Effects of glyphosate-based herbicide-contaminated diets on reproductive organ toxicity and hypothalamic-pituitary-ovarian axis hormones in weaned piglets

At present, glyphosate (GLP) is the most produced and used herbicide in the world. With the large-scale use of glyphosate-based herbicides (GBHs), their toxic effects on animals and plants have increasingly become a concern. Based on the Codex Alimentarius Commission (CODEX) dose (20 mg kg^-1) and the dose set by the government (40 mg kg^-1), four experimental groups in which Roundup® (R) herbicide was added to the feed of weaned piglets at GLP concentrations of 0, 10, 20, and 40 mg kg^-1 were designed. The results showed that R had no significant effect on the vulvar size or index of reproductive organs but that it could affect the tissue morphology and ultrastructure of the uterus and ovary. With the increase in GLP concentration, the activities of antioxidant enzymes [SOD (P < 0.05) and GPx (P = 0.002)] in the uterus showed significant increases. Compared with the control group, the content of hydrogen peroxide (H₂O₂) in the treatment groups increased significantly (P < 0.05), the malondialdehyde (MDA) content in the 10 mg kg^-1 treatment group was significantly higher than that in the control group. We measured hypothalamic-pituitary-ovarian axis (HPOA) hormones and also found that GLP significantly increased luteinizing hormone-releasing hormone (LHRH), gonadotropin-releasing hormone (GnRH) and testosterone (T) content (P < 0.05) and decreased follicle-stimulating hormone (FSH) content (P < 0.05). In summary, although R does not affect the vulvar size or reproductive organ index of weaned piglets, it changes the morphology and ultrastructure of the uterus and ovaries, interferes with the synthesis and secretion of HPOA hormones, and causes changes in the balance of the antioxidant system of uterus. This study provided a theoretical basis for preventing reproductive system harm caused by GBHs.