We determined the effects of a prepartum negative dietary cation-anion difference (DCAD) supplement on subsequent performance of beef cows. Forty-three multiparous cows (568 ± 73 kg of BW) were used in a completely randomized design. Prepartum cows were stratified by breed, BCS, and the previous year’s calving date and assigned to one of 2 treatments: control (CTRL; 1.75 kg·d⁻¹ of 50:50 corn gluten feed (CGF):soybean meal (SBM) mixture, DM basis) and treatment (BCLR; 0.57 kg·d⁻¹ of an anion source [Bio-Chlor, Church & Dwight Co., Princeton, NJ] and 1.13 kg·d⁻¹ of 50:50 CGF:SBM mixture, DM basis). Cows had ad libitum access to bermudagrass hay (Cynodon dactylon) and water. Daily, cows were individually penned and received supplement (CTRL and BCLR were fed for 21.8 ± 9.3 and 24 ± 9.5 d, respectively) until calving. After calving, cows and calves were weighed within 12 h of parturition and blood samples were collected from the cow. Weekly, blood samples were collected from cows, and BW of cows and calves and BCS of cows were recorded. On d 28, 84, and 140 postpartum, milk yield was recorded and milk samples were analyzed to determine energy corrected milk (ECM). Calculated DCAD of CTRL was 469.61 mEq·kg⁻¹ DM whereas BCLR was −1295.89 mEq·kg⁻¹. Cow weight and calf weight was not affected by treatment (P = 0.1154 and P = 0.9598, respectively). The ADG of cows (0.1 ± 0.043 kg), ADG of calves (1.0 ± 0.04 kg), and BCS of cows (4.97 ± 0.05; 1 to 9 scale) was not different between treatments (P > 0.05). Similarly, ECM did not differ between CTRL and BCLR (P > 0.05). Supplemental DMI was greater (P < 0.001) for CTRL (1.60 ± 0.031 kg·⁻¹) than for BCLR (1.23 ± 0.033 kg·d⁻¹). Concentrations of plasma Ca (10.67 ± 0.51 mg·dL⁻¹) and β-hydroxybutyrate (173.0 ± 9.18 mmol·L⁻¹) did not differ (P > 0.05) between treatments. Prepartum supplementation of 0.57 kg·d⁻¹ of an anion source to beef cows did not enhance subsequent cow or calf performance.