Mechanism Of The Fermented Aerial Part Of Bupleuri On Lipid Metabolism Of Liver On Laying Hens

The disorder of liver lipid metabolism leads to the fatty liver hemorrhagic syndrome(FLHS)in laying hens.FLHS decreases egg production and increases non-infectious mortality rate in caged laying hens,causing significant economic losses in the layer industry.Regulating liver lipid metabolism and protecting liver health of laying hens are of great significance for layer industry.Bupleuri,a kind of herb,is used to treat the fatty liver.Aerial part of Bupleuri,the by-product in the progress of Bupleuri planting,has some saponins and flavones.The high cellulose and wrong palatability restrict the application of aerial part of Bupleuri in feed on laying hens.In our study,fermented aerial part of bupleuri fed to laying hens to explore the effects on lipid metabolism in laying hens.We established a model of fatty liver via high energy and low protein diet in laying hens and fed with Saikosaponin a(SSa)to explore the mechanism of FAPB on regulating hepatic lipid metabolism of laying hens by using 16S r DNA high-throughput sequencing and bile acid targeting metabolomics technology.This study provided theoretical foundation for the application of FAPB.The main research contents and results are as follows:Exp.1 Different levels of FAPB affect the lipid metabolism on laying hensComplex probiotics(Bacillus:2×10~9CFU/g,Lactobacillus:3×10~9CFU/g,Saccharomycetes:5×10~8CFU/g)was used as microbial strain for FAPB and corn-soybean meal was used as energy.FAPB made by anaerobic fermentation in fermentation cylinder.A total of 384 35-week-old laying hens were randomly allocated into 4 treatments with 8replicates(12 birds per replicate).They were fed with a basal diet and three levels FAPB diet(including 5%,10%,15%FAPB).The test period was 14 weeks,of which the pretest period was 2 weeks,and the experiment period was 12 weeks.At the end of the period,liver and serum was collected to measure the indexes of lipid metabolism.The results showed that:The 10%and 15%FAPB diets significantly reduced the organ index of liver compared with the basal diet group;all FAPB diets decreased the level of cholesterol in serum and yolk.FAPB improved the laying hen lipid metabolism by decreasing the cholesterol accumulation in laying hens and egg.The expression of liver genes results showed that all FAPB diets decreased the expression of SREBP-1.15%FAPB diet increased the expression of HMGCR,SREBP-2,PPARγ,LXRα,APO-VLDL,CYP7a1.FAPB decreased the accumulation of lipid on laying hens.15%FAPB diet was the optimum diet.Exp.2 The effect of SSa on the lipid metabolism of laying hensSSa,the primary bioactive ingredient in Radix Bupleuri,alleviated the fatty liver by regulating hepatic lipid metabolism.The experiment 2 aimed to explore the effect of SSa in FAPB on lipid metabolism of laying hens.A total of 54 35-week-old laying hens were randomly allocated into 3 treatments with 6 replicates(3 birds per replicate).They were fed with a basal diet,a high-energy and low-protein diet,or a high-energy and low-protein diet with SSa(30 mg/kg).Our study revealed that SSa treatment significantly reduced diet-induced abnormal lipid metabolism,particularly the accumulation of abdominal fat,liver cholesterol and yolk cholesterol.Histopathology results showed that SSa reduced the diet-induced hepatic cell lipid deposition.Serum measure result showed that SSa relieved the diet-induced liver cell injury.The expression of liver genes involved in cholestrol metabolism like CYP7a1,LXRα,and PPARαwas increasing,but SREBP1 expression was decreased.SSa decreased the hepatic lipid accumulation and alleviated the diet-induced liver injury by regulating bile acid synthesis.Exp.3 The regulation of SSa on intestinal flora and bile acids in the ileum of laying hensThe experiment design is the same as experiment two.At the end of period of experiment,ileal content was collected to measure the gut microbiota and bile acid.The diet challenge affected theβ-diversity,but notα-diversity.SSa decreased the relative abundance of Firmicutes and increased the Actinobacteria.SSa decreased BSH-producing genus such as Lactobacillus,Bifidobacterium and Turicibacter.Ileal BA metabolomics analysis indicated that SSa enhanced the content of tauro-conjugated BAs,principally Taurochenodeoxycholic acid and Tauro-α-Muricholic acid.SSa inhibited the expression of ileal FXR,FGF19,and ASBT,indicating that SSa decreased the reabsorption of BA in ileum and promoted the metabolism of cholesterol in liver.In conclusion,FAPB decreased the lipid accumulation on laying hens and 15%FAPB was useful.SSa relieved diet-induced liver cholesterol accumulation by decreasing the abundance of BSH-produced intestinal flora and altering ileum BAs content,thereby suggesting that SSa may be used to provide viable treatment for fatty liver in laying hens.