Effects of dietary silymarin (SM) supplementation on growth performance, digestive enzyme activities, antioxidant capacity and lipid metabolism gene expression in large yellow croaker (Larimichthys crocea) larvae

A 30-day feeding trial was conducted to investigate the effects of dietary silymarin (SM) on growth performance, digestive enzyme activities, antioxidant capacity and lipid metabolism in large yellow croaker larvae (initial weight: 4.71 +/- 0.21 mg). Four iso-nitrogenous and iso-lipidic diets were formulated with 0, 50, 150 and 450 mg/kg of SM, respectively. Results showed that larvae-fed diets with 50 and 150 mg/kg SM had higher specific growth rate and weight gain rate than the control group (p < .05). Activities of trypsin in larval intestinal segments and lipase in larval pancreatic segments were significantly increased in larvae-fed diet with 50 mg/kg SM compared to the control group (p < .05). Total antioxidant capacity in larvae-fed diet with 50 mg/kg SM was higher than the control group (p < .05). Meanwhile, malondialdehyde contents were lower in larvae-fed diets with 50 and 150 mg/kg SM than the control group (p < .05). The triglyceride content in visceral mass was lower in larvae-fed diets with 50 and 150 mg/kg than the control group (p < .05). Results of gene expression revealed that dietary SM reduced visceral mass lipid accumulation probably through inhibiting lipid synthesis-related genes (srebp-1andfas) and promoting lipid oxidation-related genes (ppar alpha and cpt-1)at the transcriptional level. In summary, results of the present study indicated that the supplementation of 50 mg/kg SM could improve growth performance, digestive enzyme activities and antioxidant capacity, and reduce visceral mass lipid accumulation in large yellow croaker larvae.