Effect of season on the superovulatory response in Boer goat does

• Published in: Small ruminant research 2008-08, Vol.78 (1), p.74-79
• Main Authors: Lehloenya, K.C., Greyling, J.P.C., Grobler, S.
• Format: Article
• Language: English
• Subjects: Boer; Boer goat; breeding season; controlled internal drug release devices; embryo (animal); embryo transfer; embryogenesis; estrus; females; goats; gonadotropin-releasing hormone; multiple ovulation and embryo transfer program; ova; Ovulation rate; Season; seasonal variation; Superovulation
• ISSN: 0921-4488; 1879-0941
• DOI: 10.1016/j.smallrumres.2008.05.003

This study was conducted to evaluate the effect of season on the superovulatory ovarian response and embryo recovery rate in Boer goat does. Twenty mature does (mean body weight of 55 kg) were synchronised for oestrus with the aid of CIDR devices for a period of 17 days and superovulated with pFSH (Folltropin ®-Vetrepharm) during the natural breeding season ( n = 9) and non-breeding season ( n = 11). The superovulation treatment entailed a total dose of 200 mg pFSH/doe given i.m. in 7 dosages at 12 h intervals, starting 48 h prior to CIDR removal (the first dose being 50 mg and all others 25 mg). Does were observed for signs of oestrous behaviour 3 times daily at 8 h intervals following CIDR withdrawal with the aid of teaser bucks to determine the onset and duration of the induced oestrous period. Cervical inseminations with 0.1 ml fresh undiluted semen were performed 36 and 48 h following CIDR removal and the embryos surgically flushed 6 days following the second AI. Recovered structures (ova and embryos) were microscopically evaluated and classified according to their morphology. The total number of structures in terms of unfertilised ova, fertilised ova, degenerated embryos and transferable embryos from each doe flushed was recorded. All the donor does exhibited oestrus during the breeding and non-breeding season with the mean period to the onset of oestrus (24.9 ± 4.8 h) being significantly ( P < 0.05) earlier during the natural breeding season, compared to the non-breeding season (30.5 ± 9.1 h). The duration of the induced oestrous period was also significantly ( P < 0.05) longer during the natural breeding season (24.0 ± 5.7 h) than the non-breeding season (18.2 ± 3.7 h). The mean ovulation rate per donor, total number of structures and embryos recovered per donor did not differ between seasons. The mean number of unfertilised ova per doe was significantly ( P < 0.05) higher during the non-breeding season (3.3 ± 2.8), compared to the natural breeding season (0.9 ± 2.4). The total number of degenerated embryos and transferable embryos however, did not differ between seasons. Season as such had an effect on the onset and duration of the induced oestrous period; however, it did not affect the oestrous response. Therefore, it would seem that superovulation in the Boer goats is warranted, irrespective of season.