Use of deslorelin short-term implants to induce ovulation in cycling mares during three consecutive estrous cycles |
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| Institution: | 1. Animal Reproduction and Biotechnology Laboratory, Department of Physiology, Colorado State University, Fort Collins, CO 80523, USA;2. Wolfgang Jöchle Association, Inc., Denville, NJ 07834, USA;3. Peptide Technology, Ltd., Dee Why, N.S.W. 2099, Australia;1. Animal Health Trust, Newmarket, UK;2. Davies Veterinary Specialists, Higham Gobion, Hitchin, UK;3. Taylor Monroe, Little Downham, Ely, UK;1. CIISA, Faculty of Veterinary Medicine, University of Lisbon, Lisbon, Portugal;2. Department of Animal Science, Coimbra College of Agriculture, Coimbra, Portugal;3. Department of Reproductive Immunology and Pathology, Institute of Animal Reproduction and Food Research of PAS, Olsztyn, Poland;1. Department of Large Animal Clinics, Equine Sports Medicine and Surgery, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil;2. Department of Large Animal Clinics, College of Veterinary Medicine, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil;1. Taylor Monroe, Gravel Head Farm, Little Downham, UK;2. Bell Equine Veterinary Clinic, BEVC, Maidstone, UK;3. Clinical Veterinary Medicine, University of Cambridge, Cambridge, UK;4. Isle Veterinary Clinic, Ely, UK;5. Equine Referral Hospital, Royal Veterinary College, Hatfield, UK;1. Reproduction Laboratory, Maxwell H. Gluck Equine Research, Department of Veterinary Science, University of Kentucky, Lexington KY 40546-0099, USA;2. Faculdade de Medicina Veterinária e Zootecnia, UNESP–Universidade Estadual Paulista, Departamento de Reprodução Animal e Radiologia Veterinária, Botucatu, São Paulo, CEP: 18618-970, Brazil |
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| Abstract: | Alternatives to human chorionic gonadotropin (hCG) for inducing ovulation in cycling mares over several consecutive cycles were explored. Placebo, one, three or five short-term implants each containing 2.2 mg of gonadotropin-releasing hormone (GnRH) analogue (deslorelin) were administered to cycling mares after identification of a follicle over 30 mm. Mares were treated over three consecutive cycles, and artificially inseminated during the third cycle only. Serum was assayed for concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and progesterone during each cycle. All deslorelin doses decreased the interval to ovulation (4.0 days, 2.6 days, 2.4 days and 2.0 days), increased the proportion of mares ovulating within 48 h (20.0%, 83.3%, 73.3% and 85.7%), and decreased the diameter of the largest follicle at ovulation (45.8 mm, 38.0 mm, 41.0 mm and 37.2 mm) for the placebo, 2.2 mg, 6.6 mg and 11.0 mg groups, respectively (P < 0.05). The interovulatory interval was lengthened in the 11.0 mg group compared with all other groups (21.2 days, 21.8 days, 26.4 days and 32.7 days for the placebo, 2.2 mg, 6.6 mg and 11.0 mg groups, respectively, P < 0.05). No differences (P > 0.05) were detected in serum concentrations of progesterone or pregnancy rate among the groups. Cycle number had no effect (P > 0.05) on the reproductive parameters or serum concentrations of progesterone. Concentrations of LH were higher in Cycle 3 in the 6.6 mg and 11.0 mg groups, and FSH concentrations were decreased in Cycles 2 and 3 in treated mares. Deslorelin was efficacious for inducing ovulation in cycling mares with no diminished activity over three consecutive cycles. However, ovarian suppression and changes in serum concentrations of gonadotropins were noted at higher doses. |
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