Effects of yeasts on rumen bacterial flora, abnormal metabolites, and blood gas in sheep with induced subacute ruminal acidosis

Abstract

This study was designed to evaluate the effects of one strain of Saccharomyces cerevisiae and two strains of rumen-derived Diutina rugosa on the ruminal microbial community, abnormal metabolites, and blood gas indexes in preventing subacute ruminal acidosis (SARA) in sheep. Therefore, this research aims to provide strains and a theoretical basis for developing probiotics to prevent SARA in sheep. A total of 50 Dorper sheep (♂) × Hu sheep (♀) F1 generations (20.50 ± 2.21 kg of body weight; 2 months old; half male, half female) were randomly divided into 5 groups with 10 sheep in each group: 1) SARA, increasing the ratio of concentrate-to-roughage gradually induced SARA; 2) SC, SARA +100 mL S. cerevisiae ACCC 21162; 3) DR1, SARA +100 mL D. rugosa N09; 4) DR2, SARA +100 mL D. rugosa N07; 5) CON, basal diet. Subacute ruminal acidosis occurred in sheep whose ruminal pH was between 5.2 and 5.6 for more than 3 h. After SARA, the rumen microflora, abnormal metabolites, and blood gas were measured. The results showed that SARA occurred in the SARA group with ruminal pH of 5.2–5.6 for more than 3 h, while SARA did not occured in other groups. Compared with the SARA group: 1) The richness indexes of rumen microflora increased in groups that were offered yeast. Additionally, the diversity indexes of rumen microflora increased in the D. rugosa groups. The relative abundance of rumen microflora changed, and the most prevalent bacteria in the SC, DR1 and DR2 groups were Lactobacillus, Pseudoscardovia, and unidentified Prevotellaceae. 2) Rumen lactic acid and serum endotoxin in the SC and DR2 groups decreased (P < 0.05), whereas rumen endotoxin in the DR1 group decreased (P < 0.05). Similarly, rumen and serum histamine and blood lactic acid decreased (P < 0.05) in groups that received yeast. 3) In groups that were offered yeast, blood pH, total carbon dioxide, bicarbonate concentration, and base excess increased (P < 0.05), while the blood anion gap decreased (P < 0.05). In conclusion, all three yeasts stabilized the ruminal pH, improved the richness of rumen microflora, relieved acidosis and inflammation, and prevented SARA in sheep. Moreover, the development of probiotics related to rumen yeasts shows potential probiotic effects.