Dietary threonine requirement of fingerling Channa punctatus (Bloch) based on growth, feed conversion, protein retention efficiency, hematological parameters, and biochemical composition

Abstract

Six isonitrogenous and isocaloric purified diets with different threonine concentrations (5, 10, 15, 20, 25, and 30 g kg−1) were fed to triplicate groups of Channa punctatus (6.24 ± 0.07 g) for 12 weeks to estimate dietary threonine requirement. Absolute weight gain, protein and threonine retention efficiency, feed conversion ratio and RNA/DNA ratio of trial diets with incremental threonine concentrations improved up to 20 g kg−1 dry diet. Carcass protein and moisture contents increased up to 20 g kg−1 dietary threonine. However, carcass fat also showed a reverse pattern, increasing threonine concentrations up to a 20 g kg−1 dry diet. Hemoglobin (Hb), red blood corpuscles (RBCs) and hematocrit (Hct) value improved significantly (p < .05) up to 20 g kg−1. Total serum protein, superoxide dismutase (SOD), catalase (CAT), and lysozyme was found to increase significantly up to 20 g kg−1 dry diet, and a significant fall was recorded at a higher threonine level (Th30). Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) concentrations declined significantly with dietary threonine levels up to 20 g kg−1. Quadratic regression analysis of absolute weight gain, feed conversion ratio, protein, and threonine retention efficiency data against incremental threonine levels projected the optimum requirement between 22.2 and 23.0 g kg−1 dry diets.