Effect of feeding raw soybean meal on growth, nutrient utilization, and amylase and protease activity of Indian major carp (Catla catla) fry was studied in a 70-day feeding trial. Five isocaloric (1568 kJ/100 g diet) and isonitrogenous (45 g crude protein/100 g diet) semi-purified diets had varying levels of soybean meal (0, 5, 10, 20 or 30%). Ninety C. catla fry (0.94±0.02 g) were distributed into the five treatment groups with three replicates of each treatment. The weight gain, SGR, and PER of groups receiving diets with soybean meal were significantly (p<0.05) lower than in the control group that contained no soybean meal. Trypsin inhibitor units in the diets negatively correlated with weight gain (r= -0.7557), protein digestibility (r = -0.9541), trypsin (r = -0.9087) and protease activity (r = -0.8596), and positively correlated with carbohydrate digestibility (r = 0.8140) and amylase activity (r = 0.7802). An increase of trypsin inhibitor units resulted in increased hypertrophy of pancreatic, kidney, and liver tissues. Inclusion of as little as 5% soybean meal depressed the growth rate. Hence, although the soybean diets did not result in mortality, inclusion of raw soybean meal in the diet of C. catla fry should be discouraged.
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