Comparative efficacy of BioRelease Deslorelin® injection for induction of ovulation in oestrus mares: a field study

Objective To investigate the comparative efficacy of BioRelease Deslorelin® ( BRD ) and Ovuplant® for induction of ovulation in cyclic mares in Australia. Methods Ovarian follicular activity of 60 mares for a total of 95 cycles was monitored by ultrasonography until they developed a follicle ≥30 mm and a uterine oedema pattern of 3. Mares were then randomly allocated to one of three treatment groups: (1) treatment with 1.25 mg BRD , (2) a single Ovuplant pellet or (3) 1 mL compound sodium lactate control. Follicular activity was monitored with ultrasonography every 12 h until ovulation was detected or for at least 5 days post treatment. The injection site on each mare was monitored for reaction for a minimum of 5 days post treatment. Results There was no difference in the percentage of mares ovulating within 48 h when treated with BRD (93.75%) compared with Ovuplant (87.09%). Treatment with both ovulating agents significantly decreased the time to ovulation compared with control mares (P < 0.00005). More mares had injection site reactions with Ovuplant (64.5%) treatment compared with BRD (15.6%) or control mares (0%) (P < 0.00005). Conclusions Treatment of mares with 1.25 mg BRD when there is a follicle ≥30 mm and uterine oedema pattern of 3 is as effective as treatment with Ovuplant.