Efficacy Of Lyophilized Deslorelin On Induction Of Ovulation In Mares

Abstract

Options for induction of ovulation in mares include human chorionic gonadotropin (hCG) and potent agonists of gonadotropin-releasing hormone (GnRH) such as deslorelin acetate. When no commercially produced GnRH agonists are available, GnRH agonists can be acquired through compounding pharmacies. The objective of this project was to evaluate the efficacy of lyophilized deslorelin acetate to induce ovulation and to determine if the efficacy was adversely affected after 12 months of storage. Mares in estrus were administered 1.5 mg of deslorelin (lyophilized- 2009, lyophilized- 2010, or aqueous deslorelin) as an intramuscular injection once a follicle  35 mm was detected in the presence of uterine edema. Mares were subsequently examined once per day to determine the day of ovulation. A total of 66 mares were administered lyophilized deslorelin in 2009 and 135 mares were treated in 2010 with lyophilized deslorelin from the same initial lot stored for 12 months. Thirty mares were administered liquid suspension deslorelin in 2010. There was no significant difference in mean days to ovulation among treatment groups with majority of treated mares (89.6%) ovulating within 48 hours after deslorelin administration. Results of this study indicate that lyophilized deslorelin stored for 12 months, reconstituted in sterile saline, is equally as effective at inducing a timed ovulation in estrual mares as deslorelin in a liquid suspension. In conclusion, non-reconstituted vials of lyophilized deslorelin may be stored for at least 12 months without a significant loss in efficacy.