Impact of Saccharomyces cerevisiae fermentation product and subacute ruminal acidosis on production, inflammation, and fermentation in the rumen and hindgut of dairy cows

The effects of a Saccharomyces cerevisiae fermentation product (SCFP) on microbial fermentation in the digestive tract, milk production, and inflammation response were determined in Holstein dairy cows under normal and subacute ruminal acidosis (SARA) conditions. Eight lactating dairy cows with ruminal and cecal cannulas were used in a cross-over design with 5 wk experimental periods. During the first experimental period, cows were randomly assigned to treatment, i.e. SCFP (Original XPC, Diamond V, Cedar Rapids, IA) or control. During the second experimental period, treatments were reversed. Experimental periods were separated by a two-week wash out period. During each period, the 4 cows on the SCFP treatment were supplemented with 14 g/d of SCFP in 126 g of ground corn, whereas the other four cows received 140 g ground corn only. During the first 4 wk of each experimental period, all cows received a basal diet. During week 5 of both experimental periods, a SARA challenge was conducted in all cows by replacing 208 g/kg of the basal diet with pellets of ground wheat and barley (50:50 on a weight basis). This SARA challenge increased the duration of rumen pH below 5.6 from 11.1 to 311.1 min/d, indicating successful induction of SARA. Inducing SARA reduced milk fat from 3.24 to 2.82%, and lowered the acetate to propionate ratio from 3.07 to 1.74 in rumen fluid, from 5.13 to 4.57 in cecal digesta, and from 4.81 to 4.34 in feces. Induction of SARA increased milk protein content from 3.23 to 3.32%, without a concomitant effect on milk protein yield. Inducing SARA also increased endotoxic lipopolysaccharide (LPS) in rumen fluid, cecal digesta and feces from 15,389 to 123,296 endotoxin units (EU)/mL, from 31,982 to 77,380 EU/mL, and from 29,679 to 77, 371 EU/mL, respectively. Concentrations of LPS, serum amyloid A, haptoglobin, and LPS-binding protein increased by 215.0, 250.6, 181.6 and 47.5%, respectively, in peripheral blood when SARA was induced. The SCFP did not affect feed intake, yields of milk, milk fat, and milk protein but it reduced the variation in rumen pH during control feeding. During the SARA challenge, SCFP tended to reduce ruminal LPS at 6 h after feed delivery, increased milk fat percentage (2.71 vs 2.92%, control vs SCFP), and reduced the extent of SARA-associated inflammation response as indicated by a reduction in the concentration of the pro-inflammatory cytokine tumor necrosis factor α (0.09 vs 0.03 ng/mL, control vs SCFP). This shows that SCFP can attenuate some of the impact of SARA on production and health of dairy cows.