Effects And Correlation Of Subacute Rumen Acidosis On Oral Microflora In Dairy Goats

As a common issue in dairy animals,subacute rumen acidosis(SARA)is always accompanied by a disturbed rumen microbiota.Considering rumination,the communication of ruminal and oral microbiota could be affected by SARA.Therefore,determining the association between oral microbiota and SARA may provide new insights for diagnosing SARA.To study the effects of SARA on rumen and oral microbiota,two high-concentrate diets with gradually increasing rumen-degradable-starch(RDS)were designed to induce SARA in dairy goats.The 16 S rRNA sequencing technology was applied to analyze the microbial composition of the rumen and oral cavity,and transcriptome was used to profile the immune function of the rumen epithelium.In addition,machine learning algorithms,such as random forest and support vector machine(SVM)analyses,were used to explore the relationship between rumen and oral microorganisms during SARA.Experiment 1 The effect of subacute rumen acidosis on rumen microbiota and rumen epithelium in dairy goatsForty-seven healthy dairy goats with ruminal fistulas and an similar body condition of(40 ± 4 kg,2-3 y)were used in this experiment.When fed with the 2 different high-concentrate diets,the goats exhibited the SARA occurrence or healthy(SARA tolerance)condition by continuous identification of ruminal pH alteration,which separately named as low-rumen-degradable-starch tolerance(LRDST),low-rumen-degradable-starch SARA(LRDSS),high-rumen-degradable-starch tolerance(HRDST),and high-rumen-degradable-starch SARA(HRDSS)groups.Then their ruminal microbiome and epithelial transcriptome were compared with the control(CON)group goats that fed with low concentrate diets,with aims to identify the effect of SARA on rumen microbiota and rumen epithelium.There was no significant difference in the α-diversity of ruminal bacteria among the 5 groups(P > 0.05),while the β-diversity varied(P < 0.05).Compared with the CON group,Ruminococcus,norank＿f＿norank＿o＿RF39 and Succinivibrionaceae＿UCG-002 significantly increased both in the LRDSS and HRDSS groups,and Prevotellaceae＿UCG-003,unclassified＿f＿Rikenellaceae,Lactobacillus,Marvinbryantia and Lachnospiraceae＿FE2018＿group significantly decreased both in the LRDSS and HRDSS groups(P < 0.05).Although some differences in ruminal bacteria were found between SARA and SARA tolerant dairy goats,regular changes were lacking.By SVM and random forest classification analyses,it was found that both ruminal Prevotellaceae＿UCG-003 could effectively distinguish SARA dairy goats from healthy dairy goats.Accroding to the functional composition profiles of rumen microorganisms predicted by PICRUSt2,SARA significantly enhanced the immune related pathways of rumen bacteria.The transcriptomic results showed that SARA significantly affected multiple immune-related pathways.Compared with the CON group,immune-related genes such as RSDA2,CCL20,MX1,DDX58,SIGLEC15,CPA3,and IRF7 were significantly up-regulated in the LRDSS group(P<0.05).Correlation analysis showed that Ruminococcus,Succinivibrionaceae＿UCG-002,norank＿f＿norank＿o＿RF39 and Tyzzerella were the main pro-inflammatory bacteria in the rumen.In addition,changes in the abundance of fiber-degrading bacteria in the oral cavity may reflect the health status of the rumen.Experiment 2 The effect of subacute rumen acidosis onoral microbiota in dairy goatsIn this study,oral(buccal mucosa and teeth)microbial samples were collected from dairy goats using sterile swabs at 2 h after morning feeding.Using 16 S r RNA gene amplicon sequencing and machine learning algorithms,we explored the differences in the composition of oral and rumen microbiota,and the relationship between oral and rumen microbes and rumen fermentation parameters under SARA.The α diversity of buccal mucosa microbiota was significantly higher than that of rumen microbiota(P < 0.01),and the α diversity of dental microbiota was significantly lower than that of rumen microorganisms(P < 0.001).In addition,there was a significant difference in β diversity among different sites(P = 0.001).Two microbial types,Streptococcus and Ruminococcus,were identified in the oral cavity and rumen,respectively.SARA significantly changes the composition of the oral microbiota,Prevotella,Prevotellaceae＿UCG-003,norank＿f＿Prevotellaceae,Lachnospiraceae＿AC2044＿group,Lachnospiraceae＿NK4A136＿group and other 14 genera in buccal mucosa decreased gradually along the CON group,the LRDSS group and the HRDSS group.SVM and random forest classification analysis showed that buccal Prevotellaceae＿UCG-003 was equally effective in identifying SARA and healthy dairy goats,suggesting that Prevotellaceae＿UCG-003 may be a potential biomarker for SARA.Source Tracker analyses suggested decreases of transmission between rumen and buccal microbiota in SARA dairy goats.The microbial networks showed the connections between microorganisms gradually decreased with the development of SARA in the rumen and buccal mucosa.Moreover,SARA was also found to have little effect on tooth microbiota.Overall,oral microbiota could be affected by the rumen.SARA will lead to dysbiosis of oral microbiota,that may be affected through the communication of ruminal and oral microbiota.Further,Prevotellaceae＿UCG-003 in rumen fluid and buccal mucosa could be a potential biomarker of SARA.Regular monitoring the change of oral microbiota may become effective strategies to diagnose SARA.