Effect Of Dietary Tributyrin In High Cottonseed And Rapeseed Meal Diets On Immune And Intestinal Health Of Grass Carp(Ctenopharyngodon Idella)

Two experiments were conducted to investigate whether tributyrin(TB)could alleviate the negative effects of high cottonseed and rapeseed meal on growth,immunity and intestinal health of juvenile grass carps.Experiment 1:set the base diet group(S1),the high cottonseed and rapeseed meal diet(S2),and added 500(S3),1000(S4),and 1500 mg/kg(S5)TB in the cottonseed and rapeseed meal diet,each group set up three repeats,and 50 tail grass carp(9.59±0.01)g per repeat.The experiment were conducted in cages(2×2×2m)for10 weeks.Experiment 2:set the high cottonseed and rapeseed meal diet as the basis feed,and added 300,600,and 1000 mg/kg TB to the basis feed,named T0,T300,T600 and T1000,respectively.A total of four groups with 3 replicates per group and 40 tail grass carp(20.04±0.19)g per replicate.The feeding test lasted for 8 weeks to research TB if relief immune stress reaction of grass carp after LPS stimulation.The results shown that:1.Effects of TB on growth and serum biochemical indices of juvenile grass carps fed with high cottonseed and rapeseed meal dietsCompared with the S1 group,the WGR,SGR and intestinal amylase activity of grass carps were significantly decreased and the serum TG content was significantly increased in the S2 group.Compared with the S2 group,the WGR,SGR and intestinal digestive enzymes activity were improved to a certain extent,the body index first increased and then decreased,serum total cholesterol content was significantly decreased,and TG content decreased after adding TB.In addition,the WGR and SGR in the S4 group were not significantly different from that of the S1 group.There were no significant difference in the body composition,serum glucose,total protein,albumin and urea nitrogen contents among groups.2.Effects of TB on intestinal barrier of juvenile grass carps fed with high cottonseed and rapeseed meal dietsCompared with the S1 group,the serum SOD,C3,AKP,GPx activities,intestinal AKP,Na~+-k~+-ATP,NO contents and mid-intestinal villus height,and V/C,and hind-intestinal muscular thickness were significantly decreased,the m RNA expression of IL-10,TGF-β,IκBα,ZO-2 and Claudin-b were significantly downregulated,and serum GPT activity,mid-intestinal crypt depth,hind-intestinal V/C value and crypt depth,intestinal IL-1β,IL-6,IL-8,TLR-4,Claudin-12,and MLCK m RNA levels were all significantly increased in the S2group.Compared with the S2 group,the activities of SOD,T-AOC,C3,C4,IgM,AKP and GPx and intestinal Na~+-k~+-ATP and CK in the serum showed an increasing,and the activities of GOT and GPT had a decreased trend after TB adding.In addition,the AKP,NO contents and intestinal crypt depth,V/C value,muscular thickness were significantly increased.Moreover,the m RNA expression of IL-6,IL-8,NF-κB,Claudin-12 and MLCK in the S4group were significantly downregulated,and the IL-10,IκBα,Claudin-c,Occludin and Claudin-b were significantly upregulated compared to the S2 group.3.Effects of TB on intestinal flora of juvenile grass carps fed high cottonseed and rapeseed meal dietsThe species quantity and richness of intestinal flora in the S2 group increased compared with the S1 group.The addition of 1000 mg/kg TB reduced the species quantity and richness,which was close to the S1 group.At the level of phylum,the richness of Firmicutes and Bacteroidetes increased significantly,and the richness of Proteobacteria,and Cyanobacteria decreased significantly in the S2 group.After the addition of 1000 mg/kg TB,the richness of Firmicutes were significantly decreased,Proteobacteria and Clostridium were significantly increased,and Firmicutes,and Proteobacteria were not significantly different from that of the S1 group.At the level of genus,the richness of Bacteroidetes,Erysipelatoclostridium,and Eubacterium were significantly increased in the S2 group,and Broutsiella,Escherichia-shigella,and aquatic bacteria were significantly decreased.After the addition of1000 mg/kg TB,the richness of Acinetobacter,Erysipelatoclostridium,and Eubacterium were significantly decreased,and Alkalibacterium was significantly increased.4.The regulatory effect of TB on the immune stress process of juvenile grass carps after LPS stimulationThe WGR of grass carps in the T600 and T1000 groups were significantly increased compared with the T0 group.After intraperitoneal injection of LPS,serum C3,C4 and IgM,AKP,GLU,SOD and liver GOT and GPT activities in the T0 and T1000 groups were rise first and then fall,but in a certain period of time T1000 group of C3,C4 and IgM,GLU,SOD,GOT and GPT activities were significantly higher than that of T0 group,MDA content increase softer,and below the T0 group.In summary,the feed with the higher cottonseed and rapeseed meal concentration has negative effects on the growth performance,immune system and intestinal health of grass carp.However,the addition of TB can promote the growth and the immune function,optimize the intestinal tissue structure and microflora structure of grass carps.Under the experimental conditions,the optimal TB supplementation was estimated to be 600-1000mg/kg diet.