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A metabolism experiment was conducted to evaluate the effects of daily feeding of encapsulated Megasphaera elsdenii (M. elsdenii) NCIMB 41125 along with a one-time dose of Lactipro NXT (MS Biotec) on dry matter intake (DMI), rumen pH, in vitro lactate disappearance, volatile fatty acid (VFA) concentration, and lactate concentration. Ruminally cannulated crossbred steers (n = 40, initial BW 437 ± 98 kg) were individually fed a finisher diet consisting of 70% steam-flaked corn, 18% modified distillers grain plus soluble, and 7% alfalfa hay. Treatments were control (Con) steers which were given no M. elsdenii and four treatments that received LactiproNXT on day 1 and were given 0 (Drench), 1×106 (Low), 1×107 (Medium), or 1×108 (High) CFU of encapsulated M. elsdenii daily throughout the experiment fed as a top-dress. Adaptation to the finishing diet was accomplished in 19 days for Con steers and 9 days for steers in the Drench, Low, Medium, and High treatments. The experiment included five continuous periods: step-up (d 1-19); finishing (d 20-88); feed restriction (d 89, 24-h full feed restriction); challenge (d 90, cattle were fed at 150% of max DMI from finishing period); and recovery (d 91-94). Data were analyzed using the MIXED procedure of SAS with linear and quadratic effects of dose with drench as the intercept. There were no significant differences for DMI in the step-up, finishing, or challenge period. In the recovery period, DMI was greater for Low, Med, and High compared with Drench (P = 0.07) and there was a tendency for a linear increase in DMI with increasing the dose of M. elsdenii (P = 0.11). Recovery period DMI, expressed as a percentage of pre-challenge intake, was greater (P = 0.05) in steers fed M. elsdenii daily compared with Drench steers, and increased linearly (P = 0.06) as dose of M. elsdenii increased. Rumen pH in steers fed M. elsdenii daily was greater (P < 0.01) during the feeding period and tended to be greater during the challenge (P = 0.14) and recovery (P = 0.11) periods when compared with the Drench treatment. In vitro lactate disappearance tended to be greater (P = 0.13) in steers given M. elsdenii daily when compared with Con and Drench on d 88. For days 90, 91, and 92 combined, a treatment effect was observed for in vitro lactate disappearance with steers in the Low, Med, and High treatments having greater (P < 0.05) disappearance than Con steers, and Med steers having greater (P < 0.05) disappearance than all other treatments. An accelerated step up is possible with the drench and daily feeding of M. elsdenii. Daily feeding of M. elsdenii has a positive effect on cattle during and after an acidosis challenge event. [ABSTRACT FROM AUTHOR]