The effect of decreasingdietary crude protein (CP) with supplementation of amino acids, based on theideal protein concept on Nile tilapia (Oreochromis niloticus) fingerlingsperformance was evaluated. A total of 396 fingerlings from Thai strain, with0.80 ± 0.17 g of BW, was allotted to a randomized block design, withsix levels of CP (32, 31, 30, 29, 28 and 27% of CP) in the diets, six replicationswith 11 fish each. The diets were formulated to be isocaloric and digestibleisolysine, remaining constant the amino acids to lysine minimum ratio. The fishwere kept in 36 aquariums of 130 L, equipped with water supply, controlled temperatureand individual aeration, and ad libitum fed six times a day for 40 days. Thereduction of CP content of the diet did not affect weight gain, specific growthrate, feed intake, digestible lysine intake, body protein content, fat and proteindeposition rates and nitrogen retention efficiency of fishes. The fish fed dietswith 27% of CP lower feed: gain ratio, lysine efficiency for gain, nitrogenintake and body water and higher protein efficiency for gain and body fat content.The level of crude protein of the diet for Nile tilapia fingerlings can be reducedby four percentage points (from 32 to 28%), without negative effect on the performanceof the animals, since the diets are supplemented with essential limiting aminoacids.
