Tailoring a Diet for Nile Tilapia (Oreochromis niloticus) Culture in Northwest Mexico

This study evaluated the modification of a diet for Nile tilapia culture using plant protein sources locally available in northwest Mexico to limit the use of fish meal (FM), and the in vivo and in vitro apparent digestibility coefficients (ADC) of nutrients in the experimental diets using a closed recirculating system. Each diet (30% crude protein-CP) was assigned to five replicate tanks to evaluate the effects on biological performance of tilapia; three additional tanks per treatment were assigned for the evaluation of in vivo ADC of CP, lipid, carbohydrate and dry matter, and three more for the evaluation of in vitro ADC of CP. Tilapia fed the diets with 11%-FM and 22%-FM showed significantly higher (P < 0.05) final growth. In vivo ADC of CP was significantly higher for the 22%-FM (92.35%) and 11%-FM (92.31%) diets compared to the 0%-FM (85.36%); these data compared closely to in vitro ADC of CP (day 24: 93.46%, 89.63% and 86.92%, respectively), but a low correlation (r ² = 0.67) was observed. Results showed that it is possible to reduce FM inclusion in diets for Nile tilapia and improve growth performance using a plant protein mixture (soybean meal, alfalfa meal and corn gluten meal) of local ingredients.