Background and Aim: Salinomycin sodium, a licensed coccidiostat in rabbits, is used for fattening at a dose of 20–25 mg/kg. Salinomycin toxicity may arise from many risk factors (e.g., overdosage or use in non-target animal species). Silymarin extracted from milk thistle has antioxidant, anti-inflammatory, and antiviral properties. This study aimed to investigate the adverse impacts of oral administration of salinomycin for 28 consecutive days and how to reduce its risks and side effects by administering silymarin.

Materials and Methods: Eighty-four male New Zealand White bucks (1.750–2.000 kg) were randomly divided into seven groups (12 each). Group one was the control. Groups two and three were administered salinomycin orally (doses of 20 and 40 mg/kg ration). Group four was administered salinomycin (20 mg/kg ration) and silymarin (6.5 mg/kg body weight [BW]). Group five received salinomycin (40 mg/kg ration) and silymarin (13 mg/kg BW). Groups six and seven were administered silymarin at doses of 6.5 and 13 mg/kg BW. Rabbits were euthanized and slaughtered on day 29 using the Halal method. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine, urea, total proteins, albumin, total cholesterol, and high- and low-density lipoprotein (HDL and LDL) were analyzed in serum. Glutathione (GSH), superoxide dismutase (SOD), catalase, and malondialdehyde (MDA) were estimated in the liver. A histopathological investigation was performed on the liver and kidney.

Results: The MDA activity, AST, ALT, total protein, albumin, total cholesterol, triglyceride, LDL, urea, and creatinine values were significantly elevated in groups two and three. The GSH, catalase, SOD, and HDL were significantly lower in these groups than in the control group. There were moderate pathologic changes in the liver and kidney of the third group . However, the results of the fourth and fifth groups improved more than those of the second and third groups. The results of the sixth and seventh groups were nearly the same as those of the control group.

Conclusion: Salinomycin toxicity was caused by oxidative damage because of reactive oxygen species formation. Silymarin (6.5 or 13 mg/kg BW) tends to prevent and treat accidental toxicity. However, the high dose of silymarin (13 mg/kg BW) had more renal and hepatoprotective capacities.

Keywords: anticoccidial drugs, feed additives, liver enzymes, oxidative biomarkers, rabbits, salinomycin, silymarin.