With the advanced reproductive techniques available today, breeders can help even stallions with poor-quality or limited sperm produce offspring. One method is called intracytoplasmic sperm injection (ICSI)–a form of in vitro (in the lab) fertilization where a single sperm is injected directly into an egg. However, this procedure comes with a high price tag because for a variety of logistical reasons it typically requires two mares: one to donate the oocytes (eggs) and one (called a recipient mare) to carry the embryo to term. A Colorado State University (CSU) research team recently set out to determine whether they could establish a viable pregnancy by implanting the ICSI-produced embryo back into the oocyte donor mare.

Elaine M. Carnevale, MS, DVM, PhD, associate professor at CSU's Animal Reproduction and Biotechnology Laboratory, presented the team’s findings at the 2013 American Association of Equine Practitioners’ Convention, held Dec. 7-11in Nashville, Tenn. She explained that owners use separate donor and recipient mares when the donor mare has reproductive tract problems or if they desire more than one foal from the donor mare in a season. Under some conditions, however, such as when ICSI is being performed because of a stallion's limited or poor semen, it might be advantageous to use the same mare as both egg donor and embryo recipient. The challenge lies in timing the development of the embryo in the lab with the mare’s reproductive cycle.

In their study, the team collected 12 oocytes from nine mares and used ICSI to fertilize them. Carnevale said eight embryos developed to the blastocyst stage of embryonic development (which takes about six to seven days) before the team transferred them back into the donor mare’s uterus. Five pregnancies resulted from these embryos, a very good success rate, Carnevale said.