Effect of dietary l-lysine levels on growth, feed conversion, lysine retention efficiency and haematological indices of Heteropneustes fossilis (Bloch) fry

Effect of varying dietary lysine levels on growth, feed conversion, nutrient retention, lysine retention efficiency and haematological indices of Heteropneustes fossilis fry (2.97 ± 0.11 cm; 4.78 ± 0.31 g) was studied by conducting a 12-week feeding trial. Isonitrogenous (450 g kg−1 CP) and isocaloric (17.97 kJ g−1 GE) amino acid test diets with graded concentrations of l-lysine (18, 20, 22, 24, 26, 28 g kg−1 dry diet) were fed to triplicate groups of fish to apparent satiation twice daily at 17 and 17:30 h. Maximum thermal growth coefficient (TGC, 0.82), best feed conversion ratio (FCR, 1.28) highest protein retention efficiency (PRE, 36%), energy retention efficiency (ERE, 79%) and lysine retention efficiency (LRE, 75%) were noted at 24 g kg−1 lysine of dry diet. Body protein was also found to be in line with growth data and peaked at 24 g kg−1 lysine of dry diet. Similarly, superior somatic and haematological indices were exhibited by the groups fed dietary lysine at 24 g kg−1 of the dry diet. However, exponential analysis of dietary lysine intake against TGC, lysine retention and protein retention indicated that inclusion of dietary lysine in the range of 13.24–14.14 g kg−1 dry diet, corresponding to 29.42–31.42 g kg−1 dietary protein, is essential for faster growth of this fish.