Assessment of S-metolachlor-Induced Biochemical and Histopathological Alterations in Cardiomuscular Systems of Domestic Chicks (Gallus gallus domesticus): A Toxicological Perspective.

S-metolachlor is a widely used chloroacetanilide herbicide in farming that functions by blocking fatty acid synthesis in weeds. Extensive use of S-metolachlor in agriculture has raised concerns regarding its toxicity in nontarget animals especially avian species; however, its potential toxicity effects on misri chicks Gallus gallus domesticus remain poorly understood. This study aims to investigate the cardiotoxic and myotoxic potential of S-metolachlor in adult Misri chicks. Ninety-six chicks were housed under standard environmental conditions for the period of 14 days following a 2-day acclimatization. Birds were randomly divided into six groups (n = 16) including one control group and five experimental groups that were administered to different doses of S-metolachlor 20, 40, 60, 80, and 100 mg/kg mass, respectively. Various antioxidant, biochemical, and histopathological biomarkers were assessed in serum and visceral organs. In the current experimental trial, the values of body weight and relative organ weight (p < 0.05) values decreased, while serum creatine kinase-MB, creatine phosphokinase, and lactate dehydrogenase significantly increased (p < 0.05) in high-dose groups indicating myocardial and skeletal muscles damage. Results indicated significantly decreased (p < 0.05) values of superoxide dismutase (SOD) only in heart, indicating a selective depletion of cardiac antioxidant capacity, rather than direct oxidative stress, although catalase (CAT), malondialdehyde (MDA), and glutathione peroxidase (GPx) showed no significant changes as compared to control group. Herbicide-treated groups showed histopathological changes including edema, progressive degeneration, myofibrillar changes, and inflammatory cell infiltration both in heart and muscle tissues in dose-dependent manner. The current study showed that S-metolachlor induces cardiotoxicity and myotoxicity in adult misri chicks and highlight the need for further molecular studies to elucidate the mechanisms of toxicity.