Effects Of Dietary Forage To Concentrate Ratio On Milk Performance,Blood Biochemical Indexes And Rumen Microflora In Dairy Goats

The dietary forage to concentrate ratio affects the lactation performance of ruminants,rumen microorganism play an important regulatory role in this process.But most of the microorganisms in the rumen cannot be cultured,and their function is not clear.Metagenomics provides an effective method for studying structure and function of rumen microflora.Therefore,the objective of this study is to investigate the effect of different ratio(50:50;30:70)of forage to concentrate on milk performance and blood biochemical indexes.Metagenomics was used to analyze the differences in the structure and function of rumen microflora in two groups,in order to provide a reference for the dietary regulating milk performance in dairy goats.In this study,eighteen(110±3d days)Xinong Saanen dairy goats with the similar age and parity were randomly divided into two groups,and nine dairy goats in each group were divided into three stalls,with each stall have three goats,which were fed with the ration F50(concentrate to forage = 50: 50)or F70(concentrate to forage = 30: 70),respectively.All goats were fed for 12 weeks.Milk performance and rumen microflora of dairy goats were determined,and the results were as follows:1.Effect of dietary forage to concentrate ratio on milk performance in dairy goatsCompared to F50,F70 increased the milk fat content significantly(P<0.05),and increased the milk fat content by 17.2%.Although DMI was reduced(P<0.05)for goat with F70,milk yield,milk component yield,milk protein and lactose content were not affected in two groups(P>0.05).2.Effect of dietary forage to concentrate ratio on blood biochemical indexes in dairy goatsThe ratio of concentrate to forage did not affect the contents of blood TP,GLB,TC,TG,Ca,BUN,GLU,ALB,and A/G(P>0.05)in dairy goats,suggesting that the two rations provided to the animals in present study could meet the basic nutrition requirements of dairy goats and do not affect body metabolism.3.Effect of dietary forage to concentrate ratio on structure of rumen microflora in dairy goatsThe results of metagenome sequencing showed that the dominant microbial communities in rumen microflora of the two groups were Bacteroides,Scleroderma,Archaea and Proteobacteria.The dominant genera at the genus level was Prevost’s bacteria,while the secondary dominant genera were Bacteroides,Cladosporium,Brevibacterium methanolicum,Clostridium,Montomonas,Vibrio butyricum,unclassified＿p＿Firmicutes,and unclassified＿f＿Lachnospiraceae.In addition,each of the two groups had its own secondary dominant bacteria.There was no significant difference on microorganism at phylum level between two groups.Compared to F50,the relative abundance of unclassified＿o＿Bacteroidales of F70 decreased significantly(P<0.05).4.Effect of dietary forage to concentrate ratio on function of rumen microflora in dairy goatsThe KEGG function prediction showed that the ratio of concentrate to forage did not affect the dominant position of carbohydrate and amino acid metabolism.However,Compared to F50,F70 increased the gene abundance involved in Glycan biosynthesis and metabolism and Biosynthesis of other secondary metabolites pathway in rumen microbiota and reduce the gene abundance involved in immune system pathway(P<0.05).The CAZy function prediction showed that increasing the proportion of forage would significantly increase the gene abundance of GH families such as GH95,GH51,GH43,GH5＿2 and GH134 and PL families like PL6＿3(P<0.05),reduce gene abundance of PL15＿1 of PL family and CBM12 with active region of chitin-binding protein(P<0.05).To sum up,under the conditions of this experiment,increasing the proportion of forage in diet decreased the DMI and increased the milk fat content by 17.2% with unaffected milk yield and blood biochemical indexes,indicating improved milk performance of dairy goats.The mechanism of dietary forage to concentrate ratio in ration affects milk performance of dairy goats was as follows: ratio of concentrate to forage in ration did not change the dominant position and relative abundance of the dominant microbial communities in the rumen microflora,which provided a stable rumen environment for the degradation of feed nutrients in the rumen.Increase of forage proportion in diet enhanced the ability of immunity and the use of the active ingredients and fiber material in plant sources of feed of dairy goats,reducing the abundance of gene related to rumen microbial resistance and pathogenicity and improving the abundance of gene related to Glycan biosynthesis and metabolism and Biosynthesis of other secondary metabolites and the gene abundance related GH families.