Exposure to a recently mated male increases ram sexual performance

Abstract

Previous studies reported that male sheep sexual performance does not improve following the observation of heterosexual behavior, which is in contrast to male cattle, goats, pigs and horses. The purpose of this study was to investigate the possibility that exposure to a recently mated ram may enhance ram sexual performance. Eight sexually experienced rams (1 year of age) were assigned to either mated ram stimulus (MRS) or non-mated ram stimulus (NMRS) conditions in a switchback design. The rams in the MRS condition were briefly (10 min) exposed to a penmate who had mated an ewe immediately beforehand. The males in the NMRS condition were exposed to a penmate who had been placed in an empty pen. The rams were allowed to freely investigate their respective stimulus penmate and then each male was placed with an estrous ewe for 15 min. The frequencies of anogenital sniffs, leg kicks, flehmen lip curls, mount attempts, mounts and ejaculations were recorded. Ejaculatory latencies were also recorded. Mean courtship (anogenital sniffs and leg kicks) and mounting (mount attempts and mounts) behavior frequencies were higher for the MRS condition ( P = 0.010 for both). Similarly, the individual mean frequencies of anogenital sniffs, leg kicks, mount attempts and mounts were higher when males interacted with a ram which had just mated ( P = 0.046; 0.016; 0.048; 0.029, respectively). Mean flehmen lip curl and ejaculation frequencies were not different between the two conditions ( P = 0.900 and 0.700). These data suggest that an odor cue associated with the ewe or mating, perse, was emitted by the penmate which was allowed to mate. This cue then enhanced the sexual performance of rams in the MRS condition.