Interactive Effects of Dietary Starch Levels and Exogenous α-Amylase on Growth, Digestibility, and Metabolic Responses in Channa striata Juveniles

A 70-day feeding trial was carried out to examine the effects of exogenous alpha amylase supplementation and different levels of starch on the growth performance, whole-body proximate composition, apparent nutrient digestibility, and digestive and metabolic enzyme activities of Channa striata juveniles. Nine semi-purified iso-nitrogenous (42%) and iso-lipidic (7%) diets containing three different levels of starch (viz. 10%, 20% and 30%) and amylase (0%, 0.05%, 0.1%) were formulated as C10A0, C10A0.05, C10A0.1, C20A0, C20A0.05, C20A0.1, C30A0, C30A0.05, and C30A0.1 (C-starch, A-amylase). A total of 405 C. striata juveniles of average weight (14.31 ± 0.1 g) were randomly assigned to 27 150 L capacity FRP tanks with 15 fish per tank following a 3 × 3 factorial design in triplicate with proper aeration. Final weight, weight gain (WG%), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) were significantly influenced (p < 0.05) by dietary starch and amylase supplementation as well as their interaction. The nutrient digestibility results revealed that the apparent digestibility coefficient of dry matter, crude protein, crude lipids, and carbohydrates improved significantly (p < 0.05) with higher amylase levels. There was no significant variation (p > 0.05) in the whole-body proximate composition of fish fed with different levels of starch and exogenous amylase supplementation. Amylase activity increased with higher dietary amylase levels; however, there were no significant differences in protease and lipase enzyme activity. Fish in the A0.1 treatment group had significantly higher (p < 0.05) hexokinase activity, which was significantly affected by exogenous amylase levels. AST and ALT activities in the serum were decreased (p < 0.05) at 0.1% amylase inclusion in the diet. From the present study, it is concluded that supplementation with exogenous alpha amylase has the potential to enhance starch utilization in C. striata. In particular, 0.1% amylase with 20% starch can significantly improve growth and nutrient utilization in C. striata juveniles without adverse effects.