VIABILITY OF IN VITRO PRODUCED EMBRYOS OF GYR CATTLE (Bos indicus) AFTER CRYOPRESERVATION BY VITRIFICATION UNDER FIELD CONDITIONS

The aim of this study was to evaluate the pregnancy rate of in vitro produced embryos of Gyr cattle (Bos indicus) after cryopreservation by the vitrification method under field conditions. Blastocysts in different developmental stages were transferred to recipient cows either fresh (n = 140) or warmed after vitrification (n = 138). The pregnancy rates obtained for fresh embryos were 46.15% (initial blastocyst), 46.93% (blastocyst) and 50.0% (expanded blastocyst) at 35 days post-fertilization, and 43.58% (initial blastocyst), 46.93% (blastocyst) and 50.0% (expanded blastocyst) at 60 days. The pregnancy rates after embryo vitrification were 35.0% (initial blastocyst), 42.30% (blastocyst) and 43.47% (expanded blastocyst) at 35 days post-fertilization, and 32.50% (initial blastocyst), 38.46% (blastocyst) and 43.47% (expanded blastocyst) at 60 days. Embryo vitrification or blastocyst developmental stage did not affect pregnancy rates or incidence of embryonic death. In conclusion, vitrification of Gyr (Bos indicus) embryos under field conditions is an efficient method that can be implemented to use surplus in vitro produced embryos without affecting pregnancy rates.