Replacement of fish meal by plant proteins in the diet of Nile tilapia: digestibility and growth performance

Apparent digestibility coefficient (ADC) values for a number of ingredients of plant or animal origin were obtained in order to formulate diets based on such values and to evaluate growth performance of Nile tilapia Oreochrom is niloticus fed four experimental diets in which fish meal was gradually r eplaced by a mixture of other ingredients. The digestibility of various diet components was measured by using an inert marker in the feed and by using the Guelph faeces collecting system. ADC v alues of the ingredients tested were generally high, especially for fish me al. It was found that extruded pea seed meal (92.6%), defatted soybean meal (94.4%), full-fat toasted soybean (90.0%) and micronized wheat (88.6%) wer e the best vegetable proteins tested. Lupin seed meal and faba bean meal ha d similar ADC values for protein and energy. Groups of tilapia, initial mean body weight (SD) 6.7 (0.1) g, were fed expe rimental diets with the same digestible protein (DP) and digestible energy (DE) containing graded levels of a mixture of vegetable ingredients as part ial or total replacement of fish meal protein. A growth trial was conducted over 12 weeks as partial or total replacement of fish meal protein. A grow th trial was conducted over 12 weeks at a water temperature of 25 degrees C . Significant differences were observed for weight gain among tilapia fed d iets D0, D33, D66 and D100 (containing only animal protein, 33, 66, and 100 % of plant protein, respectively). No significant differences were observed for voluntary intake among tilapia fed diets D0, D33 and D66. These values were significantly lower than those observed for tilapia fed plant protein based diet (D100) and suggest the possibility of partial replacement of fi sh meal by vegetable proteins without negative effects.