The Effect Of Small Peptides By Casein On Nutritive Physiology In Grass Carps

225 grass carps with average weight 3.74±0.23g were used in an experiment to investigate the effect of small peptides in diet on performance of grass carps. The grass carps were divided into three groups and fed in 3×3 aquatic cases (0.25m3 versus 25 grass carps) for 56 days. The diets of test group 1, 2 and control group included in 0.5% enzymatic casein (small peptides above 80% and average length of peptides is 2.98), 0.5% acidify hydrolyzed casein(free amino acids above 80% ) and 0.5% casein. The experiment results showed that the relative growth rates (RGR), feed modulus (FM), protein reservation rate (PRR), contents of magnesium and small peptides in plasma on grass carps in 0.5% enzymatic casein group were significantly higher than those in 0.5% casein group and 0.5% acidify hydrolyzed casein group(p<0.05) . These results suggested that small peptides could improve the rates of apparent digestibility and protein digestibility and increase the total amount of small peptides in blood circulation and the retention of nitrogen in body, accordingly reducing the store of fat in hepato-pancreas and mesentery, accordingly to improve the utilization of amino acids in diet.