Effect of Dietary Energy to Protein Ratio on Growth, Biological Indices, Proximate Composition, and Amino Acid Profiles in the Muscle of Varicorhinus macrolepis

A 150-d feeding experiment was conducted to assess the effect of the dietary energy to protein ratio (E/P ratio) on growth, biological indices, proximate composition, and amino acid profiles in the muscle of Varicorhinus macrolepis. Six experimental diets were formulated with different E/P ratios (30.51, 33.90, 37.82, 42.34, 47.70, and 54.09kJ/g). In the experiment, 360 fish with a mean weight of 8.75g (SD, 0.59) were randomly divided into six groups (three replicates per group, 20 fish per replicate) and fed three times daily with the experimental diet. Results showed that when the dietary E/P ratio was 37.82kJ/g, Varicorhinus macrolepis tended to gain the highest specific growth rate. With a change in the increment of dietary E/P ratio, the condition factor, intestosomatic index, hepatosomatic index, and viscerosomatic index all changed in the quadric polynomial regression model. Muscle crude lipid content showed a tendency of leveling-off first and then increased with increasing dietary E/P ratio. Varicorhinus macrolepis gained the highest concentration of total amino acids and essential amino acids when the dietary E/P ratio was 37.82kJ/g. Except for methionine+cysteine, phenylalanine+tyrosine, and the amino acid score of lysine, the amino acid scores and chemical scores of the other essential amino acids were highest when the dietary E/P ratio was 37.82kJ/g. These results suggest that Varicorhinus macrolepis obtained optimal growth and muscle amino acid composition when the dietary E/P ratio was 37.82kJ/g.