The effectiveness and efficiency of ovulation induction agents in mares

Study 1: A retrospective analysis of the effects of hCG and deslorelin on the reproductive efficiency on two commercial horse farms. Reproductive data from two central Illinois horse farms was analyzed to compare the effectiveness of hCG (Chlorulon™) and a sustained release implant formulation of deslorelin (Ovuplant™) for inducing ovulation and their overall effect on reproductive efficiency. Data were collected over 3 consecutive years, from 1999-2001; a total of 1422 cycles were examined from 658 mares. Of the 1422 cycles examined, 383 were treated with hCG, 451 with deslorelin and 583 cycles were untreated. Mares in this study were over 2.1 times more likely to become pregnant if ovulation was induced (p45 mm (p=.001). Time from treatment to ovulation was affected by follicle size at time of treatment and by treatment given. When treatment was given at follicle sizes from 35 mm-39 mm, time to ovulation was shorter with deslorelin (2.02 days) than with hCG (2.68days) (p=.000). The number of palpations was not decreased by the use of ovulation induction but follicle size at administration and day of administration showed a positive effect on reducing the number of palpations. Administration of either agent at the first breeding examination when follicles were less than 35 mm in diameter decreased the number of palpations per cycle by one in comparison to non-treated mares. (p=.009) Fewer artificial inseminations per cycle were performed using deslorelin for follicles between 35 and 44 mm compared no treatment [35-39 mm follicles (p=.000): deslorelin 1.21 AI, untreated 1.39 AI; 40-44 mm follicles(p=.000): deslorelin 1.16 AI, untreated 1.48 AI] . Administration of either hCG or deslorelin to mares possessing a <35 mm follicle at the first breeding exam decreased the number of artificial inseminations required per cycle by 1 (p=.001). Both agents performed equally well at inducing ovulation within 48 hours of administration. Deslorelin appeared more consistent in decreasing the days to ovulation in comparison to hCG . Deslorelin decreased the days to ovulation at