The ovarian response and embryo recovery rate in Boer goat does following different superovulation protocols, during the breeding season

摘要

Twenty-four Boer goat does were used to compare three superovulation protocols, with 8 does allocated per treatment during the natural breeding season. In Group 1 (Day 0 protocol), the oestrous cycles of does were synchronised for 7 days with CIDR's and injected PGF2l at CIDR insertion. Does were then superovulated with pFSH in 7 dosages at 12h intervals, starting 88h following CIDR removal. Concurrently with the 6th dosage, does were injected PGF2l. Cervical inseminations were performed 24h and 36h following the last superovulatory treatment. For Groups 2 and 3, the oestrous cycles of the does were also synchronised for 17 days using CIDR's. On day 14 of CIDR insertion, Group 2 does were injected with PGF2l. A superovulation treatment similar to Group 1 was administered in Groups 2 and 3, starting 48h before CIDR removal. All does in these groups were also cervically inseminated with fresh undiluted Boer goat semen 24h and 36h following CIDR withdrawal. Embryos from all 3 treatment groups were flushed on day 6 following AI. Does in Group 1 responded to the short oestrous synchronisation protocol before the administration of a superovulation treatment (71.4% response), with time to onset of oestrus of 37.2pl0.7h and duration of an induced oestrous period of 36.4pl0.5h being recorded. Following superovulation only two does exhibited signs of oestrus in Group 1, while Groups 2 and 3 exhibited a 100% oestrous response. Groups 1 and 2 recorded similar intervals to the onset and durations of the induced oestrous period. The number of ovulations per donor was significantly lower in Group 1 (4.0pl0.7), compared to Groups 2 and 3 (14.5pl0.6 and 16.5pl0.8, respectively), with no significant difference between Groups 2 and 3. The Day 0 protocol (Group 1) also resulted into a significantly lower total number of structures recovered, compared to Group 3. Groups 2 and 3 recorded a relatively similar number of structures recovered. The number of embryos recovered was significantly lower (P <0.01) in Group 1 (0.2pl0.1) than in Group 2 (13.2pl0.5) and Group 3 (11.5pl1.1), with the mean number of unfertilised ova and degenerated embryos being similar for all 3 treatment groups. Groups 2 and 3 also produced a similar number of transferable embryos. The blood progesterone concentrations followed a similar trend in the 3 treated groups, from CIDR insertion to embryo flushing. However, the mean serum progesterone concentration was significantly lower on day 4 in the Day 0 group, compared to Groups 2 and 3. The inclusion of PGF2l treatment in the superovulation protocol for Boer goats had no beneficial effect, while the Day 0 protocol engaged in this trial, resulted in a lower superovulation response. Further research is warranted, focusing on synchronisation, time when initiating superovulatory treatment and AI to improve the embryo yield in goats.