Effect Of Active Dry Yeast And Yeast Culture On Performance And Mechanism Of Dairy Cows

The aim of this experiment was to investigate the effect of adding active dry yeast(ADY)and yeast culture(YC)to the diet on the production performance,apparent digestibility,and rumen fermentation parameters of lactating dairy cows,and to explore the effect of adding active dry yeast and yeast culture to the diet on rumen microorganisms at the macro-genomic level using high-throughput sequencing technology.And the changes in rumen metabolites following the addition of active dry yeast and yeast culture were studied at the metabolomic level to explore the association between rumen microorganisms and metabolites,with a view to investigating the effects of active dry yeast and yeast culture on dairy cows and their mechanisms of action.Seventy-five Chinese Holstein cows with similar days in milk,parity and average daily milk yield were randomly divided into three groups,which were control group(CON group),live yeast group(ADY group)and yeast culture group(YC group),with 25 replicates of each group.The cows of CON group were fed a total mixed ration,while the ADY group were additionally fed 20 g/d/head active dry yeast on the basic of total mixed ration and the YC group were additionally fed 30 g/d/head of yeast culture on the basic of total mixed ration.The results showed that: 1)the addition of active dry yeast and yeast culture to the diet had no significant effect(P>0.05)on milk fat percentage,milk fat-protein ratio,milk lactose percentage,total milk solids,somatic cell count and urea nitrogen concentration,but tended to increase dry matter intake(P=0.082),milk yield(P=0.062)and milk protein percentage(P=0.091);the addition of yeast preparation to the diet had no significant effect on the apparent digestibility of ether extract,neutral detergent fiber and acid detergent fiber(P>0.05),but increase the apparent digestibility of crude protein(P=0.05),and reduced the ORP of the group YC significantly(P<0.05);the addition of active dry yeast and yeast culture had a tendency to increase the concentration of the total volatile fatty acid(P=0.098),but the p H,concentration of microbial protein,acetic acid,propionic acid,butyric acid,and acetic acid/propionic acid have no significant Impact(P>0.05).2)Metagenomic results showed that dietary yeast preparation had no significant effects on rumen microbial species composition,GO functional genes,KEGG metabolic pathway and active carbohydrate enzymes.The metabolome test showed that the top 10 metabolites with the largest difference multiple changes were significantly up-regulated in the active dry yeast group compared with the control group,methylmalonic acid(Methylmalonic acid),prostaglandin D3(Prostaglandin D3)and pyrophosphate(Pyrophosphate)were the top three metabolites with the largest up-regulated.Compared with the control group,only 4-pyridoxicacid was significantly upregulated in the top 10 metabolites with the largest difference multiple changes in the yeast culture group.The active dry yeast group vs the yeast culture group,the difference metabolites were mainly significantly enriched in 3 pathways,and the top 10 differential metabolites with the largest change in the difference multiple were all significantly up-regulated,and the two metabolites with the largest up-regulated range were D-xylose(D-Xylose)and Glyceric acid(Glyceric acid).The main enrichment pathways of these differential metabolites are amino acid metabolism and lipid metabolism,suggesting that yeast preparation may perform function by affecting the metabolites involved in these pathways.3)The results of plasma metabolomics showed that,compared with the control group,arginine,serine and phenylalanine(Arg Ser Phe)were the most up-regulated metabolites in the living yeast group,while sphinganine(Sphinganine)was the most downregulated metabolite.The differential metabolites were mainly concentrated in aminoacylt RNA biosynthesis(Aminoacyl-t RNA biosynthesis)and sphingolipidabolism(Sphingolipid metabolism)pathways.Compared with the control group,arginine,serine and phenylalanine(Arg Ser Phe)were the most up-regulated metabolites in the yeast culture group,while sphinganine(Sphinganine)was the most down-regulated metabolite.The differential metabolites tended to be mainly concentrated in aminoacyl-t RNA biosynthesis(Aminoacylt RNA biosynthesis)pathway(P=0.054).Compared with the active dry yeast group,4-hydroxyphenylpyruvic acid(4-Hydroxyphenylpyruvic acid)and 2-aminobenzoic acid(2-Aminobenzoic acid)of the difference metabolites were upregulated,2,6-dihydroxybenzoicacid(2,6-Dihydroxybenzoic acid)and alpha-linolenicacid(AlphaLinolenic acid)were significantly down-regulated,and the differential metabolites were mainly concentrated in Histidine metabolism pathway.In summary,the addition of active dry yeast and yeast culture tend to increase supplement can increase the dry matter intake,milk yield,milk protein percentage,the concentration of the total volatile fatty acid and significantly increase apparent digestibility of crude protein of cows,the addition of yeast culture significantly reduce the ORP in the rumen.In addition,the active dry yeast and yeast culture had no significant effect on the level of microbial metagenome in the dairy cows,and the metabolites were mainly concentrated in the pathways of amino acid metabolism,lipid metabolism and vitamin metabolism.However,active dry yeast and yeast culture supplementation in diet could significantly affect the levels of plasma metabolites,and the difference of metabolites was mainly concentrated in the amino acid metabolism and lipid metabolism pathways.Therefore,active dry yeast and yeast culture may perform function by affecting metabolites involved in amino acid metabolism and lipid metabolism.