The study was conducted to evaluate the effect of adding 2 new formulas of dietary buffer on feed intake, nutrient digestibility, rumen pH, blood metabolites, and milk production of dairy cows. Nine multiparous cows (BW = 594 ± 46 kg; DIM = 120 ± 28 and milk yield = 46.6 ± 3.4 kg/d) were randomly assigned to a triplicate 3 × 3 Latin square. Treatments were varying source and proportion of dietary buffer (DM basis): (1) 1.12% sodium bicarbonate (SB), (2) 0.87% high buffering capacity formula contained Na (HBNa), and (3) 0.74% high buffering capacity formula contained K (HBK). Each experimental period consisted of 14 d of adaptation and 7 d of sampling and cows were fed with high concentrate diets (62% of DM). Buffering capacity was 102, 150, and 137% of a pure NaHCO₃ for SB, HBNa and HBK, respectively. The amount of Na and K were 27 and 0, 31 and 0, and 25 and 6%, respectively, for SB, HBNa, and HBK. Data were analyzed using Mixed Procedures of SAS with a model consisting of fixed effects of treatment, square, and period, and random effect of cow within square. Intake of DM tended (P < 0.06) to be lower with HBK (20.6 kg/d) than SB (21.0 kg/d) and HBNa (21.2 kg/d). However, no treatment effects were observed on rumen pH (averaged 5.88) and DM digestibility in the total digestive tract (averaged 79.4%). Yields of actual milk (38.1 kg/d) and 3.5% FCM (31.6 kg/d) were not affected by treatments, whereas yields of SCM (P < 0.07) and milk fat (P < 0.10) tended to be greater with HBK than SB and HBNa. Contents of milk fat, protein and lactose were greater (P < 0.05) with cows fed HBK than with cows fed SB or HBNa, as a result, milk efficiency (milk yield/DMI) improved with HBK (1.86) compared with SB (1.80). Blood concentration of Ca was higher (P < 0.01) with HBK compared with SB and HBNa (10.4 vs. 9.7 and 9.9 mg/dL, respectively). Blood glucose concentration also tended (P < 0.08) to be greater with HBK (64.7) versus HBNa (58.8) and SB (58.4 mg/dL). These results indicated that under the current experimental condition, supplementation of dairy cow diet with a high buffering capacity buffer contained 6% K decreased DMI, improved milk composition and milk efficiency of dairy cows.