Removal of deslorelin (Ovuplant) implant 48 h after administration results in normal interovulatory intervals in mares.
Deslorelin implants, approved for use in inducing ovulation in mares, have been associated with prolonged interovulatory intervals in some mares. Administration of prostaglandins in the diestrous period, following a deslorelin-induced ovulation, has been reported to increase the incidence of delayed ovulations. The goals of the present study were: (1) to determine the percentage of mares given deslorelin that experience delayed ovulations with or without subsequent prostaglandin treatment, and (2) to determine if removal of the implant 48 h after administration would effect the interval to subsequent ovulation. We considered interovulatory intervals to be prolonged if they were greater than the mean +/- 2 standard deviation (S.D.) of the control group in study 1 and the hCG group in study 2. In study 1, we retrospectively reviewed reproduction records for 278 mares. We either allowed the mare to ovulate spontaneously or induced ovulation using deslorelin acetate implants or hCG. We administered prostaglandin intramuscularly, 5-9 days after ovulation in selected mares in each group. A higher percentage of mares which were induced to ovulate with deslorelin and given prostaglandins had a prolonged interovulatory interval (23.5%; n = 16), as compared to deslorelin-treated mares that did not receive prostaglandins (11.1%; n = 5). In study 2, we induced ovulation in mares with hCG (n = 47), a subcutaneous deslorelin implant via an implanting device provided by the manufacturer (n = 28), or a deslorelin implant via an incision in the neck (n = 43) and we removed the implant 48 h after administration. We administered prostaglandin to all mares 5-9 days after ovulation. In study 2, mares from which the implant was removed had a normal ovulation rate and none had a prolonged interval to ovulation. Administration of prostaglandin after deslorelin treatment was associated with a longer interval from luteolysis to ovulation than that found in mares not treated with deslorelin. Prostaglandin administration during diestrus may have exacerbated the increased interval to ovulation in deslorelin-treated mares. We hypothesize that prolonged secretion of deslorelin from the implant was responsible for the extended interovulatory intervals.
McCue
P M
PM
Animal Reproduction and Biotechnology Laboratory, Colorado State University, Ft Collins 80523, USA. patrick.mccue@colostate.edu
Farquhar
V J
VJ
Carnevale
E M
EM
Squires
E L
EL
D000818:Animals; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D003008:Cloprostenol / Q000008:administration & dosage; D004343:Drug Implants; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D006736:Horses; D006801:Humans; D010060:Ovulation; D010062:Ovulation Induction / Q000662:veterinary; D012189:Retrospective Studies; D013997:Time Factors; D017329:Triptorelin Pamoate / Q000031:analogs & derivatives
D006063:Chorionic Gonadotropin; D004343:Drug Implants; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; D003008:Cloprostenol; C066438:deslorelin