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

Author: K.C. Lehloenya, J.P.C. Greyling, L.M.J. Schwalbach and S. Grobler
Year: 2006
Issue: 5
Volume: 36
Page: 30 - 33

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, embryo, GnRH agonist, MOET, oestrous synchronisation, pFSH, superovulation
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