The effects of probiotics, yucca extract, monensin and L-cysteine on rumen methanogenesis were determined by in vitro incubation using mixed bovine rumen microorganisms with ground Bermuda grass hay as a substrate. Two forms of probiotics, yucca extract, monensin and L-cysteine were tested during 24 hour anaerobic incubations. Methane and carbon dioxide production and fermentation characteristi...