Comparison of embryo developmental rates in Nguni, Bonsmara and Boran beef cattle breeds following in vitro fertilization and artificial insemination

The aim of this study was to compare the embryonic developmental rates in the Southern African cattle breeds. To do this, cryopreserved semen straws from Nguni, Bonsmara, and Boran bulls were thawed at 38°C and evaluated for sperm motility characteristics using Sperm Class Analyser (SCA). The fertilizing ability of frozen/thawed sperm was evaluated by performing artificial insemination (AI) and in vitro fertilization (IVF). For AI, superovulated cows were inseminated with frozen/thawed semen and then further evaluated for embryo development. For IVF, oocytes from the respective cows were retrieved using ovum pickup, and then matured. Following maturation, oocytes were co-incubated with semen for 6 h. In the Nguni breeds, the IVF method of embryo production was mildly superior to the in vivo method at the morula stage while the Bonsmara breed revealed the opposite effect at both the morula and blastocyst stages. In the Boran breed, the IVF method was highly superior with the in vivo method at the 8-cell stage while the opposite effect was observed at the blastocyst stage of embryonic development. This study suggests that the Boran breed is less susceptible to loss of embryonic development as compared to the Nguni and Bonsmara breeds.   Key words: Nguni, Bonsmara, Boran, embryo, beef breeds, motility, artificial insemination, in vitro fertilization.