The Effect of Silymarin on Antioxidant, Performance, Immunoglobulin Protein Levels, Cecal Microbiota, and Hemobiochemical Indicators in Heat Stressd Broilers

This study examined the effects of dietary inclusion of silymarin on performance, and physiological responses of broilers exposed to heat stress (HS) conditions. A flavonoid complex known as silymarin is extracted from the Silybum marianum plant, which is renowned for its medicinal properties. A total of 500 one-day-old male broiler chickens (Ross 308) were divided into five dietary treatment groups with five replicates each. Thermoneutral (TN), heat stress (HS), and HS with a diet supplemented with four different silymarin at rates of zero, 150, 300, and 450 mg/kg, respectively (S0, S1, S2, and S3 groups). Broiler chickens were reared under normal conditions until d 25 and after that the heat stress (34 ± 2◦C) was applied for eight hours (0900 to 1700 h) from d 25 to 42. Exposure to HS significantly reduced feed intake, weight gain, antioxidant capacity, hematocrit (HCT), hemoglobin (HGB), and Lymphocytes (LYM) in and elevated feed conversion ratio (FCR), mortality, serum malondialdehyde, and heterophils (HET) compared to the TN group. Moreover, HS decreased the immunoglobulin G (IgG), immunoglobulin M (IgM), and caecal lactic acid bacteria population (CLBP), but increased caecal coliform population (CCFP), and total cholesterol (TC), triglyceride (TG), aspartate transaminase (AST), alanine transaminase (ALT) levels in serum (P < 0.01). Among the HS groups, supplementary silymarin improved growth performance indices and reduced mortality (P < 0.01). The HET and HET to LYM ratio was reduced by silymarin supplementation. The HS-induced effects on of TG, TC, ALT, and AST concentration in serum were alleviated by dietary silymarin supplementation (P < 0. 01). Moreover, the HCT, HGB, glutathione peroxidase, superoxide dismutase, IgM, and IgG level were increased. Silymarin inclusion reduced malondialdehyde in serum (P < 0.01). In addition, CLBP increased, and CCFP decreased by silymarin inclusion. In conclusion, silymarin inclusion may be used to alleviate the physiological responses of broilers exposed to heat stress.