Effects Of Soybean Antigen Protein Glycinin On Growth,Antioxidant Capacity And Intestinal Tissue Of Rhynchocypris Lagowskii Dybowski

Soybean protein source had the characteristics of high protein content,balanced amino acid composition and low price.It was considered as a high-quality substitute for fish meal.However,due to the presence of anti-nutritional factors(ANFs),excessive use of soybean protein sources in feed could cause growth retardation and health deterioration of aquatic animals.Soybean antigenic protein glycinin was one of the main ANFs in soybean protein source and had strong immunogenicity.Therefore,this study was to evaluate the effects of glycinin on the growth,antioxidant capacity and intestinal morphology of juvenile Rhynchocypris lagowskii Dybowski.Five isonitrogenous and isolipidic diets were formulated which containing glycinin at 0 g/kg(CK group),10 g/kg(G-1 group),20 g/kg(G-2 group),40 g/kg(G-4 group),and 80 g/kg(G-8group),respectively.Then the Rhynchocypris lagowskii Dybowski with an initial body weight of[(4.61±0.02)g/tail] were fed these diets for 8 weeks.After the end of feeding trial,the growth,physiological and biochemical indexes were measured,and the expression of inflammation and antioxidation related genes in intestine and hepatopancreas were measured by quantitative real-time PCR.The experimental results were to explore the damage mechanism of glycinin to aquatic animals and determine the threshold of glycinin in compound feed of Rhynchocypris lagowskii Dybowski,which was of great significance for the rational development and utilization of soybean protein source and healthy culture of Rhynchocypris lagowskii Dybowski.1.Effects of glycinin on the growth performance and nutritional composition of Rhynchocypris lagowskii Dybowski.Under the conditions of our experiment,compared with CK group,the weight gain rate(WGR),specific growth rate(SGR),final body weight and whole-body crude protein content of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups were significantly decreased(P<0.05),while the whole-body water content was significantly increased(P<0.05).The feeding rate(FI),feed efficiency rate(FER),protein efficiency rate(PER)and muscle crude protein content were significantly decreased(P<0.05),while the muscle water content was significantly increased(P<0.05).2.Effects of glycinin on the activities of digestive enzyme and protein metabolism enzyme of Rhynchocypris lagowskii Dybowski.Under the conditions of our experiment,the protease activity in all intestinal segments of G-4 and G-8 groups was significantly decreased than CK group(P<0.05),and the protease activity of hepatopancreas in G-8 group was significantly decreased than CK group(P<0.05);glycinin had no significant effect on lipase and amylase activities(P>0.05).Compared with CK group,the activity of alanine aminotransferase(ALT)in hepatopancreas of G-4 and G-8 groups was significantly decreased(P<0.05),and the activity of aspartate aminotransferase(AST)in hepatopancreas of G-8 group was significantly decreased(P<0.05);while the serum ALT and AST activities of Rhynchocypris lagowskii Dybowski of G-8 group were significantly increased(P<0.05).3.Effects of glycinin on the immune function and expression of inflammation-related genes of Rhynchocypris lagowskii Dybowski.Compared with CK group,the activities of lysozyme(LZM)and alkaline phosphatase(AKP),the content of complement 3(C3)and immunoglobulin M(Ig M)in serum of G-4 and G-8 groups were significantly decreased(P<0.05);serum complement 4(C4)content of Rhynchocypris lagowskii Dybowski of G-8 group was significantly decreased(P<0.05).Compared with CK group,the m RNA expression of interleukin-1β(IL-1β)in hepatopancreas and distal intestine(DI),and TNF-α in hepatopancreas,mid intestine(MI)and DI of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups was significantly increased(P<0.05);the m RNA expression of tumor necrosis factor-α(TNF-α)in proximal intestine(PI),IL-1β in MI of Rhynchocypris lagowskii Dybowski of G-8 group was significantly increased(P<0.05).Compared with CK group,the m RNA expression of interleukin-10(IL-10)in DI,and transforming growth factor-β(TGF-β)in hepatopancreas of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups was significantly decreased(P<0.05);the m RNA expression of TGF-β in MI and DI,IL-10 in hepatopancreas and MI of Rhynchocypris lagowskii Dybowski of G-8group was significantly decreased(P<0.05).4.Effects of glycinin on the antioxidant capacity and related genes expression of Rhynchocypris lagowskii Dybowski.Under the conditions of our experiment,compared with CK group,malondialdehyde(MDA)content in hepatopancreas,MI and DI of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups was significantly increased(P<0.05),and MDA content in PI of G-8 group was significantly increased(P<0.05);the activities of glutathione peroxidase(GPx)and total superoxide dismutase(T-SOD)in hepatopancreas,MI and DI,catalase(CAT)in DI of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups were significantly decreased(P<0.05);the activities of CAT in hepatopancreas,PI and MI,GPx and T-SOD in PI of Rhynchocypris lagowskii Dybowski of G-8 group were significantly decreased(P<0.05).Compared with CK group,kelch-like ECH-associated protein-1(Keap1)m RNA expression in MI and DI of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups was significantly increased(P<0.05),and Keap1 m RNA expression in PI of G-8 group was significantly increased(P<0.05);GPx m RNA expression in DI of Rhynchocypris lagowskii Dybowski of G-2,G-4 and G-8 groups was significantly decreased(P<0.05);the m RNA expression of nuclear factor erythroid-2 related factor 2(Nrf2)and CAT in hepatopancreas and DI,Keap1 in hepatopancreas,heme oxygenase-1(HO-1)in hepatopancreas,MI and DI,GPx in hepatopancreas and MI of Rhynchocypris lagowskii Dybowski of G-4 and G-8 groups was significantly decreased(P<0.05);the m RNA expression of HO-1 and GPx in PI,Nrf2 in PI and MI,CAT in MI of Rhynchocypris lagowskii Dybowski of G-8 group was significantly decreased(P<0.05).5.Effects of glycinin on the intestine tissues of Rhynchocypris lagowskii Dybowski.Under the conditions of our experiment,compared with CK group,mucosal fold height in MI and DI,muscle layer thickness in DI of Rhynchocypris lagowskii Dybowsk of G-4 and G-8groups were significantly decreased(P<0.05);mucosal fold height in PI,muscle layer thickness in PI and MI of G-8 group were significantly decreased(P<0.05);while the lamina propria width in DI of Rhynchocypris lagowskii Dybowsk of G-8 group was significantly increased(P<0.05).The morphological structure of mucosal fold in PI,MI and DI of Rhynchocypris lagowskii Dybowsk of CK group was complete,the nucleus of the intestinal mucosal epithelial cells were arranged tightly and neatly,the muscle layer was thick,and the mucosal fold developed well.However,partial epithelial mucosa was separated from the lamina propria in PI of G-8 group.Disordered nucleus arrangement of intestinal epithelial mucosal cells,separation of epithelial mucosa from lamina propria,atrophy and damage of mucosal fold were observed in MI and DI of Rhynchocypris lagowskii Dybowsk of G-4 and G-8 groups.In summary,the additional amount of glycinin should not exceed 40 g/kg in the compound feed of Rhynchocypris lagowskii Dybowski.