Several studies have reported the hormonal changes occurring during the estrous cycle in the bitch. In this species estrus is characterised by a sharp progesterone increase, because of preovulatory luteinization of mature follicles, and a decrease of estrogens. Even if it has been reported that administration of testosterone propionate to ovariectomised bitches can induce sexual receptiveness (Olson et al., 1984), little is known about the role of androgens in the sexual behaviour of the estrous bitch. The aim of this study was to increase the knowledge concerning sexual steroids changes occurring during estrus in the bitch, focusing on changes associated with the beginning and the end of sexual receptiveness, in the purpose of mating management.
