Superovulatory response in Boer goats pre-treated with a GnRH agonist outside the natural breeding season

Abstract

The aim of this study was to evaluate the ovarian response and embryo recovery rates in Boer goat does superovulated with pFSH following a pre-treatment with a GnRH agonist (GnRHa) outside the natural breeding season. Oestrus was synchronised in 22 does with CIDR\'s for 17 days, and these were superovulated with a total dose of 200 mg pFSH/doe administered i.m. in seven dosages, at 12 h intervals, starting 48 h prior to CIDR removal (the first dose being 50 mg and all others 30 mg each). Half of the does (n = 11; treatment group) received GnRHa (Lucrin®) for seven days, starting on day 7 of CIDR insertion, while the other half (n = 11; control group) received no GnRHa. Cervical inseminations with fresh undiluted semen were performed 36 h and 48 h following CIDR removal and the embryos surgically flushed six days after the second AI. The oestrous response, onset- and duration of the induced oestrous period did not differ significantly between groups. There were also no significant differences between pFSH (21.3 ± 5.9) and pFSH/GnRHa (16.1 ± 7.0) treatments, with respect to the mean ovulation rate per donor. However, the mean total number of structures recovered (unfertilised ova and embryos) per doe flushed and the fertilisation rates (%) were significantly lower in the pFSH/GnRHa treated does (12.7 ± 6.0; 11.5 ± 5.3; 81.6 ± 32.2%, respectively), compared to the control group (17.5 ± 4.5; 16.5 ± 6.1; 92.6 ± 19.6%, respectively). In addition, the mean number and percentage of transferable embryos were also significantly lower in the pFSH/GnRHa treated does (4.3 ± 4.0 and 32.7 ± 36.9%), compared to the control does (13.1 ± 5.3 and 75.2 ± 26.8%, respectively). However, no significant differences were recorded in the mean total number of unfertilised ova/doe between groups. The pFSH/GnRHa treatment resulted in a higher number of degenerated embryos per donor (6.9 ± 4.5) compared to the control (3.2 ± 4.2). The pre-treatment with a GnRHa to the pFSH superovulation protocol outside their natural breeding season seemed to be detrimental to embryo production and quality in Boer goats, and is not warranted.

Keywords: Boer goats; superovulation; oestrous synchronisation; pFSH; GnRH agonist; embryo; MOET

South African Journal of Animal Science Vol. 36 (5) 2006: pp.30-33