RESPONSE TO THE MALE EFECT IN NUBIAN AND ALPINE GOATS MAINTAINED UNDER TROPICAL PHOTOPERIOD

Abstract

In order to determine the extent of response to the male effect in two breed of goats, previously observed to express a similar pattern of reproductive seasonality under tropical photoperiod (22°N), 17 Nubian and 15 Alpine female goats were exposed to sexual active males at May 15th. A higher proportion of Nubian vs. Alpine does ovulated in response to the male effect (76.5 vs 33.3%; P<0.02). Two peaks of P4 at 4 and 19 day after male introduction were observed, being more evident in Nubian does. Eight Nubian does showed P4 increases >0.5 ng ml-1 within the first four days after male introduction, whilst Alpine does maintained basal P4 levels during the same period (≤0.04 ng ml-1). The higher proportion of Nubian does ovulating due to the male effect, indicate that female goats of this breed, maintained under tropical photoperiod, are more responsive than Alpine does to non-photoperiodic external stimuli, such as the presence of sexual active males.