Optimization of dietary protein to energy ratio (P/E ratio) for Sutchi catfish, Pangasianodon hypophthalmus (Sauvage, 1878) fingerlings
Md. Zulfikar Ali, Mritunjoy Paul, Prasanta Jana, Md. Khalilur Rahman and Yahia Mahmud
A 60 days feeding trial was conducted to investigate the optimum dietary protein to energy ratio (P/E ratio) in Sutchi catfish Pangasianodon hypophthalmus. The same aged uniform size fingerlings of P. hypophthalmus were randomly distributed into groups of 40 fish (averaging 2.55 ± 0.05g in weight) per 70-L fiber glass tank in triplicates following completely randomized design. Six experimental diets were formulated to contain two levels of crude protein (25 and 30%) and three lipid levels (5, 10 and 15%) formed 25/5, 25/10, 25/15, 30/5, 30/10 and 30/15% P/E ratio contained 15.50, 17.36, 19.38, 16.52, 18.38 and 20.35 kJ g-1 gross energy. Feeding rate and frequency were 10-8% of their body weight 3-2 times daily. The highest (P<0.05) weight gain was observed for fish consuming that diet which contained 30/10% P/E ratio. The optimum dietary P/E ratio found for P. hypophthalmus fingerlings is 16.33 mg protein kJ-1 of GE, for a diet containing crude protein 30%, crude lipid 10% and gross energy 18.38 kJ g-1. Signiï¬cantly indifferent (P>0.05) values of protein utilization were found in-between the both (higher and lower) protein diets. Higher lipid deposition (P<0.05) in whole body and liver was observed with increasing dietary lipid level at each protein diet and as higher (P<0.05) for the lower protein diets. Significantly (P<0.05) lower liver glycogen level was found with increasing dietary lipid at each protein level. No significant (P>0.05) difference was found in digestive enzyme activities (amylase, protease and lipase) in ï¬sh fed with different experimental diets. Hence, it may be concluded that Sutchi catï¬sh P. hypophthalmusperformed best the diet containing 30%, 10%, 18.38 kJ g-1 and 16.33 mg protein kJ g-1 GE protein, lipid, gross energy, and P/E ratio, respectively.