Regulatory Effects Of Clostridium Butyricum On Intestinal Functions And Lipid Metabolism Of Laying Hens In The Late Phase Of Production

Three experiments were conducted to investigate the regulatory effects of Clostridium butyricum addition on intestinal functions and lipid metabolism of laying hens in the late phase of production.Exp.1 was aimed to probe the differential intestinal functionality of laying hens in the late phase and peak phase of production through RNA-Seq.Results showed that there were 104 up-regulated genes and 190 down-regulated genes in the ileum of layers in the late phase of production(60-wk-old)as compared with those at peak production(36-wk-old).The up-regulated genes were not enriched(Q>0.05)in any pathway,while the down-regulated genes were enriched(Q<0.05)in the pathways of PPAR signaling,oxidative phosphorylation and glutathione metabolism.GO analysis also found that these down-regulated genes were related to lipid metabolism,respiratory chain electron transport and antioxidant properties.In addition,the activities of total superoxide dismutase,glutathione S-transferase,Na+/K+-ATPase,total antioxidant capacity and ATP content were reduced(P<0.05)while malondialdehyde content was increased(P<0.05)in the ileum of layers in the late phase of production.These findings indicated that the ileum of layers in the late phase of production had disorders in lipid metabolism,energy generation and antioxidant capacity,providing targets for regulating intestinal functions in the late phase of production.Exp.2 was aimed at exploring the effects of C butyricum on intestinal functions and production performance of layers in the late phase of production.A total 384 Hy-Line brown layers in the late phase of production(60-wk-old)were divided into 4 groups(8 replicates).Birds were fed a basal diet supplemented with 0,0.3,0.9 and 2.7 g/kg C.butyricum(1.0×109 CFU/g).Samples were collected at the end of wk 8.Results showed that C.butyricum addition quadratically decreased(P<0.05)the feed-egg ratio during wk 5-8 and wk 1-8,and quadratically increased(P<0.05)yolk color.Addition of 0.9 g/kg C.butyricum increased(P<0.05)the total antioxidant capacity of ileum.Increasing C.butyricum addition quadratically lowered(P<0.05)ileal malondialdehyde content,quadratically increased(P<0.05)villus height,lipase activity,alkaline phosphatase and Na+/K+-ATPase activities and ATP content in the ileum,as well as quadratically increased(P<0.05)the mRNA expression of ileal L-type amino acid transporter 1 and fatty acid-binding protein 1.The above indexes were optimal(P<0.05)in 0.9 g/kg C.butyricum group,suggesting that supplemental 0.9 g/kg C.butyricum could improve intestinal absorption,antioxidant function and energy utilisation of layers in the late phase of production,thus conducing to the elevations of feed efficiency and yolk color.Exp.3 was conducted to explore the effect of C.butyricum on lipid metabolism of layers in the late phase of production and the related mechanisms.The experiment design was the same as Exp 2.Results showed that C.butyricum had a tendency to reduce serum triglyceride content(P<0.10),linearly increased(P<0.05)serum contents of glucagon-like peptide 1,insulin and thyroid hormones(T3 and T4),linearly decreased(P<0.05)the contents of hepatic triglyceride and free fatty acids,as well as linearly increased(P<0.05)the expression of liver fatty acid synthase,farnesoid X receptor(FXR),acyl-CoA oxidase and PPARa.These results suggested that adding high dose(2.7 g/kg)C.butyricum was beneficial for reducing lipid deposition in the liver of layers.Thereby,the samples from control and high dose C.butyricum groups were selected for further analysis.? diversity analysis showed a difference(P<0.05)in ileal microbial composition between control and treatment groups.C.butyricum addition increased(P<0.05)the abundance of Bacteroidetes and showed a trend to decrease the abundance of Firmicutes(P<0.10),which benefited the reduction of host lipid deposition.C.butyricum addition also increased(P<0.05)the abundance of Prevotellaceae and tended to increase the abundance of Bifidobacteriaceae(P<0.10),but decreased the abundances of harmful bacteria(Enterobacteriaceae(P<0.10)and Klebsiella(P<0.05),indicating that C.butyricum addition may alleviate the inflammatory state of layers and thus reduce the sensitivity of lipid deposition.Bile acids are important metabolites of gut microbiota to regulate host lipid metabolism.Results showed that C.butyricum addition reduced(P<0.05)the content of ileal tauro-a-muricholic acid,increased(P<0.05)the contents of ileal tauroursodeoxycholic acid and lithocholic acid,and tended to increase the content of glycochenodeoxycholic acid and hyodeoxycholic acid(P<0.10),as well as increased(P<0.05)the expression of ileal FXR,which could alleviate hepatic lipid accumulation through gut-liver axis.In conclusion,supplemental 0.9 g/kg C.butyricum(9×109 CFU/kg)could improve absorption and antioxidant function as well as energy utilisation of the intestine,probably contributing to the improvement of feed efficiency of layers in the late phase of production.Supplemental 2.7 g/kg C.butyricum(2.7×1010 CFU/kg)could accelerate hepatic fatty acid oxidation,as well as modulate gut microbial composition and their metabolite(bile acids)profile,thereby favoring the reduction of lipid deposition in the liver of laying hens in the late phase of production.