Prenatal androgen exposure induces perturbation of sexual behavior in ewes

For most mammals, an excessive prenatal exposure to testosterone is known to induce significant disturbances both in physiology and behavior. While the effect of prenatal exposure to testosterone has been studied in ewes, sexual behavior has been less studied. Here we investigate the perturbation of the sexual behavior of ewes induced by prenatal steroid exposure. In this study 43 pregnant ewes were injected with testosterone propionate during the second third of gestation, and 23 prenatally androgenized (PNA) females were compared to 22 control females. Physiology and behavior were monitored for 2.5 years. Puberty, analysed through progesterone secretion, occurred in the same way in both groups. However, by counting the estrous cycles over two breeding seasons, we observed that PNA ewes had fewer estrous cycles (18.41 vs 14.41; p < 0.01). Despite this observation, most of the hormones involved in reproductive functions were found in similar concentrations in both groups. Despite the lack of a major impact of prenatal testosterone injection on hormone levels, we observed major changes in the behavior of the androgenized females. PNA females were more aggressive in a context of food competition with an increased occurrence of beats and blocking behavior (p < 0.001). While observed in their home pen, all but one of the PNA ewes exhibited male-like sexual behavior compared with less than half the control ewes (p < 0.001). Basal plasma levels of glucose and insulin as well as insulin sensitivity did not differ between groups. All together, these results seem to show that androgenisation during the second third of gestation in sheep has an impact on sexual behavior without a major impact on circulating hormone levels.