Exigncias de lisina digestvel para juvenis de tilpia-do-nilo

ABSTRACT - This trial was carried out to determine the digestible lysine requirements of Nile tilapia juveniles. Ninety-six reverted fishes averaging initial weight of 5.72 ± 0.10 g were fed four diets (29.51% of crude protein and 3,235 kcal/kgof digestible energy) containing increasing levels of L-lysine HCl (0.1, 0.3, 0.5, and 0.7%), during 42 days. The followingtreatments were evaluated: dietary lysine levels of 1.04; 1.27; 1.51 and 1.741%. Fishes were allotted to 1000-L 16 tanks,as a completely randomized design with four treatments, three replicates and eight fishes per experimental unit. No treatmenteffects on hepatosomatic index, visceral fat, survival rate and water ether extract in the carcass were observed. The LinearResponse Plateau analysis of weight gain and feed:gain ratio versus digestible lysine level yielded an estimated digestible lysinerequirement of 1.56 and 1.44% for Nile tilapia juveniles, respectively. Quadratic effect of treatments on carcass yield thatincreased up to 1.61% of digestible lysine was observed. Considering the performance, it is recommended diets containing upto 1.44% of digestible lysine (5.23% of protein) for Nile tilapia juveniles.Key Words: lysine,