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A 60-days feeding trial was conducted to delineate the effect of both gelatinized and non-gelatinized corn with or without supplementation with exogenous a-amylase at two dietary protein levels (35% and 28%) on dry matter digestibility, digestive enzymes and tissue glycogen content of Labeo rohita juveniles. Three hundred and sixty juveniles (average weight 10±0.15 g] were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets containing either 35% or 28% crude protein were prepared by including gelatinized (G) or non-gelatinized (NG) corn as carbohydrate source with different level of microbial a-amylase (0, 50, 100 and 150 mg kg -1 ). The dry matter digestibility of G corn fed groups was significantly higher (P < 0.05) than that of the NG corn fed groups. Hepatosomatic index (HSI), liver glycogen and intestinal amylase activity of G starch fed groups were significantly higher (P < 0.05) than those of the NG corn fed groups. However, the reverse trend was found for gastrosomatic index (GSI), muscle glycogen and intestinal protease activity. Addition of 50 mg a-amylase kg -1 feed improved the dry matter digestibility of NG starch fed groups, which was similar to that of the G corn fed groups or NG corn supplemented with 100/150 mg a-amylase kg -1 feed. HSI, liver glycogen and intestinal amylase activity were significantly increased (P < 0.05) at minimum level of a-amylase in the feed (50 mg kg -1 ) and did not increase due to further inclusion of amylase in the diet. Supplementation with a-amylase at 50 mg kg -1 increased the intestinal amylase activity beyond which no significant changes were observed. Protease activity of liver and intestine was highest (P < 0.05) in higher crude protein (CP) fed groups, but protease activity of the intestine was significantly higher in the a-amylase supplemented groups. Hence, it was concluded that feed with 28% CP containing either G corn without a-amylase or NG corn with 50 mg a-amylase kg -1 may be used as the alternative carbohydrate source for L. rohita juveniles.

A feeding trial was conducted for 60 days to delineate the effect of both gelatinized and non‐gelatinized corn with or without supplementation of exogenous α‐amylase at two level of protein 35% (optimum) and 27% (sub‐optimum) on growth, tissue composition and protein sparing effect of carbohydrate in the diet of Labeo rohita fingerlings. Three hundred and sixty fingerlings (average weight 10.00±0.15 g) were randomly distributed in 12 treatment groups with two replicates for each. Twelve semi‐purified diets containing either 35% or 27% CP were prepared with different levels of α‐amylase (0, 50, 100 and 150 mg kg−1) and starch type [gelatinized (G)/non‐gelatinized, (NG)] viz. T1 (NG, 35% CP, 0 mg kg−1α‐amylase), T2 (G, 35% CP, 0 mg kg−1α‐amylase), T3 (NG, 27% CP, 50 mg kg−1α‐amylase), T4 (NG, 35% CP, 50 mg kg−1α‐amylase), T5 (G, 27% CP, 50 mg kg−1α‐amylase), T6 (G, 35% CP, 50 mg kg−1α‐amylase), T7 (NG, 27% CP, 100 mg kg−1α‐amylase), T8 (NG, 35% CP, 100 mg kg−1α‐amylase), T9 (G, 27% CP, 100 mg kg−1α‐amylase), T10 (G, 35% CP, 100 mg kg−1α‐amylase), T11 (NG, 27% CP, 150 mg kg−1α‐amylase) and T12 (NG, 35% CP, 150 mg kg−1α‐amylase). The fish were acclimatized to the experimental condition for 24 days during which control diet (NG, 35% CP) was fed. Weight gain percentage, specific growth rate, protein efficiency ratio and apparent net protein utilization of NG corn‐fed groups at 42.43% were significantly higher (P<0.05) than the same level of G corn‐fed groups. We conclude that 42.43% NG corn supplemented with 50 mg α‐amylase kg−1 feed at sub‐optimum level of CP (27%) significantly enhanced the growth and protein in L. rohita fingerling. Addition of dietary α‐amylase to G corn had no added advantage on growth of L. rohita fingerling.