Prevention And Treatment Effect And Mechanism Of Yeasts On Subacute Ruminal Acidosis In Sheep

Subacute ruminal acidosis(SARA)is a common nutritional and metabolic disease of ruminants.In ruminant breeding,a large number of high concentrate diets are often fed to achieve maximum production performance.The fermentation of high concentrate diets in rumen leads to the accumulation of acidic organic matter.The ruminal p H is at a low level for a long time,which causes SARA and brings substantial economic losses to animal production.Studies have confirmed that feeding yeast effectively alleviated the SARA.Still,yeast strains in existing probiotics are mainly separated from the outside,which is difficult to colonize and grow in the rumen,resulting in dangerous effects in the application.In order to obtain a yeast strain with a better control effect on SARA,three strains of rumen-derived yeast(Pichia manshurica N04,Diutina rugosa N09,and Diutina rugosa N07)and Saccharomyces cerevisiae ACCC 21162 were used as experimental materials in this study.SARA was induced in sheep by gradually increasing the feed concentrate-to-roughage ratio.The four yeast cultures were fed to the sheep in SARA induction,the sheep with SARA and the fattening sheep with reasonable diets,respectively.Clinical manifestations were observed and recorded daily.Lactic acid,histamine and endotoxin in rumen fluid and serum were determined.Blood gas analysis and serum biochemical indicators were measured.The production performance was determined.The 16 S r RNA sequencing and bioinformatics methods were used to analyze the rumen microflora.Our study explored the control effects and mechanisms of four yeast strains on sheep SARA and provided excellent strains and theoretical basis for the development of probiotics to control ruminant SARA.The results show that:1.During the induction of SARA in sheep,the p H in rumen fluid,actual bicarbonate and total carbon dioxide in the blood,and whole blood base excess of the yeast groups were significantly higher than those of the SARA induction group(P < 0.05).The histamine in rumen fluid,serum lactic acid,and blood anion gap were significantly lower in the yeast groups than those of the SARA induction group(P < 0.05).There were no significant differences in oxygen partial pressure,total carbon dioxide,actual bicarbonate,anion gap,and whole blood base excess in the blood between the yeast groups and the control group(P ≥ 0.05).The histamine in rumen fluid of the Diutina rugosa N07 group was significantly lower than that of the Saccharomyces cerevisiae group(P < 0.05).Blood oxygen partial pressure of the Diutina rugosa N07 group and the Diutina rugosa N09 group were significantly lower than those of the Saccharomyces cerevisiae group(P < 0.05).Among the yeast groups,the Diutina rugosa N07 group had the lowest serum histamine and the highest blood bicarbonate and whole blood base excess.2.During the treatment of SARA in sheep,the p H in rumen fluid,total carbon dioxide and actual bicarbonate in the blood of the yeast groups were significantly higher than those of the SARA model group(P < 0.05).The histamine in rumen fluid and the anion gap in the blood of the yeast groups were significantly lower than those of the SARA model group(P < 0.05).There were no significant differences in oxygen partial pressure,total carbon dioxide,actual bicarbonate and anion gap in the blood,serum lactic acid and histamine between the yeast groups and the control group(P ≥ 0.05).The lactic acid in the rumen fluid of the Diutina rugosa N07 group was significantly lower than that of the Saccharomyces cerevisiae group(P < 0.05).The whole blood base excess of the Diutina rugosa N07 group was significantly higher than that of the Diutina rugosa N09 group(P < 0.05).Among the yeast groups,the Diutina rugosa N07 group had the lowest histamine and the highest p H in rumen fluid.3.Saccharomyces cerevisiae ACCC 21162 and two Diutina rugosa strains were selected to determine the effects of the control process on rumen microflora.The rumen microflora richness increased.During the induction process,the most bacteria of the Saccharomyces cerevisiae group was Lactobacillus,the most bacteria of the Diutina rugosa N09 group was Pseudoscardovia,and the most bacteria of the other groups was unidentified Prevotellaceae.The relative abundance of Lactobacillus in the Saccharomyces cerevisiae group increased significantly(P < 0.05),and the relative abundance of Megasphaera in the Diutina rugosa N09 group increased significantly(P < 0.05).The enrichment of metabolic genes of the Diutina rugosa N07 group was similar to that of the control group.During the treatment process,the most bacteria of the Saccharomyces cerevisiae group was Lactobacillus,and the most bacteria of the two Diutina rugosa groups was unidentified Ruminococcaceae.The relative abundance of Mogibacterium in the Diutina rugosa N09 group increased significantly(P < 0.05).The enrichment of metabolic genes was similar between the Saccharomyces cerevisiae group and the control group.4.After 50 days of adding yeast cultures to sheep in the fattening period,the lactic acid in the rumen and blood sugar of the yeast groups was significantly lower than that of the control group(P < 0.05).The serum aspartate transaminase of the Saccharomyces cerevisiae group and Diutina rugosa N09 group was significantly lower than that of the control group(P < 0.05).The differences of endotoxin and histamine in rumen fluid,p H,oxygen partial pressure,actual bicarbonate and anion gap in the blood,histamine,endotoxin,alanine transaminase,urea nitrogen,total bilirubin,direct bilirubin,indirect bilirubin,total protein,albumin and globulin in the serum of the yeast groups with those of the control group were not significant(P ≥ 0.05).The p H of rumen fluid in the Saccharomyces cerevisiae group and the Pichia manshurica group was significantly higher than that in the control group(P < 0.05).All indicators were within the normal range.Our study showed that Diutina rugosa N07 had advantages in reducing body inflammation,regulating rumen microflora,and maintaining body alkali reserve.The rumen-derived yeasts were preliminarily verified to be safe and reliable without toxic effects and side effects,and it could provide an excellent strain for ruminant SARA probiotics.