Effects of dietary fish oil replacement by soybean oil and L-carnitine supplementation on growth performance, fatty acid composition, lipid metabolism and liver health of juvenile largemouth bass, Micropterus salmoides

This study was conducted to investigate the effects of dietary fish oil replacement by soybean oil and L-carnitine supplementation on growth performance, fatty acid composition, plasma biochemical parameters, lipid metabolism, hepatic antioxidant ability and morphology of juvenile largemouth bass, Micropterus salmoides. Five isonitrogenous and isoenergetic experimental diets were formulated by replacing 0 (Diet 1), 50% (Diet 2) and 100% (Diet 3) of fish oil by soybean oil, and 50% (Diet 4) and 100% (Diet 5) of fish oil by soybean oil supplemented with 0.02% L-carnitine. After 8 weeks of growth trial, dietary fish oil replacement by soybean oil and L-carnitine supplementation significantly increased final body weight and weight gain rate except for fish fed Diet 3 (P < 0.05). No significant effects were observed in the composition of back muscle and liver among all groups (P > 0.05). Dietary fish oil replacement by soybean oil not only caused oxidative stress and liver damage, but also decreased the content of long-chain polyunsaturated fatty acid such as ARA, EPA and DHA in muscle and liver of fish. However, dietary L-carnitine supplementation could improve growth performance, lipid metabolism and liver health of fish. In conclusion, 50% of fish oil can be replaced by soybean oil with no adverse effects on growth performance, plasma biochemical parameters and liver health, and dietary 0.02% L-carnitine supplementation was beneficial to the health of fish fed dietary fish oil replacement by soybean oil.