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Keywords:

  • Cirrhinus mrigala;
  • dietary arginine requirement

Abstract

Dietary arginine requirement of fingerling Indian major carp, Cirrhinus mrigala (4.20 ± 0.05 cm; 0.60 ± 0.02 g) was determined by conducting a 8-week feeding trial with casein–gelatine-based diets (400 g kg−1 crude protein; 17.90 kJ g−1, gross energy), containing crystalline amino acids with graded levels of l-arginine (10, 12.5, 15, 17.5, 20 and 22.5 g kg−1, dry diet). Fish were randomly stocked, in triplicate groups, in 55-L indoor polyvinyl flow through circular tanks and fed experimental diets at 5% of their body weight divided into two feedings at 08.00 and 16.00 hours. Live weight gain (321%) and feed conversion ratio (FCR 1.40) were significantly (P < 0.05) higher in fish fed diet containing 17.5 g kg−1dietary arginine compared with other diets. Second-degree polynomial regression analysis of live weight gain, FCR and protein efficiency ratio data indicated requirements for dietary arginine at 18.7, 18.4 and 18.3 g kg−1 of the dry diet, respectively. Maximum carcass protein, and minimum moisture and fat contents were noticed at the requirement level. Carcass ash content remained insignificantly different among the treatments except at 17.5 g kg−1 dietary arginine showing significantly higher ash content. Based on the above results, it is recommended that the diet for fingerling C. mrigala should contain arginine at 18.4 g kg−1, dry diet, corresponding to 46 g kg−1 dietary protein for optimum growth and efficient feed utilization.