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

Abstract

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 54.09 kJ/g). In the experiment, 360 fish with a mean weight of 8.75 g (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 37.82 kJ/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 37.82 kJ/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 37.82 kJ/g. These results suggest that Varicorhinus macrolepis obtained optimal growth and muscle amino acid composition when the dietary E/P ratio was 37.82 kJ/g.