375 PERFORMANCE OF DIFFERENT BOVINE BREEDS ON IN VITRO COMMERCIAL EMBRYO PRODUCTION USING SEX-SORTED SEMEN

Abstract

Commercial bovine in vitro production (IVP) systems using sex-sorted semen, instead of the invasive technique involving embryo biopsy followed by PCR, have a superior influence on embryo production rates. However, due to damage from flow cytometric procedures and cryopreservation, blastocyst rates using sex-sorted semen remain lower than from conventional non-sorted semen. The aim of this study was to describe embryo production rates using sex-sorted semen during the past year in different bovine breeds. Cumulus oocyte complexes obtained by ovum pickup (OPU) from high genetic merit donor cows were matured (TCM-199, supplemented with FCS, LH, FSH, estradiol, pyruvate, and antibiotics) for 24 h and fertilized (Fert-TALP supplemented with BSA, phenylalanine, and heparin) for 18-22 h (Day 0) in vitro. Frozen sex-sorted semen samples from different bulls were thawed at 35°C for 30 s in a water bath and then selected by centrifugation at 800 g on discontinuous Percoll™ gradients (45 : 90%). Presumptive zygotes were transferred to culture medium (SOFaa supplemented with BSA and FCS) on Day 1 and blastocyst rate was evaluated on Day 7. During the past year, sex-sorted semen was used more frequently on Bos taurus (Holstein), Bos indicus (Gyr), and crossbred (Gyrolando) milk cattle than in meat breeds (Nelore, Guzera, and Brahman). The large numbers of oocytes routinely recovered in Nelore cows could be attributed to the female valorization in the market due to high potential in new generations and repositioning of genetic value. The effect of subspecies (Bos taurus taurus and Bos taurus indicus) could be also observed in blastocyst rate, with better results than Holstein, showing the same tendency when conventional (non-sexed) semen is used. Embryo production in Brahman and Nelore with sex-sorted semen was lower than with conventional (non-sexed) semen, probably due to damage to the sperm during the sorting process, thereby changing patterns of fertilization, involving the acrosome reaction, for example. This points to the need for more studies on cellular integrity during the sorting process as well improvement of IVP procedures with sex-sorted semen. Table 1.Embryo production rates according to different bovine breeds