Níveis de treonina digestível em dietas para panga (Pangasius hypophthalmus): desempenho, composição corporal e hematobioquímicas

Abstract

Threonine is one of the limiting essential amino acids in plant ingredients used in fish diets; its limitation can reduce fish development. The objective of this study was to evaluate the effect of digestible threonine levels in panga (Pangasius hypophthalmus) diets on performance, body composition and hematobiochemical variables. A total of 240 fish with an initial weight of 62g ± 0.64g were used. The treatments consisted of six isoproteic (25% crude protein) and isoenergetic (3700 kcal kg-1 gross energy) diets containing different concentrations of threonine, namely 8.70; 11.00; 13.60; 16.70; 19.30 and 21.60 g kg-1 of digestible threonine. The optimal level of digestible threonine was estimated at 13.80; 10.75 and 13.64 g kg-1 based on weight gain, feed conversion rate and specific conversion rate, respectively. For protein deposition and nitrogen retention efficiency, it was estimated at 15.66 g kg-1 of digestible threonine. For total liver protein content, it was 19.31 g kg-1 and for aspartate aminotransferase concentration, it was 15.42 g kg-1 of digestible threonine. It is concluded that the requirement of digestible threonine in panga diets is 15.66 g kg-1, because it promotes greater body protein deposition, without compromising the hematobiochemical parameters of the species.