Effects Of Dietary Soybean Protein Peptide Levels On Production Performance, Digestion And Immune Function Of Oncorhynchus Mykiss

In this study,Oncorhynchus mykiss was used to study the effects of different levels of small peptides on the growth performance,digestion and immune function of rainbow trout.Seven thousand two hundred rainbow trout with average weight at 163.5 ± 5.3g were randomly allocated into four treatments.Each treatments had 3 replicate groups and each replicate groups contained 600 fish.The four treatments were basal diets with 0%small peptides(Group ?),1%small peptides(Group ?),2%small peptides(Group ?)and 4%small peptides(Group ?).After experimental period of 60 days,blood and other tissues were collected.Growth performance,indices of the head,spleen,liver,anterior and posterior intestine were calculated.The test results are as follows:(1)Compared with group ?,the weight of the group ? was significantly increased by 8.8%(P<0.05)and the specific growth rate was significantly increased by 5.8%(P<0.05).The dietary coefficient of group ? was significantly lower than that of group ?(P<0.05,decreased by 3.1%),and the effect of growth was dose-dependent.(2)Compared with group ?,villus heights of the front,middle and posterior intestine in group ? were significantly higher than that of the group ?(P<0.05),which increased by 23%,10.7%,10.4%,respectively.The Crypt depth of group ? were decreased significantly by 14%,7%and 14.5%(P<0.05).The goblet cells density of anterior and posterior intestine were also significantly increased by 34%and 39%,respectively(P<0.05).Group ? had the highest goblet cells density.The levels of intestinal chymotrypsin,creatine kinase and Na~+-K~+-ATPase were also significantly increased by 9.8%,16.3%%,10.9%(P<0.05)and group ? had the highest levels.There was no significant difference in lipase and amylase(P>0.05).(3)Compared with group ?,the spleen index,levels of IgM,C3,C4 and lysozyme in group ? were significantly increased by36.8%,20.9%,26.9%,20.9%and 20.8%,respectively(P<0.05).The relative expression of SOD and defensin in the head kidney,liver and spleen were significantly increased(P<0.05),the total antioxidant capacity was also significantly increased(P<0.05),while the contents of lymphocytes,hemoglobin,head kidney and intestinal protein were not significantly changed(P>0.05).In this study,under the experimental conditions,4%dietary small peptides intervention could improve the growth performance and dietary utilization rate,promote intestinal growth and development,enhance the activity of intestinal digestive enzyme and nutrient absorption capacity,and stimulate immune function.