Comparative Evaluation of Dietary Protein Source And Level on Growth Performance and Nutrient Retention In <i>Mugil cephalus</i> (Linn.) Fry

Abstract

Ten diets (1-10) with varying protein levels (35, 38, 40, 42 and 45%) were formulated using processed full fat soybean (diet 1-5) and fish meal (diets 6-10) as the major protein sources. Mugil cephalus fry (mean body weight 0.5±0.01 g) were maintained in glass aquaria in inland saline groundwater (15 %o) under laboratory conditions (LD 12:12 at 20±1°C) and fed twice daily for 70 days at 5% body weight on one of the ten experimental diets. Studies have revealed that growth performance (in terms of live weight gain, SGR and growth per cent gain), nutrient retention (PER, GPR and APD), accumulation of carcass protein and fat were significantly (p < 0.05) high in the groups fed on diet containing 40% protein, irrespective of source, however, the values were high for the diet containing processed full fat soybean as the protein source. Further, the fry fed on soybean containing diet (at 40%) had high feed conversion efficiency and apparent protein digestibility (82.7%) and also excreted significantly low (p < 0.05) ammonia (N-NH4) and reactive phosphate (0-PO4) in the holding water in comparison with the fry fed on fish meal containing diets. From these studies, thus, it is evident that supplementary diet with 40% protein and 9.1% fat, 18.5 k]/g gross energy and a P/E ratio of 109.0 mg/KCal of metabolized energy appears to be optimal for maximising the growth of M. ceplwlus when grown in inland saline groundwater.