Effects Of Exogenous Xylanase Supplementation In Diets On Growth Performance, Intestinal Enzyme Activities, Microflora And Immune Ability Of Juvenile Jian Carp (Cyprinus Carpio Var. Jian)

A total of900juvenile Jian carp were randomly assigned to six group with three replicate, each replicate has50fish, the fish weight were7.99±0.02g. The juvenile Jian carp were fed diets containing graded levels of xylanase at220(unsupplemented control),650,1070,1480,1810and2470U kg-1diet for10weeks to investigate the effects exogenous xylanase supplementation in diets on growth performance, the activities of intestinal enzyme, microflora and immune ability. After the growth trial, this challenge trial lasts for17days.The results showed that xylanase great significantly inhanced percent weight gain, protein efficiency ratio, feed efficiency and nutrition production value (P<0.01). The significant positive correlation existed between PWG and FI and FE (r1=+0.975, P＜0.01; r2=+0.991, P<0.01). These data indicated that xylanase improved growth by increasing FE and FI. FE was also positively correlated with PPV, LPV, CPV and NR (r1=+0.997, P＜0.01; r2=+0.996, P＜0.01; r3=+0.999, P<0.01; r4=+0.995; P<0.01). These appeared that xylanase improved FE through promoting the utilization of nutrition. Similarly, the activities of the y-glutamyl transpeptidase, creatinekinase, alkaline phosphatase and Na+, K+-ATPase in all segment intestines. The chymotrypsin, amylase, trypsin, lipase activities in intestine and hepatopancreas were improved by xylanase. The amounts of Lactobacillus, Escherichia coli and Aeromonas were significantly affected by dietary xylanase levels (P<0.05). At the same time, xylanase improved immune ability through inhanced thevaccinated survival rate, the content of addiment C3, lysozyme acitivity and IgM content of intestine, serum,spleen and kidney (P<0.05).In conclusion, the present results indicated that xylanase supplementation improved growth performance, enhanced digestive and brush border enzyme activities and changed the amount of intestinal microflora. Xylanase also has the ability to inhanced the immunity ability. The optimal supplemental level of xylanase in juvenile Jian carp (7.99-99.16g) based on PWG was1258U kg-1diet by the quadratic regression analysis.