PROTEÍNA BRUTA EM RAÇÕES PARA ALEVINOS DE TAMBAQUI E SUA REDUÇÃO COM SUPLEMENTAÇÃO DE AMINOÁCIDOS

Abstract

The current study was aimed at evaluate the effect of dietary crude protein reduction with amino acids supplementation, based on the concept of ideal protein in diets for fingerling tambaqui (Colossama macropomum), two experiments were carried the research sector of fish nutrition of Center of Agrarian Sciences and Environmental of Federal University of Maranhão. The fingerlings were kept in 30 polythene tanks with capacity volume of 500 litres in recirculation system. Diets were supplied in five meals a day with duration of 45 days. Performance parameters, carcass yield, corporal composition, the daily protein and fat deposition rates and nitrogen retention efficiency of the fishes were evaluated. The first experiment was aimed to determine the requirement of crude protein (CP) for tambaqui fingerlings diets. 750 fingerlings were used with initial weight 0.35 ± 0.09 g, distributed in completely randomized design with six treatments, five repetitions and twenty five fish per experimental unit. The treatments had consisted of in six isocaloric, isocalcic and isophosphoric experimental diets, with different levels of CP (20, 24, 28, 32, 36 and 40%). We re not observed effects of crude protein levels on feed intake and carcass yield. Crude e protein consumption increased linearly and the protein efficiency ratio decreased linearly with the increase in levels of CP. The weight gain, feed conversion ratio and specific growth rate improved to the level of estimated 31.57, 28.90 and 31.12% of CP, respectively. Quadratic effect was observed in levels of CP on body fat, body fat deposition, body protein deposition of body protein and nitrogen retention efficiency showing estimated minimum level, in the first two, 26.55; 23.77; and maximum estimated, on the others, of 29.26; 32.50; 27.21% PB, respectively. It was concluded that the recommendation of crude protein diets for tambaqui fingerling is 31.57%, which corresponds to a digestible energy ratio (DE): CP of 9.50 kcal of DE/g CP, by providing better weight gain. The second experiment was aimed at evaluate the effect of the reduction of crude protein (CP) of the diet with amino acids supplementation, based on the ideal protein concept in diets of tambaqui fingerlings. 750 fingerlings were used with initial weight 0.44 ± 0.14 g, in completely randomized design with six treatments, five repetitions and twenty five fish per experimental unit. The treatments has consisted of six isocaloric, isocalcic, isophosphoric and isolysinic experimental diets, containing different levels of CP (32.0; 30.5; 29.0; 27.5; 26.0 and 24.5%). With the reduction of the levels of PB after 27.5% PB, observed an improvement in weight gain, in specific growth rate, feed conversion and protein efficiency rate. Feed intake was higher than at level 26.0% of CP, followed by 29.0 and 27.5% of CP, and the remaining levels not varied among themselves. Crude protein consumption reduced with the use of smaller CP content of diet and carcass yield was not influenced by the treatments. The reduction in the protein content of the feed did not influence body composition, protein deposition and body fat. Nitrogen retention efficiency was higher in levels of 26.0 and 24.5% of CP. It is concluded that it is possible to reduction of from 32.0 to 24.5% the content for CP in diets for tambaqui fingerlings and that reduction of CP content for levels between 27.5 and 24.5% enhances the performance of the fish, since rations are supplemented with limiting essential amino acids.