Effects of supplementation with Saccharomyces boulardii CNCM I-1079 on the fecal microbiota of healthy young Japanese black calves: A field trial.

The effects of more than 1 month of supplementation with Saccharomyces boulardii on the gut microbiota of healthy young calves are unclear. The objective of this study was to describe the effects of 7 wk of supplementation with S. boulardii CNCM I-1079 on the fecal bacterial microbiota of healthy young Japanese black calves. Calves in the S. boulardii group (SB group) were fed 2.0 × 10¹⁰ CFUs/day of S. boulardii CNCM I-1079 in milk replacer starting at 2 wk of age. Fecal samples were collected and the V3 and V4 regions of 16S rRNA were sequenced. The SB group exhibited significantly higher fecal alpha diversity at 9 wk of age (7 wk after starting supplementation) than the untreated control group. Beta diversity differed at 6 and 9 wk of age (4 and 7 wk after supplementation). Analysis of the composition of microbiomes revealed that calves in the SB group had higher fecal levels of Bacilli_RF39 than the control group at 9 wk of age. Linear discriminant analysis of effect sizes revealed higher levels of Oscillospiraceae at 3 wk of age (1 wk after) and of Bacilli_RF39 and Atopobiaceae at 9 wk of age (7 wk after) in the SB group than in the control group. Furthermore, a higher abundance of bacteria-producing short-chain fatty acids (SCFAs) was observed at 9 wk of age than at 6 wk in the SB group. These findings indicate that S. boulardii CNCM I-1079 can increase bacterial alpha diversity and might increase the abundance of SCFA-producing bacteria in the gut of healthy young calves.