title: The reproductive performance of Thoroughbred mares treated with intravaginal progesterone at the start of the breeding season.
abstract: The objective of this study was to investigate the effects of intravaginal progesterone on the reproductive performance of transitional Thoroughbred mares on commercial stud farms. Two hundred twenty-seven (227) non-lactating transitional Thoroughbred mares aged between 4 and 18 y (mean 9.4 ± 3.2 y) located on three stud farms in the Waikato region of New Zealand were used in the study performed during four consecutive breeding seasons (2007-10). Mares were age-matched in pairs and either treated with an intravaginal progesterone releasing device (Cue-Mare, 1.72 g progesterone, 10% w/w) for up to 10 d (Treated; n = 126) or left untreated (Control; n = 101). In both groups, 1,667 iu of hCG was given IV when an ovarian follicle ≥35 mm was detected (in conjunction with estrous behavior) and each mare was bred by natural service. Treated mares were served earlier in the breeding season (mean ± SD interval to first service was 13.9 ± 3.0 vs 26.7 ± 13.2 d for Treated and Control groups, respectively; P < 0.001). In the Treated and Control groups, 95.2 and 42.6% of mares were served within the first 21 d of the season (P < 0.001). Treated mares conceived earlier in the breeding season (mean number of days to conception 37.5 ± 14.2 vs 50.8 ± 21.3 d, P = 0.01). There was no difference between groups in the first service pregnancy rates (53.9 and 50.5% for Treated and Control mares, P = 0.89). Treatment with an intravaginal device increased the number of mares conceiving by the end of the breeding season (91.3 vs 82.3% for Treated and Control groups, P = 0.04). Therefore, this treatment protocol appeared to offer a convenient, economical and reliable method for managing transitional mares on commercial Thoroughbred stud farms.
authors.affiliation: Matamata Veterinary Services, Ltd, 26 Tainui Street, Matamata, New Zealand. dhanlon@matavet.co.nz
authors.forename: D W
authors.initials: DW
authors.lastname: Hanlon
authors.forename: E C
authors.initials: EC
authors.lastname: Firth
mesh_terms: D000282:Administration, Intravaginal; D000818:Animals; D001947:Breeding / Q000379:methods*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D005260:Female; D005306:Fertilization / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D008297:Male; D009520:New Zealand; D011247:Pregnancy; D018873:Pregnancy Rate; D011374:Progesterone / Q000008:administration & dosage*; D012098:Reproduction / Q000187:drug effects* / Q000502:physiology*; D012621:Seasons
chemical_list: D006063:Chorionic Gonadotropin; D011374:Progesterone