Dietary branched-chain amino acid valine, isoleucine and leucine requirements of fingerling Indian major carp, Cirrhinus mrigala (Hamilton)

Abstract

Three 8-week growth experiments were conducted to quantify the requirements of the fingerling Cirrhinus mrigala for the dietary branched-chain amino acids valine (experiment 1), isoleucine (experiment 2) and leucine (experiment 3). Six isonitrogenous (400/g) and isoenergetic (17·90k/) test diets were formulated with a gradation of 2·5/g for each test amino acid, valine (7·5–20/g), isoleucine (5·0–17·5/g) and leucine (7·5–20/g), and fed to randomly stocked fish in circular troughs. In experiment 1, the maximum weight gain (312%), best feed conversion ratio (FCR; 1·45) and best protein efficiency ratio (PER; 1·72) were obtained in fish fed 15·0g dietary valin/g. In experiment 2, the highest weight gain (317%), best FCR (1·47) and best PER (1·70) were recorded at 12·5g dietary isoleucin/g, and in experiment 3, the highest weight gain (308%), best FCR (1·46) and best PER (1·71) were noted at 15·0g dietary leucin/g. A quadratic regression analysis of weight gain, FCR and PER data showed an optimum requirement at 15·9, 15·0 and 14·8/g for valine, 13·2, 12·3 and 12·1/g for isoleucine and 15·6, 15·4 and 15·1/g for leucine in dry diets. Low body moisture and higher protein were noted in fish fed diets containing 15·5, 12·5 and 15·0g valine, isoleucine and leucine per kg, respectively. Body fat increased with increasing levels of the branched-chain amino acids. On the basis of a regression analysis of growth data, it is recommended that a diet for C. mrigala should contain valine at 15·2, isoleucine at 12·6 and leucine at 15·4/g dry diet, corresponding to 38·0, 31·5 and 38·5/g dietary protein, respectively.