Suplementa？？o de metionina e/ou lisina em ra？？es para juvenis de tambaqui (Colossoma macropomum Cuvier, 1818)

it was evaluated the effect of the reduction of crude protein level (cp) and the lysine and/or methionine supplementation in total ammonia nitrogen excretion on tambaqui (colossoma macropomum) juveniles. the experiment developed in a factorial and randomized design with two levels of protein contents (20% and 25% cp) and four levels of amino acid supplementation: a) dl-methionine (0% of cp) and l-lysine (0% of cp), b) dl-methionine (3% of cp), c) l-lysine (5% of cp), d) dl-methionine (3% of cp) + l-lysine (5% of cp), during 55 days. the water sampling from experimental units was done at 3 moments (10 day, 270 day e 550 day). in these days, 3 samples of each experimental unit were collected in elapsing of the time (08:00 a.m., 02:00 p.m. and 08:00 p.m.). the ammonia excretion data were analysed by repeated-measures anova (p>0,05) with time as within effect. the reduction of 5% in diet protein, decreased in 28,4% total ammonia excretion decreased, however, the lysine and methionine supplementation did not influenced this factor.