Protein: energy ratio in practical diets for Nile tilapia Oreochromis niloticus

The present study was conducted to evaluate the interaction of protein and energy ratio in low protein (20, 25 and 30 %) diets for juvenile Nile tilapia (Oreochromis niloticus) (initial weight 7.44 ± 0.03 g). Dietary protein to energy (P/E) ratio of nine practical diets ranged from 66.84 to 115.14 mg protein/kcal energy. Each diet was randomly assigned to four replicate groups of fifteen fish. After 10 weeks, Fish fed the lowest dietary protein (20 %) and lowest energy (2,600 kcal/kg) diets were significantly smaller than fish maintained on D5 (25/2800) and D6 (30/2800), However, there were no significant differences among all the treatments except D1. The whole body moisture and protein levels were significantly influenced by dietary protein and energy content. Whole body energy content and digestible energy retention were significantly influenced by energy content of the diet. Conversely, dietary protein level significantly influenced protein retention but it did not influence digestible energy retention. Under the reported conditions, the response of tilapia to dietary energy or protein was seen only at the lower levels of inclusion and tilapia demonstrated limited protein sparing as dietary energy was increased. However, this did modify the carcass composition through higher dietary energy.