People have successfully shortened or lengthened mares’ estrous cycles for decades, but it’s a much taller order to induce cycling in a mare that’s not cycling at all. However, researchers recently reported good success with inducing ovulation in winter anestrous (noncycling) mares via a new hormone therapy regimen at the 2011 American Association of Equine Practitioners convention held Nov. 18-22 in San Antonio, Texas.

Veterinarians and owners have traditionally used artificial lights  to  stimulate mares to ovulate earlier in year (February) instead of waiting until the onset of the natural or physiologic breeding season (April). People have also successfully shortened or  lengthened estrous cycles to synchronize donor and recipient mares for oocyte or embryo transfer.

Researchers at Colorado State University, the University of Kentucky, and the University of California, Davis, have taken this process one step further by using recombinant equine follicle-stimulating hormone (reFSH) to induce follicle development and subsequent ovulation in deep anestrus mares (the stage they’re generally in midwinter).

The hormone eFSH has been used in the past to stimulate donor mares’ ovaries to increase the number of ovulations (i.e., superovulation) and thereby increase the number of embryos that may be recovered during  one cycle.

"Recombinant equine FSH is a synthetic version of equine FSH in that it is produced in a laboratory," explained presenter Pat McCue, DVM, PhD, Dipl. ACT, professor in the Department of Clinical Sciences at Colorado State..  " ‘Regular’ eq