Effect Of L-arginine And N-carbamylgluatmate On Small Intestinal Villi Development And Cecal Microbiota Composition Of Young Rabbits

As an essential amino acid,arginine,which in actual production is constantly supplemented with L-arginine（L-Arg）and its internal biomass N-carbamoylglutamic acid（NCG）,plays an important role in the growth and development of animals.Being a herbivore,rabbits are influenced potentially at their growth and development by the cecal microbiota,on which the study on whether the addition of L-Arg and NCG has an effect is limited.Therefore,this experiment studies the effects on the phased production performance,small intestinal histology and cecal microbiota of JWR young rabbits by adding L-Arg and NCG to the feed of Japanese rabbits（JWR）in the hoping of analyzing the mechanism of L-Arg and NCG on the regulating of cecal microbiota and individual health.In this study,18 normal-grade male JWR that were weaned at 30 days and in good physical condition are randomly divided into contrast group（basic diet）and arginine group（basic diet+0.5%L-arginine）,and NCG group（basic diet+0.5%NCG）.We put the experiment subjects at feeding stage of 65 days and 85 days to death and collected and analyzed their feces,urine,blood,intestinal tissues and intestinal contents.The results are as follows:1.After eating diet with L-Arg and NCG,the young rabbits gained their daily weight and the serum growth hormone levels and total protein content and IgM content increased significantly,urine nitrogen content was significantly decreased,while there were no significant changed in digestive nitrogen,apparent digestibility,feed conversion ratio,serum urea nitrogen and spleen index.The cholesterol content and IgA had grown markedly with the addition of L-Arg Specifically,in Arginine group and NCG group of 65 day-old,the feed intake,fecal nitrogen,residual nitrogen,IgG and thymus index of the young rabbits were significantly higher than those in control group（P < 0.05）,and the nitrogen intake,net protein utilization rate,biological value were all significantly increased（P < 0.01）.In L-Arginine group and NCG group of 85 day-old,the young rabbit’ average daily feed intake,nitrogen intake,net protein unilization and IgA were significantly increased（P < 0.01）,and the fecal nitrogen,biological value,and IgG had increased remarkably（P < 0.05）while there was no sharp change in thymus index（P > 0.05）.2.The jejunum villus heightened and the crypt deepended in the L-Arg and NCG rabbits at 65 days old（P < 0.05）,The addition of NCG increased the ileal villus height and villus height to crypt depth in young rabbits（P < 0.05）.The crypt depth was significantly decreased（P < 0.05）,and there was no significant change in the L-Arg group（P > 0.05）.Compared to the contrast group,jejunum villus height was significantly higher in the 85-day-old L-Arg and NCG groups（P < 0.05）,there was no significant change in the crypt depth,villi height and crypt depth ratio（P > 0.05）.The ileal villi height increased significantly while the crypt depth decreased significantly（P < 0.05）,and there was no significant change in the ratio of villi height to crypt depth and the control group（P > 0.05）.3.A total number of 10 bacteria were found in the cecum of rabbits of different age groups.The dominant bacteria（abundance>1.0%）were Firmicutes,Bacteroidetes,Proteobacteria,Verrucomicrobia and Tenericutes,amounting to more than 98.5% of the total abundance.At the genus level,a total of 22 genera were found,each of which was different from the different treatment genus: at 65 days of age,Parabacteroides in the L-Arg group were largely reduced compared with the contrast group（P < 0.05）;in the NCG group,Ruminococcaceae_V9D2013_group（P < 0.01）,Ruminococcaceae_UCG-005,Parasutterella,Subdoligranulum were clearly reduced（P < 0.05）,and Ruminiclostridium₁ and Roseburia gained their sharp growth（P < 0.05）.Christensenellaceae_R-7_group 、 Celria and the Ruminococcaceae_UCG-001 in the L-Arg group were more than it in the NCG group（P < 0.05）,and the Enterobacteriaceae was less.（P < 0.05）;in the 85-dayold,compared to the contrast group Clostridiales_bacterium reduced（P < 0.05）and the Anaerovorax increased（P > 0.05）in L-Arg group,while the Bacteroides（P < 0.05）and Alistipes reduced（P < 0.01）and Hydrogenoanaerobacterium,Tyzzerella₃ and（[Eubacterium]_ruminantium_group）increased（P < 0.05）in NCG group.The comparison between the two groups showed that the two strains of the NCG group,Alistipes（P < 0.01）and Family_XIII_AD3011_group（P < 0.05）,were lower than the young rabbits abundance in the L-Arg group.4.The addition of L-Arg and NCG can up-regulate the expression levels of EGF,IGF1,GHR,Occluding,ZO-1,CAT1,EAAT3,FATP4,PEPT1,SLC6A19,AGRP and NPY in the small intestine;down-regulate the expression of FAS,P53,HO-1,NRF2,CART,CCK,in addition,it can up-regulate the expression levels of EGF,IGF1,GHR,Occluding,ZO-1 and down-regulate the expression levels of FAS,P53,HO-1,NRF2,LKB1,NF-κB,IL-1α,TNFα and TLR4 in the cecum.During this process,Parasutterella 、 Ruminococcaceae_UCG-005 、 Anaerotruncus and Christensenellaceae_R-7_group have strong positive or negative correlations with the expression the these genes,which may affect the growth and development of young rabbits by affecting intestinal growth,immunity,and intestinal nutrient transport.In conclusion,the diets with L-Arg and NCG for baby JWR have improved their production performance and immune function with the better growth and development of jejunum and ileum.The outcomes indicate that the two additives generated great impacts on nutrient utilization,anti-inflammatory and adaptation strengthening,but LArg and NCG have different effects on some biological traits including intestinal bacterial flora.The results of the research will provide theoretical basis either for the L-Arg and NCG spread and application in the field of feed additives or the exploration to change the production performance of animal organisms through the abundance and composition of intestinal flora and its metabolic pathways,additionally establishing a nutrient-intestinal flora-host between the association.