Influence of Saccharomyces cerevisiae CNCM I-1077 on the fecal pH, markers of gut permeability, fecal microbiota, and markers of systemic inflammation in sedentary horses fed a high-starch diet.

Thirty mature Quarter Horse geldings were used in a completely randomized 32-d study to test the hypotheses that supplemental live Saccharomyces cerevisiaeCNCM; I-1077 improves apparent digestion, stabilizes the fecal pH, reduces gut permeability, maintains microbial communities, and decreases inflammation in horses fed a high-starch diet. Horses were stratified by body weight (BW), age, and body condition score (BCS) to one of two treatments: concentrate formulated with 2 g starch · kg BW-1 · meal-1 (control (CON); n = 15) or the same concentrate top-dressed with 25 g/d S. cerevisiae CNCM I-1077 (treatment (SC); n = 15; 8 × 108CFU). Horses were fed individually in stalls every 12 h. Between meals, horses were housed in dry lots with ad libitum access to water and Coastal bermudagrass hay. On days 0 and 32, BW and BCS were recorded, and blood was collected before feeding and 2, 8, 16, and 24 h postmeal on day 32 to analyze serum D-lactate. Fecal samples were collected on days 0, 16, and 32 at 8, 16, and 24 h postmeal for fecal pH and starch content. Intake and fecal production were recorded over 4 d to measure digestibility on days 28-31. Whole blood total bacterial counts and 16S fecal microbiota rRNA sequencing were performed at days 0, 16, and 32. Results revealed an increased ∆BW in SC horses compared with CON horses (P = 0.03), with no change in BCS (P = 0.97). D-lactate tended to be greater in SC horses on day 32 at 16 and 24 h postmeal compared with CON horses (P = 0.10). Concentrations of TNFα and LogCCL2 decreased from day 0 to day 32 regardless of dietary supplementation (P ≤ 0.02). Fold change of percent reads from day 0 in whole blood bacterial 16S rRNA did not differ between groups. Fecal starch was undetectable, and there were no differences in intake or apparent digestibility. Fecal pH tended (P = 0.07) to be lower in CON at 0 h on day 32 (6.03 ± 0.06) than on day 16 (6.14 ± 0.06). Additionally, pH tended (P = 0.09) to be lower in CON (6.03 ± 0.06) than in SC (6.16 ± 0.06) at 0 h on day 32. Supplementation of S. cerevisiae CNCM I-1077 maintained Bacteroidales and reduced acidosis-like bacteria like Streptococcus and potential pathogens like Enterobacteriaceae, Stenotrophomonas, and Rhodococcus at day 16 (P < 0.05). Furthermore, supplementation increased fibrolytic bacteria at day 32, such as Ruminococcus, Fibrobacter, and Succinivibrio (P < 0.05). These results indicate S. cerevisiae CNCM I-1077 increases BW and promotes a more diverse microbiome when horses are fed ad libitum hay and a high-starch concentrate.