Effects of dietary l-carnitine, plant proteins and lipid levels on growth performance, body composition, blood traits and muscular carnitine status in juvenile silver perch (Bidyanus bidyanus)

This study was carried out to understand the possible effects of supplemental dietary l-carnitine on the growth, body composition, blood traits and carnitine status in silver perch. A 2 × 2 × 2 factorial design was utilized to formulate the experimental diets, which contained plant protein sources to replace 0 or 70% of fish meal protein with 10 or 18% dietary lipid were supplemented with or without l-carnitine at 400 mg kg− 1. The juvenile fish (mean weight: 9.67 ± 1.04 g) were fed one of these isonitrogenous and isocaloric diets in triplicate for 10 weeks. Results showed that supplemental dietary l-carnitine significantly enhanced growth performance and feed utilization, meanwhile the addition of l-carnitine to the diet that was low in fishmeal and low in fat resulted in a lowering of ammonia excretion and a higher feed efficiency. The dietary lipid level significantly influenced the hepatosomatic index, viscerosomatic index and intraperitoneal fat ratio, while the intraperitoneal fat ratio of silver perch was noticeably reduced by the addition of l-carnitine in diets. The total plasma lipid, triacylglycerols and cholesterol values of the fish were altered by the dietary protein source or the dietary lipid level, but the effect of l-carnitine supplementation on the blood traits was unclear. Lipid contents of whole body and dorsal muscle were increased in the fish fed diets with the higher lipid level, whereas supplemented dietary l-carnitine significantly reduced the lipid contents of the whole fish. The concentrations of free carnitine and acid soluble carnitine in the muscle were higher in the silver perch that received diets supplemented with l-carnitine. The observations of this study revealed positive effects of l-carnitine supplemented in diets on growth enhancement, increases in muscular carnitine status, reduction of intraperitoneal fat ratio and the whole-body lipid contents in silver perch.

► This study was aimed at the effects of adding dietary L-carnitine on silver perch.
► Added dietary L-carnitine notably enhanced growth and feed utilization of the fish.
► The low-fishmeal, low-fat diet with L-carnitine led to less ammonia excretion.
► L-carnitine added diets reduced intraperitoneal fat ratio and body lipid contents.