Abstract
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.
Highlights
The success of the Southern African regional beef industries depends on its indigenous cattle beef breeds for their sustainability and competitiveness in the global stage (Morgan et al, 1991; Mckenna et al, 2002; Scholtz and Theunissen, 2010)
Hoechst 33342 staining of developing embryo revealed clear developmental stages into the 2-4 cells to blastocyst stages of embryonic development (Figure 1)
In the Boran breed, the in vitro method of embryo production was significantly superior to the in vivo embryo production method at the 8-cell stage of development; the in vivo method became superior at the blastocyst stage of development (Figure 4)
Summary
The success of the Southern African regional beef industries depends on its indigenous cattle beef breeds for their sustainability and competitiveness in the global stage (Morgan et al, 1991; Mckenna et al, 2002; Scholtz and Theunissen, 2010). Mapeka et al 963 with carcass marbling and meat tenderness which are favourable to consumers (Scholtz, 1988; Strydom et al, 2008; Scholtz and Theunissen, 2010). All these breeds possess survival traits that are suitable for local conditions including tolerance to diseases and harsh environmental conditions. They possess superior growth and reproductive performance and are outstanding beef breeds (Strydom et al, 2008). The efficiency of in vivo fertilization has become a pressing issue worth investigating in our local beef breeds
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