EFFECT OF DIETARY SMALL PEPTIDES ON GROWTH PERFORMANCE OF GRASS CARP, CTENOPHARYNGODON IDELLA

The experiment was conducted to determine the effect of dietary small peptides on growth performance of grass carp Ctenopharyngodon idella. 450 grass carp(initial weight ca.3.70g) were divided into 6 experimental triplicate groups and fed inaquatic cases(25 grass carp 0. 25m3) by a recirculated filtered rearing system maintained for 56 days at 27.6±3. 1℃.The diets of control group included in 1% fish meal and test group 1, 2,3, 4,5 included in 0. 25%, 0. 5%, 1% protein-peptides by shrimp waste, 0. 5% Hydrolyzed fish meal as small peptides and 0. 5% enzymatic casein as three different kinds of small peptides.The experimental results showed that the survival ratio (SR) of fish in all experimental groups were similar, but the relativegrowth ratio (RGR), feed conversion ratio(FCR) and protein retention ratio(PRR) of fish in test group 2, 3, 4 and 5 were significantly better than fish in control group(P0. 05).The ratio of hepatopancreas/body, bowel/body, fat in mesentery/body and the amount of fat on hepatopancreas in fish by all test groups were significantly or very significantly lower than control group (P<0. 05) or(P<0.01). In the body composition, content of lipid on all test groups was significantly higher than fish by control group(P<0.05).The feasible amount of protein-peptides from shrimp waste in diet of grass carp was 0. 5% in diet.These results indicated that varied dietary small peptides could increasethetotal amount of small peptides in blood serumand improve the both ratio of apparent digestibility and protein digestibility. Accordingly to advance the utilization of dietary protein and reduce the store of fat in hepatopancreas, mesentery and body, fish fed diets with three kinds of small peptides increased the ability of nitrogen sediment and protein compound in body.Thereby dietary small peptides could affect utilization of dietary protein and improve the growth performance in grass carp. The dietary peptides provided not only amino acids as materials of protein compound in fish body,but also active biologic small peptides whose could pay an positive role on the process of dietary digest and utilization.