This study was conducted to evaluate the supplementation of anionic salt products to pre-partum diets on dry matter (DM) intake, nutrient digestibility, blood metabolites, and milk composition of cows during the transition period. Twenty-four Holstein cows [614±21.3 kg body weight (BW) and 2.0±0.9 parity number] were blocked by parity and expected calving date, and randomly assigned to the following treatments: Animate (ANI), anionic salts (Animate, Phibro Animal Health, Teaneck, US) fed at 2.85 %DM; or Meganion (MEG), anionic salts (MegAnion, Barentz Animal Nutrition, Hoofddorp, The Netherlands) fed at 1.85 %DM. Treatments targeted -150 mEq/kg diet DM and were provided starting at 30 d of the expected calving date. Treatment effects were evaluated until 56 days in milk. Pre-partum diets presented -55.9 and -32.1 mEq/kg diet DM for ANI and MEG, respectively. Dry matter intake and BW were similar across treatment groups during the pre-partum and post-partum periods. Post-partum body condition score tended to be greater for MEG. Pre-partum urine pH was similar between treatment groups (6.33 and 6.49 for ANI and MEG, respectively). Cows fed MEG had greater neutral detergent fibre digestibility on weeks 5 (53.2 vs. 49.8 %) and 6 (53.5 vs. 49.6 %) of lactation than ANI. Serum concentration of Mg was greater in cows fed MEG during the pre-partum. No treatment differences were found for blood concentrations of ionized Ca, non-esterified fatty acids, beta-hydroxybutyrate, or insulin. Milk yield was not affected. Both anionic salts maintained adequate calcium metabolism during the transition period and resulted in similar performance.