Gelatinized to non-gelatinized starch ratio in the diet of Labeo rohita: effect on digestive and metabolic response and on growth.

A 60-days experiment was conducted to study the optimum gelatinized (G) to non-gelatinized (NG) starch ratio in the diet of Labeo rohita juveniles with respect to digestive and metabolic response and on growth. Two-hundred and thirty-four juveniles (avg. wt 2.53 +/- 0.04 g) were randomly distributed in six treatment groups with each of three replicates. Six semipurified diets either containing NG and/or G corn starch viz., T(1) (100% NG, 0% G starch), T(2) (80% NG, 20% G starch), T(3) (60% NG, 40% G starch), T(4) (40% NG, 60% G starch), T(5) (20% NG, 80% G starch) and T(6) (0% NG, 100% G starch) were prepared. The dry matter digestibility and carbohydrate digestibility were highest (p < 0.05) in T(6) group and lowest in T(3) and T(4) groups. The amylase activity in intestine increased as G:NG level increased in the diet. Protease activity in intestine was highest in T(6) group and lowest in T(1) group. Similar trend was recorded for specific growth rate, protein efficiency ratio and apparent net protein utilization. Liver glycogen, hepatosomatic index and blood glucose level increased linearly with the increasing level of G starch in the experimental diet. The results indicate that higher nutrient digestibility and growth was recorded either at low (20% G starch, T(2)) or high (100% G starch, T(6)) G starch fed group. But high G starch fed group (T(6)) exhibits higher liver glycogen and blood glucose level, which may lead to stress due to long-term feeding. Hence, it is suggested that 20% G and 80% NG starch is optimum for better nutrient digestibility and growth in L. rohita juveniles.