Number of Retrieved Oocytes by Ovum Pick Up and Subsequent Embryo Development in Dairy Cattle

다국어 초록 (Multilingual Abstract)

High environmental temperatures observed during the summer month reduce bovine reproduction and fertility. In this study, we examined the effect of maternal thermal stress on the number of immature oocytes retrieved by OPU procedure from Jersey heifers and their subsequent embryo developmental competence. Total 57, 69, 81 immature oocytes were retrieved from same donors (n = 3) in May (spring), June (early summer) and July (summer), respectively. Blastocyst rates were 33.3, 34.8 and 24.8% in spring, early summer and summer, respectively. Interestingly, we observed that the number of retrieved oocytes from donors were higher under extreme hot temperature (summer) than moderated temperature (spring). In contrast, blastocyst rates were lower under the hot weather. It is presumed that the reason for the increased number of retrieved oocytes in summer is associated with increased FSH levels by reduced progesterone levels due to impaired corpus luteum. And reduced embryo developmental competence in hot weather is thought to be associated with disruption of nuclear and cytoplasmic maturation. Taken together, our result suggest that maternal thermal stress affects the number of retrieved oocytes from dairy heifers and embryo developmental competence.