The effect of a combination of probiotic strains of Lactobacillus animalis (LA-51) and Propionibacterium freudenreichii (PF-24) fed at a total concentration of 3 × 10⁹ on total-tract digestibility of NDF, protein, and starch and on the concentration of starch in manure was assessed in a commercial study. Observations were gathered from 25 herds, ranging in total size from 80 to 6,000 cows. High groups within each herd were selected for testing. Groups ranged in size from 20 to 200 cows and were producing ≥80 lb average milk per day. Both Jerseys and Holsteins were included in the test. Group samples of manure and total mixed rations (TMR) were collected one week before and 3 weeks after the initiation of supplementation of feed with probiotics. Fecal and TMR samples were sent to Cumberland Valley Analytical Laboratory for analysis. Data were analyzed using 2-tailed paired t-test using herd as the experimental unit. There was no effect of probiotic feeding on total-tract digestibility of NDF or protein. Starch digestibility was increased (P < 0.01) and fecal starch was decreased (P < 0.01) with daily feeding of the combination of LA-51 and PF-24. When the data were limited to those herds where the initial concentration of fecal starch was ≥3%, total-tract digestibility of protein and starch increased (P < 0.05 and P < 0.0001, respectively), fecal starch decreased (P < 0.001), and total-tract digestibility of NDF tended to increase (P < 0.12). The addition of an effective combination of probiotic organisms can improve the apparent digestibility of nutrients when fed to high-producing dairy cows.