Abstract
Light is an important environmental factor that controls the regulation of physiological functions of organisms. Melatonin is considered as one of the major hormones that play an important role in protecting body from many harmful effects and acts as a powerful anti-oxidant source to controlling the levels of antioxidant enzymes within the body. The main objectives of this work were to study the effect of 1) photoperiod changes and 2) exogenous melatonin hormone treatment on the sperm properties, body and testis weight, embryo characteristics, and concentration level of melatonin and testosterone in treated rat serum. This study has been conducted using thirty-six male rats and one hundred and twenty female rats. Animals were divided into six groups, each group containing six males and twenty female rats. Our results showed a significant influence of photoperiod changes on the melatonin and testosterone hormones concentration in rats' serum, body weight only, while the other characteristics not affected. As for the effect of melatonin it has been found that the movement of sperm in GIII and IV, as well as embryos absorbed and newborns weight traits has been significantly affected, while the rest of the properties were not significantly affected by melatonin treatment.