The Effect of Time of Insemination With Fresh Cooled Transported Semen and Natural Mating Relative to Ovulation on Pregnancy and Embryo Loss Rates in the Mare

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ContentsOne hundred and fifty-four mares were inseminated with fresh semen either during the pre- or post-ovulatory periods at different intervals relative to ovulation: 36–24 h (n = 17) and 24–0 h (n = 30) before ovulation; 0–8 h (n = 21), 8–16 h (n = 24), 16–24 h (n = 48) and 24–32 h (n = 14) h after ovulation. All mares received the same routine post-mating treatment consisting of an intrauterine infusion with 1 litre of saline and antibiotics followed 8 h later by an intravenous administration of oxytocin. Artificial inseminations (AI) from 36 h before ovulation up to 16 h post-ovulation were performed with transported cooled semen. While there was no data available for inseminations later than 16 h, data from natural mating after 16 h post-ovulation were included. Pregnancy rate (PR) of mares inseminated 36–24 h (29.4%) was significantly lower (p < 0.05) than mares inseminated 24–0 h before ovulation (60%), 0–8 h (66.7%) and 8–16 h (70.1%) post-ovulation. Embryo loss rate (ELR) was highest in mares mated 24–32 h after ovulation (75%). PR of mares mated 16–24 h post-ovulation (54.1%) did not differ significantly from any other group (p > 0.05); however, the ELR did increased markedly (34.6%) compared with inseminations before 16 h post-ovulation (<12%). At ≥30 days post-ovulation, PR of mares mated 16–24 h after ovulation (35.4%) was significantly lower than mares mated 0–16 h after ovulation (62%). Good PR with acceptable ELR can result from inseminations within 16 h of ovulation, at least with this specific post-mating routine treatment.

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