Environmental efficiency of Saccharomyces cerevisiae on methane production in dairy and beef cattle via a meta-analysis.

The objective of the present study is to examine the effect of yeast (Saccharomyces cerevisiae) on reduction of methane (CH4 ) production in dairy and beef cattle using meta-analytic methods. After compilation of relevant scientific publications available from the literature between 1990 and 2016, and applying exclusion and inclusion criteria, meta-analyses of data from dairy and beef cattle were applied for the pooled dataset or for each animal category (dairy or beef). The results of meta-analysis of all three datasets (all cattle, dairy cattle, or beef cattle) suggested that effect size of yeast either on daily CH4 production or on CH4 production per dry matter intake (CH4 /DMI) was not significant. The results of Q test and I2 statistic suggest that there is no heterogeneity between different studies on CH4 production and CH4 /DMI. The results of meta-analysis suggest that use of yeast (Saccharomyces cerevisiae) as feed additive does not offer significant results in terms of reduction of CH4 production in dairy and beef cattle. Further research on the effects of different doses of yeast, use of yeast products, different strains, and experimental designs is warranted to elucidate the effects of yeasts on methane production in the rumen.