Exigência de valina digestível em dietas para tambaqui com diferentes pesos corporais

Abstract

Valine is an essential amino acid belonging to the group of branched chain amino acids along with leucine and isoleucine and has physiological functions such as regulation of translation and initiation of protein synthesis. The tambaqui (Colossoma macropomum) stands out as the main native species most produced in the country, but information on valine requirements is still lacking. The objective was to determine the digestible valine requirements for tambaqui with different body weights. 720 tambaquis were used in two experiments, one with 360 fish with an initial body weight of 33.28±0.19g and the other with 360 fish with an initial weight of 121.19±1.29g. Both experiments were distributed in a completely randomized experimental design (DIC), consisting of five treatments, four replicates and 15 fish per experimental unit, and lasted for 50 days. The treatments consisted of five experimental diets with levels of 0.50; 0.70; 0.90; 1.10 and 1.30% digestible valine. The fish were kept in polyethylene boxes equipped with water supply and individual aeration, and fed freely for six meals a day. Performance parameters, body composition, daily protein, fat and body ash deposition rates and body nitrogen retention efficiency were evaluated. Feed intake did not change and digestible valine intake increased linearly as a function of the increase in valine levels in both experiments. For the weight gain and specific growth rate, a linear increase was observed for the body weight of 33g and a quadratic effect for the body weight of 121g, increasing this variable to 0.92 and 0.94% valine levels digestible, respectively. Feed conversion showed a quadratic effect for both body weights, reducing the value of this variable to the level of 1.17 and 0.93%, respectively. Dry matter, moisture and ash contents were not affected by treatments for body weight of 33g and had a linear effect for dry matter and moisture for animals with body weight of 121g. The levels of protein and body fat had a quadratic effect with an estimated level of 1.07 and 0.90%, and 1.07 and 0.10% of digestible valine for animals with body weights of 33 and 121g, respectively. For 33g animals there was a quadratic increase for the variables body protein deposition, body fat deposition and nitrogen retention efficiency up to levels estimated at 1.19, 0.94 and 0.94% of digestible valine, respectively. For 121g animals there was a quadratic increase for body protein deposition and nitrogen retention efficiency up to levels estimated at 0.91 and 0.82% of digestible valine, respectively. It is concluded that the dietary digestible valine requirement for tambaqui with a body weight of 33 g to 83 g is estimated at 1.19% and for tambaqui with a body weight of 121g to 277 g is 0.91%, as it provides greater deposition of body protein.