Sexually active bucks are efficient to stimulate female ovulatory activity during the anestrous season also under temperate latitudes
Résumé
Goats are seasonal breeders and photoperiod is the main cue controlling the onset and offset of the breeding season. Nevertheless introducing a sexually active buck in a group of females during anestrous can stimulate their reproductive function and induce ovulation. This “male-effect” is very efficient under subtropical latitudes, when using sexually active males previously stimulated by a photoperiodic treatment. However, there is less evidence of its feasibility under temperate latitudes where the more important variation in day length could be responsible for a stronger inhibition of female sexual activity. The aim of this study was therefore to determine whether intense sexual activity can be induced in Alpine bucks during the non-breeding season by a long-day treatment under temperate latitude and if these males could be used to produce an efficient male-effect. Bucks were divided in two groups, one submitted to a photoperiodic treatment from November 1st to January 15th and then switched to natural photoperiod, while the other group remained entirely under the natural photoperiod. At the end of March, bucks were used to stimulate anestrous does continuously for 15 days. We showed that (a) light treatment was efficient to induce an increase of sexual activity in bucks and (b) that the introduction of stimulated bucks among females induced a significantly higher proportion of ovulation in anestrous does than control bucks (87% vs 14%). Our results indicate that under temperate latitudes induction of ovulation in females during the anestrous season is feasible using bucks treated with long-days during winter.