Recombinant gonadotropins effect in stimulating follicular development in both the transitional and cyclic mare

The equine industry contributes over 39 billion dollars annually to the U.S. economy. Breeding top performance horses is a major goal of the industry. Reproductive technologies such as superovulation, embryo transfer, intra cytoplasmic sperm injection (ICSI), gamete intrafallopian transfer (GIFT) and advancing the time to the first ovulation of the year are of great benefit to the equine industry. Unique single chain recombinant equine gonadotropins [recombinant equine luteinizing hormone (reLH) and recombinat equine follicle stimulating hormone (reFSH)] have been recently developed and shown to be biologically active in vitro and in vivo. In the studies herein, the following hypothesis were tested: 1. reFSH and reLH shorten the time to ovulation during vernal transition in mares, 2. reFSH induces follicular growth and increases the number of ovulations and embryos recovered in cyclic mares and 3. reFSH followed by reLH increases the embryo to ovulation ratio and the number of embryos recovered after superovulation in cyclic mares compared to reFSH alone. Study one showed that reFSH significantly shortened the time to the first ovulation of the year compared to controls. There was also a significant increase in follicular activity, by an increase in the number of 35 mm follicles as well as an increase in ovulations compared to controls. Study two showed that the number of pre-ovulatory follicles, ovulations and embryos recovered per recovery attempt were greater in the 0.85 mg reFSH group than the control group demonstrating that efficacy of reFSH in superovulating mares. Study Three showed treatment with a lower dose of reFSH, in conjunction with reLH significantly increased the number of ovulations and embryos recovered compared to treatment with reFSH alone. This data shows that recombinant equine gonadotropins can drive ovarian activity in both transitional and cyclic mares. A treatment regime using reFSH and reLH, could increase the number of fertile ovulations and viable eggs for assited reproductive technologies. This would increase reproductive efficeny and decrease the time and money required for a successful pregnancy.