Influence of graded level of dietary protein with equated level of limiting amino acids on growth, feed utilization, body indices and nutritive profle of snubnose pompano, Trachinotus blochii (Lacepede, 1801) reared in low saline water

Abstract

An experiment was conducted to delineate the effect of varying level of dietary protein with balanced level of limiting amino acids such as lysine and methionine on growth, feed utilization, body indices and digestive enzymology of snubnose pompano, Trachinotus blochii reared in low saline water. There were four experimental diets formulated with 350 (CP350), 400 (CP400), 450 (CP450) and 500 g/kg (CP500) crude protein and each with 100 g/kg crude fat and were assigned to four treatments, CP350, CP400, CP450 and CP500 respectively. Totally eighty four fingerlings with the body weight in the range of 16−18 g were randomly distributed in four treatment groups with each of three replicates. Fish were fed to apparent satiation twice daily with the assigned experimental diet. At the end of 13 weeks of feeding trial, weight gain percentage (WG%) and specific growth rate (SGR) of fish fed with CP400 and CP450 diets were significantly higher than those of fish fed with CP350 and CP500 diets. Growth rate on metabolic body weight (GRMBW), daily growth coefficient (DGC) and average daily growth (ADG) were higher in CP400 group and lower in CP350 group. The viscerosomatic index (VSI), hepatosomatic index (HSI), gastrosomatic index (GSI) and intra-peritoneal fat ratio (IPFR) showed an increasing trend as the crude protein content of the experimental diet increases and the maximum value was witnessed in CP500 treatment. Crude lipid and protein content of whole body tissue was found highest in CP400 and lowest level was noticed in CP350 group. The maximum intestinal protease activity was noticed in CP400 group. In conclusion, analysis of second degree polynomial regression revealed that the optimum dietary protein level could be in the range of 395.3–426.7 g/kg for maximum growth of juvenile snubnose pompano.