Synchronization of oestrus and ovulation by short time combined FGA, PGF2α, GnRH, eCG treatments for natural service or AI fixed-time

Two experiments were conducted in ewes in order to develop an oestrus–ovulation short time synchronization protocol based on combined FGA, PGF2α, GnRH, eCG treatments, for use in dairy sheep before natural service (Experiment 1) or for fixed-time artificial insemination (Experiment 2), during the breeding season. In Experiment 1 seventy-five non-lactating dairy ewes were subdivided into 5 treatment groups (N = 15): (1) Group Fe – control, which received FGA vaginal sponges (14 days) + eCG (Day 14); (2) Group FPe, FGA (5 days) + PGF2α (Day 5) + eCG (Day 5); (3) Group PFe, PGF2α (Day 0) + FGA (5 days) + eCG (Day 5); (4) Group PFG, PGF2α (Day 0) + FGA (5 days) + GnRH (30 h after sponge removal, s.r.); (5) Group GPe, GnRH (Day 0) + PGF2α (Day 5) + eCG (Day 5). Ewes were checked for oestrus and hand-mated. Time of ovulation was recorded by laparoscopy for 10 animals from each treatment.The percentages of female in oestrus and the interval to oestrus (h after treatment), fertility and prolificacy rate were recorded. There were no treatment differences in the percentage of females in oestrus. The interval to oestrus was earlier in Fe Group and delayed in FPe Group (P < 0.01). Ovulation time was earlier in GPe Group compared to FPe Group (P < 0.05). Fertility rates were significantly different (P < 0.05) between the PFe and the FPeG Groups compared with the PFG Group.No significant differences were observed in prolificacy among the treatments. In Experiment 2, sixty dry ewes were subdivided (N = 20) into the following three experimental treatment groups: (1) Group FP, FGA (5 days) + PGF2α (Day 5); (2) Group FPG, FGA (5 days) + PGF2α (Day 5) + GnRH (30 h s.r.); (3) Group FPeG, FGA (5 days) + PGF2α (Day 5) + eCG (Day 5) + GnRH (30 h s.r.). These were further subdivided into two groups (N = 10) corresponding to 52 and 60 h s.r. fixed-time insemination. Laparoscopic intrauterine insemination was performed with frozen semen (80 × 106 spermatozoa/dose) and ovulation time was recorded in a subgroup (N = 10). GnRH resulted in an earlier ovulation time (P < 0.05) in FPG and FPeG Groups (53.0 h vs 61.6 h). Fertility rate was higher in FPeG treated ewes inseminated at 60 h s.r. (60%, 6/10). In FP and FPG Groups fertility rates were higher following insemination at 52 h s.r. (50.0 and 40.0%).