Dietary supplementation with l-carnitine for Nile tilapia juveniles

This study evaluated the influence of dietary supplementation with l-carnitine on growth performance, gut and muscle histological parameters, blood hematology and plasma biochemical parameters, and the activity of antioxidant enzymes in the liver of Nile tilapia juveniles. Three inclusion levels of l-carnitine were evaluated (500; 1000; and 2000 mg kg−1 of diet), in addition to a basal diet. Groups of 12 fish were randomly assigned in 12 experimental units, and fed four times a day until apparent satiety, for 100 days. The fish fed diets containing either 500 or 1000 mg kg−1 of l-carnitine presented higher weight gain, specific growth rate, and filet yield, while the inclusion of 1000 mg kg−1 of l-carnitine reduced the lipid content of the filet. Regardless of the level of inclusion of l-carnitine, there was an increase in the enzyme catalase in the liver. With increasing levels of l-carnitine in the diets, reductions of the gut fold size and tunic thickness were also observed, while the growth of muscle fibers was not influenced by supplementation. The highest inclusion level (2000 mg kg−1) has negatively influenced weight gain, fat deposition and triacylglycerol. It was concluded that the inclusion of the l-carnitine in the diets resulted in higher activity of the enzyme catalase, while a 1000 mg kg−1 dietary supplementation with l-carnitine improves growth performance and reduces the lipid content of the filet of Nile tilapia. •The inclusion of 500, 1000 and 2000 mg kg−1 of l-carnitine was tested in diets for Nile tilapia.•Dietary inclusion of 500 and 1000 mg kg−1 of l-carnitine improves the growth of Nile tilapia.•The lipid content of the filets decreases in fish fed 1.000 mg kg−1 of l-carnitine.•The catalase activity in the liver increased in the fish fed with the diets l-carnitine.