Aquaculture, 80 (1989) 121-133 121 Elsevier Science Publishers B.V.. Amsterdam - Printed in The Netherlands zyxwvutsrqponmlkjihgfed Effect of Dietary Protein Level and Amount of Plant Ingredient zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIH (Phaseolus aureus) incorporated into the Diets on Consumption, Growth Performance and Carcass Composition in Oreochromis niloticus (L.) Fry SENA S. DE SILVA and RASANTHI M. GUNASEKERA Departments of Fisheries Biology and Zoology, University of Ruhuna, Matara (Sri Lanka) (Accepted 13 October 1988) ABSTRACT De Silva, S.S. and Gunasekera, R.M., 1989. Effect of dietary protein level and amount of plant ingredient (Phaseolus aureus) incorporated into the diets on consumption, growth perform- ance and carcass composition in Oreochromis niloticus (L.) fry. Aquaculture, 80: 121-133. Feeding trials were conducted for a IO-week period on young 0. niloticus of mean weight 2.92 ? 0.3 g maintained on 15 isocalorific diets with protein contents of 20%, 25% and 30%, and with pro- gressively increasing substitution levels (13% to 50% ) of the legume green gram (Phaseolus au- reus: synonym Vigna radiata). Daily food consumption was variable. The mean consumption, expressed either as g/g fish day-’ or g/fish day-‘, did not vary significantly between plant-pro- tein-substituted diets at any one protein level, except in one instance. The overall consumption was independent of the dietary protein content at lower protein levels, and of the amount of plant ingredient in the diets. Growth (percent average daily gain in weight (%ADG) ), food conversion ratio (FCR) and protein efficiency ratio (PER) ranged between 3.13 (G,P,,) and 7.79 (CP,,), 3.21 (G50P20) and 1.53 (G,,P,,), and 1.51 (G5,,P2,,) and 2.99 (Gs7P2,,), respectively. In parentheses are the dietary codes where the subscript of P indicates the dietary protein level, that of G the level of incorpo- ration of the plant ingredient and C the control diets. The best %ADG and FCR were observed at the 25% level of plant-ingredient substitution at all three dietary protein levels. Carcass compo- sition indicated that protein deposition was higher with high-protein diets. INTRODUCTION zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA There is an increasing attempt to develop practical diets for fish in which a significant proportion of the fishmeal component is substituted by readily available plant products (Gropp et al., 1979; Jackson et al., 1982; Winfree and Stickney, 1984; Robinson et al., 1985; Wee and Wang, 1987), single-cell pro- teins (Matty and Smith, 1978; Beck et al., 1979; Appler, 1985) and with cheap 0 1989 Elsevier Science Publishers B.V.