VIABILITY OF VITRIFIED EMBRYOS FROM ROMOSINUANO AND TROPICAL MILKING CATTLE OVER TWO SEASONS OF THE YEAR IN VERACRUZ, MEXICO

The seasons of the year in tropical climates affect the behavior of female cattle of different breeds. The aim of this study was to determine the effect of the weather season on the viability of vitrified embryos on the Tropical Milking (TM) and Romosinuano (RM) breeds. Ultrasound-guided follicular aspiration sessions, in vitro fertilization, and embryo vitrification were carried out during two seasons: hot-dry (HD) and hot-humid (HH). A total of 31 RM and 27 TM donors were used, and data were collected on the viability of oocytes and embryos. The response variables observed in the devitrified embryos were the capacity of eclosion (CE), blastocele reconstitution (BL), trophoblast (TR), zona pellucida (ZP), and cell mass (CM). For cell viability, the number of live cells (LIV) and dead cells (DEC) were considered. The data were analyzed using a generalized linear model with the GENMOD procedure of SAS®. Multiple comparison tests and adjusted mean differences were performed with the Tukey test. An effect on the season × breed interaction (p ≤ 0.0001) was observed in the characteristics studied. The TM breed displayed higher values in five characteristics (p ≤ 0.0001), and the HH season (p ≤ 0.001) in four characteristics. No breed effect was found on cell viability. However, in the HH season, the number of dead cells was lower (p ≤ 0.04). Seasonal climatic variation in Southeastern Mexico had effects on the vitrified embryos.