Sexually active male goats stimulate the endocrine and sexual activities of other males in seasonal sexual rest through the “buck-to-buck effect”

International audienceMale goats rendered sexually active by exposure to a photoperiodic treatment are more efficient than untreated goats in stimulating LH secretion and ovulation in seasonally anestrous goats. This phenomenon is called the "male effect." Here, we determined whether sexually active bucks are able to stimulate the endocrine and sexual activities of other bucks in seasonal sexual rest through the phenomenon that we called the "buck-to-buck effect." We used bucks rendered sexually active (SA) during sexual rest by exposure to 2.5 mo of artificial long days (16 h of light per d) and untreated, sexually inactive (SI) bucks. In Experiment 1, we determined the short-term (21 d) LH and testosterone responses of sexually inactive bucks joined with a SA or SI buck. In Experiment 2, we determined the long-term (60 d) testosterone and sexual behavior responses of sexually inactive bucks joined with 2 SA or SI bucks. In Experiment 3, we determined the efficacy of bucks initially exposed to the buckto-buck effect, the SABB bucks, to thereafter induce a "classical" male effect in seasonally anestrous goats. In Experiments 1 and 2, there was an interaction between time and groups in LH and testosterone plasma concentrations (P 0.05). We concluded that the endocrine and sexual activities of bucks during sexual rest can be stimulated by SA bucks. In addition, SABB bucks are able to stimulate the reproductive activity of seasonally anestrous goats