ABSTRACT
Embryo transfer could obviously increase the rate of production of progeny from any such desirable pair. Two major barriers exist to limit the use of embryo transfer in horses. First, and perhaps foremost, the registration authorities for most pure breeds of horses throughout the world will not permit the entry into their respective stud books of progeny which have resulted from embryo transfer. Secondly, and as will be discussed in more detail later, there does not yet exist an efficient method for inducing superovulation in the mare. The mare is a seasonally polyestrous animal with a distinct breeding season during spring, summer, and early autumn. Pituitary gonadotrophin release patterns in the cycling mare differ markedly from those shown by the other large domestic species. Donor mares are injected with 250 µg of the prostaglandin analogue, chloprostenol immediately after undergoing nonsurgical embryo recovery on day 7 or 8 after ovulation.
