Grinding cereal grains for cattle feeding is generally considered to be important for efficient digestion and to minimize waste. Maize could be an exception as whole maize (WM) is commonly used in lot—fed cattle when the diet contains less than 20% roughage (NRC 1996) and can be used to supplement grazing animals (Beretta et al. 2001). Mastication of grain during eating will probably play a major role in reducing particle size, given the bigger size of maize with respect to other grains. However, grinding maize can modify the site of starch digestion increasing rumen degradability without necessarily increasing the grain whole tract apparent digestibility.