The objective of this study, conducted at the Southwest Regional Dairy Center, was to evaluate the effect of dietary supplementation of 2 different yeast culture concentrations on lactation performance of dairy cows. Multiparous crossbred cattle (n = 46) averaging 55 d in milk (DIM) at the start of a 14 d adaptation period were used in a randomized complete block design with a 42 d treatment period. Cows were balanced by parity, DIM, and milk yield (MY) and randomly assigned 1 of 3 dietary treatments: (1) Treatment A, 56 g of Cellerate Culture Classic (Phibro Animal Health Corp., Teaneck, NJ), plus a basal total mix ration (TMR) and 58 g of ground corn (A + TMR); (2) Treatment B, 14 g of a concentrated dried yeast product (not commercially sold; Phibro Animal Health Corp.) plus a basal TMR and 100 g of ground corn (B + TMR); and (3) Control (CON) consisting of a basal TMR plus 114 g of ground corn. Cows were housed in a free-stall barn equipped with a Calan Broadbent feeding system (American Calan, Inc., Northwood, NH) to allow for individual feedings daily. Milk yield and dry matter intake (DMI) were recorded daily and averaged/wk. Milk samples and TMR were collected for 3 consecutive d/wk and analyzed for components and DMI. The MIXED procedure of SAS (Cary, NC,) was used to evaluate fixed effects of period, treatment, and period × treatment with cow as random effect on MY (kg/d) and DMI (kg/d). Stepwise backward elimination was used to remove non-significant interactions (P ≥ 0.10). All main effects were kept in the model regardless of significance. No statistically significant differences (P ≥ 0.10) were observed for any of the 3 treatments on MY or DMI. Milk yield for A + TMR, B + TMR, and CON were, 43.76 ± 0.54, 43.09 ± 0.56, and 44.04 ± 0.55 kg/d, respectively. Dry matter intake for A + TMR, B + TMR, and CON 27.91 ± 0.47, 26.76 ± 0.48, and 27.98 ± 0.48 kg/d, respectively. This data suggests that supplementing cattle with 2 different concentrated yeast cultures shows no differences on MY and DMI.