Protocols, problems and pitfalls with fresh, chilled and frozen semen

The longevity of equine semen once thawed, and therefore its viability in the mare is short lived, the general assumption is that for the semen of most stallions, its longevity in the mare is in the order of 12 h or less. While it would be reasonable to assume that the highest quality semen would have the longest longevity, it is possible that poorer quality semen has the shortest longevity and with such semen it may be better to have the oocyte waiting for the sperm than the reverse. A mare-examination protocol of no more than every 6 h ensures insemination as close as possible to ovulation. Timed insemination protocols have been suggested by giving an ovulation inducing agent about 42–48 h in advance of a convenient time to inseminate. Insemination may then wait until ovulation has occurred or when the follicle is plainly very close to ovulation. Not all mares respond reliably to human chorionic gonadotropin (hCG) because either the drug was given too early or due to hCG antibodies. The use of a gonadotropinreleasing hormone (GnRH) agonists should avoid this. The decision when to give the ovulation-inducing drug will be determined by a number of factors. Although the majority of follicles grow at about 4 mm/day and ovulated from 40 to 45 mm, ovulations from follicles of 30 mm or less are not uncommon ...