摘要Objective: To determine the effects of a glyphosate-based herbicide on the oestrous cycle of rats.Methods: Fifteen adult Wistar rats were randomly divided into three groups. Group A served as the control group, while groups B and C received 250 and 500 mg/kg of glyphosate-based herbicide orally for five oestrous cycles, respectively. Stages of oestrous cycle, oestrous cycle index, length of cycle, oestrous cycle ratio, serum estradiol and progesterone levels were determined. Results: The proestrus and oestrus stages of the glyphosate-based herbicide groups increased significantly (P<0.05), although proestrus in group C was not significantly different from the control group. There was a significant decrease in the metestrus and diestrus of the glyphosate-based herbicide groups (P<0.05). The oestrous cycle index of the glyphosate-based herbicide treated groups was altered; this was characterized by an increase in the oestrous index and a decrease in the metestrus and diestrus indexes. The proestrus index of group B increased, while that of group C decreased. The length of the cycle of the glyphosate-based herbicide groups significantly decreased from the 1st and 3rd week till the end of the study in groups B and C, respectively (P<0.05). There was a significant increase in the oestrous cycle ratio of the glyphosate-based herbicide groups compared to the control group (P<0.05). Though the estradiol and progesterone levels of the glyphosate-based herbicide groups increased and decreased, respectively, they were not significantly different from the control group. Conclusions: Glyphosate-based herbicide at the doses of 250 and 500 mg/kg can alter the pattern of the oestrous cycle in rats.