Meta-analysis of the effect of feeding live yeast (Saccharomyces cerevisiae) on feeding behaviour and lactation performance, rumen fermentation, and rumen microbiota in dairy cattle

The objective of this meta-analysis was to analyze the effect of feeding live yeast (Saccharomyces cerevisiae) on feed intake (FI), lactation performance (LP), rumen fermentation (RF), and rumen microbiota (RM) in dairy cattle. We performed a literature search using the Boolean search approach with MeSH keywords, including live yeast, Saccharomyces cerevisiae, S. cerevisiae, feed intake, lactation, performance traits, rumen, fermentation, microbiota, and cattle. Twenty-five (25) articles published contained at least data on feed intake, lactation performance or milk production parameters, rumen fermentation or digestibility, and rumen microbiota measured for experiments involving dairy animals have been selected. Microsoft Excel performed data extraction and organization, and statistical analysis was performed using SPSS. Few studies have observed a negative impact of the LY on the FI (8%), LP (12%), RF (4%), and RM (8%), but the majority of the selected studies reported a positive impact of adding LY (FI: 36%, LP: 52%, RF: 52% and RM: 40%). Cows supplemented with LY showed a marginal decrease in feeding rate; min/d (0.13 vs. 0.14; p=0.65), interval between meals; min (142.1 vs. 1603, p=0.09), meal size; kg of DM/meal (3.4 vs. 3.8, p=0.09), meal duration; min/meal (32.5 vs.35.3, p=0.39), lying boots; no/d (9.5 vs. 9.6, p=0.83), eating boot; bout/day (80.7 vs.8.26, p=0.24), and lying time; min/d (671.1 vs. 697.5, p=0.51). However, LY increases feeding duration; min/d (232.0 vs.226.6, p=0.65), meal frequency; meal/d (9.0 vs.7.8, p=0.07), rumination; min/d (570.3 vs. 344.9, 344.9, p=0.08), and meal criterion with significance; min (20.0 vs. 25.8, p=0.04). Meta-regression of the covariate effect shows that using live yeast products in the cattle diet significantly increased the Lactation Performance (p=.001) and Feed Intake (p=.001). However, it enabled a higher average ruminal Fermentation (p=.005) and microbiota (p=.003). Furthermore, the timing of live yeast culture before calving could influence the performance and ruminal parameters, especially the microbiomes (p=0.006). A little increase in milk yield (1.4kg/day) and lower SCS（somatic cells score (2.76) were observed in LY. This meta-analysis indicated feeding live yeast (Saccharomyces cerevisiae) could improve feeding behaviour, animal performance, and herd productivity (milk and rumen health). However, further research is required to study its effect on feed intake and rumen microbiota in dairy cattle.