The use of enzyme mixtures, such as phytases with protease, xylanases and amylases has been on the rise. While the synergistic effect of these enzymes, if present, is not completely understood, their effects are complementary rather than substitutive as previously thought. A few years ago, many researchers reported that supplementing corn-soybean broiler starter diets with enzyme preparations containing a mixture of xylanase, protease and amylase resulted in improvements in BW but the effects were seldom significant on feed conversion ratio (FCR).