Diet Supplementation with Saccharomyces Cerevisiae Boulardii Improves Growth, Health, and Fecal Microbiota of Pre-Weaned Dairy Calves.

High morbidity and mortality rates of calves dramatically impact the sustainability of the dairy industry. Probiotics are investigated for their potential to alleviate health challenges. The objective of the study was to determine the effect of live yeast Saccharomyces cerevisiae var. boulardii CNCM I-1079 (SB) supplementation in pre-weaning calves. Thirty Holstein calves were enrolled at d6 of age and were offered daily 8 L of milk replacer with ad-libitum access to water and pelleted starter. Calves were balanced in term of parity of the dam and birth weight and randomly assigned to two experimental groups, designated as supplemented and Control. Supplemented calves received 2x109 cfu/d of SB added in the milk replacer. Every abnormal health condition, such as gut and respiratory disorders, as well as therapeutic treatments were recorded daily for each animal. A linear mixed model was performed to assess the impact of the supplementation on the different variables measured. Two fecal samples were collected at d10 and d60 of the trial to analyze bacteria diversity and taxonomic composition by amplicon sequencing. The overall health was improved in SB calves with fewer diarrhea cases detected compared with Controls (0.7 vs 2.2/calf, respectively, P = 0.001) and fewer SB calves experiencing respiratory disease (6.3 vs 50% respectively, P = 0.090). Along with those observations, a lower number of SB calves received a therapeutic treatment (18.8 vs 62.5% respectively, P = 0.029). Consequently, SB calves weighed 3 kg more compared with the Controls at the end of the experiment (P = 0.087). SB calves significantly presented a greater relative abundance of Akkermansia, a genus involved in immune system maturation, and a greater proportion of Lactobacillales and Negativicutes (lactate users) indicating likely better adaptation of their fecal microbiota to the milk diet than in Controls. [ABSTRACT FROM AUTHOR]