In the last 3 decades, steers with elevated daily weight gains have been fed diets with a relatively high concentration of grain Laving high concentration of rapidly fermentable carbohydrates that reduce rumen pH, degradation of structural carbohydrates, feed intake, and productivity (Soto-Navarro et al. 2000). The effects of ruminal buffers (salt, weak acid, oxide or hydroxide) able to neutralize acids and reduce drastic changes of rumen pH (Staples and Lough 1989) were variable, mostly due to the wide variety of conditions in which these were tested (Erdman 1988). Rumen buffers seem to improve feed efficiency of ruminants fed diets with highgrain concentration (Kennelly et al. 1999). In the last decade, new ruminal buffers have emerged such as calcified-seaweed extracts (CSE). Therefore, the objective of this study was to evaluate the effects of CSE on ruminal disappearance and fermentation of steers fed diets with 30% forage and 70% concentrate
