The effect of dietary silymarin (Silybum marianum) at graded inclusion levels on production performance, gut morphology and hepatic antioxidant status in broilers not subjected to pathogen challenge.
Abstract
This study investigated the effects of graded levels of dietary silymarin (SM) supplementation at 0, 2, 4, 6, 8, 10 and 12 [g/kg] diet on growth performance, energy and nutrient availability, intestinal morphology, mucous cell populations and hepatic antioxidant status in unchallenged broiler chickens. Growth performance variables, including daily feed intake, weight gain and mortality‑corrected feed conversion ratio, were not influenced (p > 0.05) by SM inclusion. Although N-corrected apparent metabolisable energy, dry matter and nitrogen retention coefficients differed among treatments (p < 0.001), these effects were inconsistent and displayed no dose-dependent pattern (p > 0.05). No changes in breast meat colour were observed (p > 0.05). Jejunal villus morphometry and mucous cell types were largely unaffected by dietary treatments. Villus height and width did not vary among diets (p > 0.05), and although crypt depth, mucosal thickness and mucous cell subtype counts showed some treatment-specific differences (p < 0.001), none followed a consistent dose-response dependent trend. All measured values fell within expected physiological ranges for broilers at this age, indicating that SM exerted no substantive impact on intestinal structure or mucosal secretory function. Similarly, hepatic responses to SM were minimal, as the relative liver weight did not differ among treatments (p > 0.05). Compared to the control, hepatic coenzyme Q10 concentration increased in 12 [g/kg] SM (p < 0.05). However, the rest of the hepatic antioxidants showed limited or no sensitivity to SM supplementation, and no clear dose-related effects were detected (p > 0.05). Overall, SM supplementation significantly affected some variables related to gut physiology, hepatic antioxidant status and energy and nutrient availability, although these effects were not consistently related to dietary SM inclusion level.