The effect of ACTH on the GnRH-induced release of LH and testosterone in male white-tailed deer.

In order to investigate the possible link between stress and the impairment of the reproductive system, 12 yearling white-tailed bucks, born to mothers captured wild in southern Texas, were immobilized every 6 weeks over the period of 1 year. In half of experiments deer were injected i.m. with 20 i.u. of ACTH; in the second half, we used saline only. Simultaneously, in each experiment we also injected all deer i.m. with 100 micrograms of GnRH. Three blood samples were taken before and seven after treatment and plasma levels of cortisol, LH and testosterone (T) were later measured by RIA. Half of our yearlings were born to mothers which were fed high-protein-high-energy (HP-HE) diet during their pregnancy; the other half ws fed high-protein-low-energy diet (HP-LE). ACTH increased cortisol levels in both nutritional regimes. Cortisol levels in controls decreased with time but a more pronounced reduction was observed in HP-HE bucks as compared to HP-LE deer. GnRH significantly increased LH and T levels. However, only in summer, LH levels were higher in HP-LE fed deer than those fed HP-HE; in other seasons they were equal. Conversely, only in winter T levels were elevated in HP-HE fed deer as compared with HP-LE deer. We concluded that the pronounced suppression of reproductive hormones by ACTH or cortisol reported previously in domestic ungulates does not occur in white-tailed deer yearlings. Conversely, the low level of energy provided in food to mothers during their pregnancies significantly reduced peak levels of testosterone in their male offspring. This study further proved that white-tailed deer is a highly adaptable cervid species resistant to environmental stress.