Protein requirement of juvenile striped catfish, Pangasianodon hypophthalmus

A trial was conducted to determine the dietary protein requirement for growth of juvenile striped catfish (Pangasianodon hypophthalmus). Iso-energetic semi-purified diets (similar to 19.78 MJ kg(-1)) with six levels of protein 20% (T-1), 25% (T-2), 30% (T-3), 35% (T-4), 40% (T-5), and 45% (T-6) were fed to triplicate groups of fish (initial mean weight 4.27 to 4.57 g) to satiation twice daily for 60 days. Growth, feed conversion, protein utilization, intestinal digestive enzyme activities, and body composition were measured as response variables. Best growth (P < 0.05) was observed in fish fed with 40% dietary protein, and second order polynomial regression analysis (y = - 0.0011x2 + 0.0816x + 0.0642; R-2 = 0.9241; dietary protein levels as independent variable and specific growth rate as dependent variable) gave a protein requirement for growth of 37.1%. A minimum feed conversion ratio (FCR = 1.38) was found in fish fed with 35% dietary protein. Apparent net protein utilization (ANPU) was found to decrease (from 39.57 to 16.15%), with increasing dietary protein levels (P < 0.05). Protease and amylase activities were found to be in opposition to each other, with increasing dietary protein levels. The highest protease (0.59 mu mol of tyrosine released min(-1) mg(-1) protein) and lowest amylase activities (7.99 mu mol of maltose released min(-1) mg(-1) protein) were observed in fish fed with 40% dietary protein (P < 0.05); whereas lipase activity (P > 0.05) was found to be independent of dietary protein levels. Whole body carcass composition (except ether extract) varied with the dietary protein level, and significant higher values of moisture content (72.31%), crude protein (18.83%), and ash content (4.33%) were observed in the treatment group fed with 40% dietary protein. Hence, it may be concluded that the dietary protein requirement for growth of P. hypophthalmus juveniles is 37.1%.