This study was conducted to evaluate the effects of live Saccharomyces cerevisiae yeast (LY) supplementation on high-starch diets for dairy cows. Using a 2 × 2 factorial design, four treatment groups were examined: adequate starch without LY (AS-control), AS with LY (AS-LY), high starch without LY (HS-control), and HS with LY (HS-LY). LY was added at 2.9 × 106 CFU/200 mg DM or without yeast. In vitro gas and methane (CH4) production, organic matter (OM) digestibility, rumen fermentation, and metabolizable energy (ME) were analyzed. The Hohenheim Gas Test apparatus was used, and total gas volumes were measured at various incubation hours. Results showed no significant effects of LY or dietary starch ratio on gas kinetics, total gas, or CH4 production. Similarly, OM digestibility, fermentation kinetics, and ME were unaffected. In conclusion, LY supplementation did not alter in vitro gas, CH4 production, OM digestibility, rumen fermentation, or ME. Further research could investigate the underlying mechanisms, such as rumen microbial population influences.
