Ed Squires, PhD, an honorary Diplomate in the American College of Theriogenology (reproduction), of Colorado State University, presented a lecture at the 2003 American Association of Equine Practitioners' convention on a simplified strategy for insemination of mares with frozen semen.

Squires said the perception in the industry is that mares must be examined four to six times per day to use frozen semen successfully. He said the reasons for frequent examination are because limited semen is made available and the desire to breed as close to ovulation as possible. If multiple doses of semen are available, mares could be examined once a day and treated identically to mares bred with cooled semen.

Perceived negatives to using frozen semen are that it is usually sold by the dose, it can be difficult to get, and it is often expensive if imported, he noted. There is also concern about uterine inflammation with multiple insemination doses with frozen semen and reduced fertility if mares are not bred close to ovulation. Therefore, there is a need to have a better method for breeding with frozen semen.

When frozen semen was first introduced, pregnancies were achieved by  checking the mare frequently each day and breeding with a single dose of semen as close to ovulation as possible. Therefore, this was adopted as standard operating procedure, said Squires. Veterinarians checked a mare every six hours once she was in heat and had been given hCG (human chorionic gonadotropin) or Ovuplant (deslorelin)