Abstract Introduction: Cadmium, as an environmental pollutant, can exert oxidative stress on spermatogenesis and sperm morphology. This study was performed to investigate not only the effect of cadmium on viability, motility and acrosome integrity of ram sperm but also examine the protective role of silymarin, as an antioxidant, on cadmium toxicity. Epidydimal sperm obtained from Farahaniˊs ram divided into four groups: 1. sperm at 0 hour 2. Sperm incubated for180 minutes (control) 3. sperm treated with cadmium chloride for 180 minutes and 4. sperm treatment with silymarin+cadmiumchloride for 180 minutes. MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide) method was used to assess sperm viability. Sperm motility was done according to World Health Organization guidelines while acrosome integrity in the sperm was evaluated by comassie brilliant blue staining. Data were analyzed using one way ANOVA followed with Tukeyˊs test. The percentage of sperm viability, motility and acrosome integrity was significantly decreased in cadmium chloride-treated group compared to the control. In silymarin+cadmiumchloride group, silymarin could compensate the adverse effect of cadmium chloride on sperm parameters (except sperm motility) compared to cadmium chloride group. Silymarin as a potent antioxidant prevented adverse effect of cadmium on some ram sperm parameters.
