Utilization of different carbohydrates at different dietary protein levels in grass prawn, Penaeus monodon, reared in seawater

Abstract

To investigate the utilization of different carbohydrate sources and the possible substitution of carbohydrate for dietary protein for grass prawn, Penaeus monodon, reared in seawater, nine approximately isocaloric semipurified diets were prepared. Three dietary protein levels (40, 35, 30%) were achieved by substitution with three levels (20,25, 30%) and three sources (glucose, dextrin, starch) of dietary carbohydrate. Results indicated that prawns fed starch or dextrin had significantly ( P < 0.05) better weight gain, feed efficiency ratio (FER) and protein efficiency ratio (PER) than those fed glucose. Prawn fed starch showed significantly higher ( P < 0.05) weight gain, FER and PER than those fed 30% dextrin. Survival rates of prawn fed starch and dextrin were higher ( P < 0.05) than of those fed glucose. The post-prandial blood-sugar level peaked earliest in prawns receiving glucose, followed by those fed dextrin and finally by those fed starch. Protein deposition was high in prawns fed starch, intermediate in prawns fed dextrin and low in prawns fed glucose. These data suggest that carbohydrate utilization in P. monodon is highest when the source is starch followed by dextrin and finally by glucose. Decreasing the dietary protein level from 40 to 30%, by increasing the starch content in the diet from 20 to 30%, did not reduce ( P > 0.05) weight gain, FER or survival rate suggesting that starch spared some dietary protein in this species.