Effects Of Comfrey Polysaccharides On Production Performance And Cecal Microflora Of Laying Hens

Comfrey(Symphytum officinale L.)is a forage and medicinal plant of the Boraginaceae,containing polysaccharides,triterpenes,phenolic acids,allantoin,and other active substances.At present,the preparation and physicochemical properties of comfrey polysaccharides(CPs)have been reported.However,there is no research on the of effects of CPs on performance of laying hens.The digestion and fermentation dynamics of CPs in vitro were studied in this research to lay a foundation for animal experiments.CPs were added to the diet of high-yielding laying hens to study its effects on the production performance,egg quality,and cecal microflora of laying hens.The purpose of this study was to provide scientific research for the development and utilization of comfrey resources and the development of natural polysaccharide feed additives in laying hen production.A total of 300 Hy-Line Brown laying hens were divided into 5 groups with 6replicates per group and 10 hens per replicate.The laying hens were fed diets containing CPs at levels of 0%(CK),0.5%(CPL),1.0%(CPM),and 1.5%(CPL),respectively.Inulin(IN)at 1.5% was used as a positive control.The experiment lasted for 42 days.The measured indicators included laying hen production performance,egg quality,nutrient metabolic rate,cecal short chain fatty acids(SCFAs),cecal microflora,and cecal content metabolomics.In vitro digestion experiment showed that CPs could hardly be digested by simulated digestive juices.In the in vitro fermentation test,CPs could be utilized by chicken cecum microflora.CPs could reduce the p H and increase the production of SCFAs in the fermentation broth.At the genus level,CPs increased the relative abundance of Lactobacillus.Dietary supplementation with CPs at the level of 1.0% and IN could increase the egg production rate of laying hens.CPs had no significant effect on egg quality.CPs(0.5% and 1.0%)increased the crude fat metabolism rate of laying hens.The contens of total protein(TP)and glucose(GLU)in serum were enhanced in the supplementation groups of CPs.The total antioxidant capacity(T-AOC),glutathione peroxidase(GSH-Px)activity,and superoxide dismutase(SOD)activity in serum and eggs were increased by CPs.The contents of malondialdehyde(MDA)in serum and eggs were reduced by CPs.These results indicated that CPs could improve the production performance and antioxidant capacities of laying hens.Dietary supplementation with CPs at the level of 1.0% and 1.5% CPs significantly decreased the p H and increased the concentrations of total SCFAs,acetic acid,and butyric acid in the cecal contents of laying hens.16 S r DNA sequencing showed that CPs significantly increased the richness and diversity of cecal microbial communities.At the phylum level,1.0% and 1.5% CPs significantly increased the relative abundance of beneficial bacteria Bacteroidetes and decreased the relative abundance of Fusobacterium.At the genus level,1.0% and 1.5% CPs significantly increased the relative abundance of the beneficial bacterium Ruminococcus and decreased the relative abundance of the harmful bacterium Fusobacterium.Environmental factor association analysis showed that Ruminococcus was positively correlated with butyrate.In order to further study the effects of CPs on cecum microflora,metagenomic and metabolomic analyses of cecum contents of laying hens supplemented with 1.0% CPs were carried out combined with the performance measurement results.Metagenomic analysis showed that CPs increased the relative abundance of the beneficial bacteria Bacteroidetes and decreased the relative abundance of the harmful bacteria Proteobacteria at the phylum level.At the family level,CPs significantly increased the relative abundance of the beneficial bacteria Prevotella and Ruminococcus,and decreased the relative abundance of the harmful bacteria Fusobacterium.At the genus level,CPs significantly increased the relative abundance of Ruminococcus.These results indicated that the intake of CPs could promote the proliferation of probiotics in the intestine of laying hens,inhibit the production of harmful bacteria,and have a positive effect on the intestinal health of laying hens,thus improving the production performance.KEGG enrichment analysis showed that CPs up-regulated metabolic pathways such as carbohydrate metabolism,purine metabolism,pyrimidine metabolism,and amino acid metabolism.Metabolomic analysis showed that CPs increased metabolites such as glutamate and cholic acid in the cecum of laying hens.Metagenomics and metabolomics association analysis showed that Ruminococcus was positively correlated with butyric acid.Prevotella was positively correlated with L-glutamic acid,D-fructose6-phosphate,etc.The KEGG metabolic pathway showed that CPs significantly up-regulated pathways such as amino acid metabolism,purine metabolism,and pyrimidine metabolism.In conclusion,the addition of CPs to the diet of laying hens could improve production performance and antioxidant capacities.CPs could increase the contents of SCFAs,reduce the p H value,and improve the richness and diversity of cecal microflora in the cecum of laying hens.CPs could promote the growth of beneficial bacteria,inhibit the production of harmful bacteria,and improve metabolic pathways such as amino acids.This research had guiding significance for the development of comfrey and its application in the production of laying hens.