Short communication: Seasonal effects on development of bovine embryos produced by in vitro fertilization in a hot environment

The objective of this study was to determine if season affected the product ion of in vitro-derived bovine embryos from oocytes of cattle in a subtropi cal environment. Ovaries (similar to 75% beef cattle, including many with B os indicus breeding) were collected from an abattoir. Oocytes were obtained and subjected to in vitro maturation and fertilization. Embryos were then cultured in CR1aa medium. Cleavage rate averaged 72.2 +/- 9.7% and was not different between months of collection. In addition, no differences were ob served in the percent of oocytes or embryos that became blastocysts on d 8 or 9 after insemination. Least-squares means averaged across months for per cent oocytes and cleaved embryos to blastocyst on d 8 were 22.8 +/- 7.5% an d 31.2 +/- 9.4%, respectively. When d 8 blastocysts were classified accordi ng to stage of development (nonexpanded, expanded, and hatched), an effect of month was observed that reflected month-to-month variation and not a con sistent change associated with season. Taken together, results failed to in dicate an effect of season on in vitro production of embryos in a subtropic al environment.