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

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/kg) and isoenergetic (17.90 kJ/g) test diets were formulated with a gradation of 2.5 g/kg for each test amino acid, valine (7.5-20 g/kg), isoleucine (5.0-17.5 g/kg) and leucine (7.5-20 g/kg), 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 15.0 g dietary valine/kg. In experiment 2, the highest weight gain (317 %), best FCR (1.47) and best PER (1.70) were recorded at 12.5 g dietary isoleucine/kg, and in experiment 3, the highest weight gain (308 %), best FCR (1.46) and best PER (1.71) were noted at 15.0 g dietary leucine/kg. A quadratic regression analysis of weight gain, FCR and PER data showed an optimum requirement at 15.9, 15.0 and 14.8 g/kg for valine, 13.2, 12.3 and 12.1 g/kg for isoleucine and 15.6, 15.4 and 15.1 g/kg for leucine in dry diets. Low body moisture and higher protein were noted in fish fed diets containing 15.5, 12.5 and 15.0 g 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/kg dry diet, corresponding to 38.0, 31.5 and 38.5 g/kg dietary protein, respectively.