Effect of Predator Stress on the Reproductive Performance of Female Mice after Nonsurgical Embryo Transfer.

Predator stress can exert detrimental effects on female mammals, leading to disrupted reproduction. Although many studies have addressed the effects of predator stress on reproductive output in rodents, few studies have focused on the effect of visual or auditory stress on pregnant females. In this study, we investigated the possible effect of predator stress, either visual only or combined visual and auditory (visual+auditory), on the reproductive performance of female mice after nonsurgical embryo transfer. Reproductive performance was assessed as pregnancy rate, implantation rate, gestation length, live pup rate, and neonatal birth weight. Moreover, serum cortisol and progesterone levels in dams were measured by using electrochemiluminescence immunoassay. Exposure to predator (cat) stress did not lead to a significant change in pregnancy rates in the tested mice. However, the stressed mice showed significantly decreased implantation rates compared with the control group. Similarly, the live pup rate and neonatal birth weight were significantly lower in the group exposed to predator stress than in the control group. Furthermore, mice exposed to visual+auditory stress showed a significant reduction in gestation length compared with the control mice. Our data showed that predator visual+auditory stress as combined stimuli significantly increased serum cortisol level. In contrast, progesterone levels did not significantly vary among the experimental groups. Taken together, our findings imply that predator stress adversely affects the reproductive efficiency of pregnant mice by decreasing the implantation rate, live birth rate, and neonatal birth weight and by prolonging gestation length.