Evaluation of commercial feeds intended for the Brazilian production of Nile tilapia (Oreochromis niloticusL.): nutritional and environmental implications

This study evaluates the composition and nutritional content of feeds for the commercial production of Nile tilapia (Oreochromis niloticus L.) in Brazil. The feeds were assessed from a nutritional standpoint and as potential polluting agents of aquatic environments. The nutritional contents of each feed were calculated by considering the nutritional contributions of its ingredients based on reference tables. These contents were compared to the nutritional recommendations for O. niloticus. Altogether, 130 feeds were analysed, including 32 meant for fingerlings, 30 meant for juveniles, 38 meant for the growth stage and 30 meant for the termination stage. The overall digestibility of the feeds in terms of dry matter utilization was estimated to be 68.5%. Phosphorus was the nutrient with the lowest mean digestibility (51.2%), while protein had the highest mean digestibility (86.6%). Calcium and phosphorus levels exceeded their recommended values by 256.2% and 31.3%, respectively. The ratios of methionine, methionine plus cysteine, threonine and tryptophan to lysine were below their recommended values. The indigestible contents of nitrogen and phosphorus were 6.96 (±2.57) and 7.35 (±1.77) g kg−1, respectively. The information obtained here provides a reference for estimating the productive and polluting potential of feeds used in the production of Nile tilapia.