Ninety-six multiparous early lactation (66 ± 23 DIM) Holstein cows were used in a randomized complete block design with 2 treatments, control (C) and additive (AD). Cows were blocked by DIM and milk yield then divided between 12 pens. Cows were fed a TMR 1 time daily with pens on the AD treatment being offered a direct-fed microbial blend (PMI Nutritional Additives, Shoreview, MN) and cows on the C treatment being offered a placebo (PMI Nutritional Additives) mixed into the TMR daily at a feed rate of 113 g per cow per day. Total mixed ration samples were collected daily and composited by week for nutrient analysis. Feed refusals were collected and assessed daily for dry matter (DM). Water intake for each pen was determined daily and averaged by week. Cows were milked 3 times daily and total milk yield was averaged weekly for each cow. Individual cow milk samples were collected once weekly at 3 consecutive milkings and composited for determination of fat, protein, solids nonfat (SNF), MUN, lactose, and SCC content. Somatic cell score was calculated for each cow based on SCC. Energy-corrected milk, DMI, and ECM:DMI were determined for each pen. Cow BW was determined daily and averaged by week. No significant treatment effects were found for any measures. All parameters except for SCS differed significantly by week (P < 0.03) as cow DIM increased. Block had a significant effect on milk yield, ECM, percent and kg of milk fat and protein, lactose, SNF, and ECM: DMI. A block by week effect (P = 0.03) was observed for water intake and MUN (P = 0.05). Additionally, a treatment by week effect (P < 0.0001) was observed for MUN with AD cows having lower MUN during wk 5 relative to C cows (10.5 and 12.5 mg/dL respectively). In summary, feeding AD to multiparous early lactation cows did not impact cow performance, but may affect MUN at various points during lactation.