hCG is more effective than the GnRH agonist buserelin for inducing the first ovulation of the breeding season in mares.

These results demonstrate that hCG was more effective than GnRHa for inducing ovulation in the first cycle after winter anoestrus. Uterine oedema and behavioural signs of oestrus, for at least three days before the treatment, were predictors for a positive response to ovulation induction.