This study aimed to evaluate the use of sodium monensina (Rumensin®) and yeast culture (Saccharomyces cerevisiae - Beef - sacc®) on concentration of short chain fatty acids (SCFA), ammonia and ruminal pH, and microbial efficiency in bubaline and bovine, fed diets with 50% concentrate. Three buffalos and three bovines whith cannulas on the rumen and duodenum were distributed in two Latin squares, with factorial arrangement 3 x 2. The concentrations of SCFA, ammonia and ruminal pH were determined every two hours. The flow of the digest and microbial protein on duodenum were determined from de utilization of insoluble ashes in acid and the utilization of purine bases as microbial indicator, respectively. The additives and species did not influence the total concentration of SCFA, acetic acids, propionic and butyric, but the addiction of yeast culture reduced the acetate/propionate ratio and the monensin reduced on a more effective and similar for the species, which were higher in the bubaline. The syntheses efficiency was higher in bovines, and reduced by the addiction of monensin. The yeast culture and monensin on ruminal fermentation changed in a positive way, and the cattle and buffaloes showed differences in the studied parameters.
short chain fatty acids; ammonia; ionophore; Saccharomyces cerevisiae