Fertility of Frozen Semen

Below are result of inseminating frozen semen as determined by pregnancy rates at various days after breeding. The different days are done in case there is embryonic loss occuring. The results demonstrate that although frozen semen is slightly less fertile than fresh semen, it is not that bad. The insemination prior to ovulation was better than inseminating after ovulation. To achieve insemination this close to ovulation, it is neccessary to ultrasound or palpate mares every 6 hours starting 24 hours after HCG administration. These conditions almost always require the mare be housed at a veterinary clinic inorder for the veterinarian to have ready access to the mare.

More recently, a double insemination procedure has been used by UW-Madison and other labs. In this procedure, Mares are inseminated 24 hours after ovulation induction with HCG or Desorelin, checked for ovulation with ultrasound at 36 hours and inseminated again if not ovulated. Alternatively, mares are inseminated at both 24 and 36 after ovulation induction and verified to have ovulated at 48 hours after ovulation induction. These approaches minimize the number of times a mare is required to have an ultrasound exam. From personal experience, the checking of mares every 6 hours is quite exhausting for the Veterinarian or ultrasound technician.

Note that all procedures for using frozen semen require insemination close to the time of ovulation.