FEEDING OF VARIOUS CARBOHYDRATE SOURCES ON THE GROWTH-PERFORMANCE AND NUTRIENT UTILIZATION IN OREOCHROMIS-NILOTICUS

Five isonitrogenous and isocaloric diets containing different types of carbohydrates (maize grain, starch, dextrin, sucrose and glucose) at 25 % level were prepared and fed to fingerling Oreochromis niloticus (average weight 23.34 g +/- 0.56 g) for a period of 70 days. Significant differences were observed in the weight gain, feed consumption, feed conversion ratio (FCR, as Kg feed consumed per Kg weight gain), specific growth rate (SGR, as percentage of body weight gain per day), protein efficiency ratio (PER, as g liveweight gain per g protein consumed) and net protein retention (NPR, as [increase in carcass protein/protein fed] x 100) of fish fed various carbohydrate diets. The diet containing maize grain showed the best performance in terms of weight gain, FCR, 1.12; SGR, 1.062 %; PER, 1.92; and NPR, 31.76 %, while the glucose diet gave the poorest results (FCR, 2.07; SGR, 0.635 %; PER, 1.11 and NPR, 16.74 %). The source of carbohydrate in the diet also affected the proximate chemical composition of the fish filet, liver and carcass. The crude protein content of fish carcass increased whereas the fat and gross energy contents decreased as compared to control (fish slaughtered at the beginning of the experiment). Similar results were obtained for crude protein and fat contents of fish filet. The source of carbohydrate however, did not affect (P<0.05) the crude protein content of fish filet. The dry matter and nitrogen free extract (NFE) contents of the liver decreased whereas the crude protein increased on carbohydrate diets as compared to control. The fish fed glucose diet showed lower crude protein but higher NFE values in the liver as compared to those fed maize grain and starch diets. The role of carbohydrate source in fish diets in relation to growth performance and body composition is discussed.