Twenty Holstein dairy cows in early lactation were allocated equally to one of two treatments on the basis of age, days in milk, and mean daily 2-wk pretrial milk yield. All animals were fed a total mixed ration; the ration for the treatment group was top-dressed with 90 g/d of yeast culture, Saccharomyces cerevisiae. Treatment period lasted 10 wk. Mean daily DM intake, milk production, milk composition, and BW were not significantly affected by treatment. Feed and fecal samples were collected the last 3 d of the treatment period to determine apparent total tract nutrient digestibility using ADF insoluble ash as the inert marker. No significant differences in digestibility were observed between treatment groups for CP, ADF, and NDF.