CONTROL OF OVULATION IN THE MARE USING A SUBCUTANEOUS IMPLANT - EFFECTS ON STALLION USE

Ovuplant(TM) (Fort Dodge Laboratories, Fort Dodge, IA) is a subcutane ous implant for the short-term release of 2.1 mg of the potent GnRH an alog deslorelin. When used in estral mares with a lead follicle > 30 m m in diameter, ovulation occurs within 48 hours in most mares. In this study, Ovuplant was used strategically on two Thoroughbred farms with three stallions to space breedings close to ovulations and by this to conserve the breeding use of the stallions in 47 mares receiving 51 t reatments; 67 untreated mares served as contemporary controls. Treatme nt resulted in ovulations within 48 hours in 94.1% of the mares, with a mean interval to ovulation of 42.4 hours (range: 24 to 96 hours). Tr eatment reduced the number of breedings per estrus and far the entire season to 1.16 and 1.36 per mare vs. 1.40 and 3.58 in untreated contro ls (P < 0.05), and the number of estrus periods for the season (1.17 v s. 2.57; P < 0.05). Early pregnancy rates for treated and untreated ma res were 68.2% vs. 64.1% at the treatment estrus, or a contemporary es trus in controls. Early pregnancy rates from breedings at two subseque nt estrous periods were 88.6 and 82.8% for treated and untreated mares , respectively.