The study was designed to determine the effects of Diamond V Original XPC, a yeast fermentation product, in the diets of newly weaned beef steers on nutrient digestibility and response to a vaccination challenge. Although no overall performance benefit was noted, XPC improved total tract CP digestibility. Steers fed XPC at 14 g/d exhibited lesser concentrations of APP, greater DMI, and more efficient rumination post-vaccination. Further research is needed to determine the optimal supplementation rate of XPC to newly received beef cattle.