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ii A study was conducted to determine whether feeding sodium bicarbonate (SB) reduces the risk of subacute acidosis (SARA) in cattle receiving high concentrate diets. Twelve Hereford cross heifers (Exp.1) and six ruminally cannulated animals (Exp. 2; three Jersey steers and three Holstein cows), previously adapted to a high concentrate diet, were used in 3 _ 3 Latin square designs to study the effects of SB on feed intake, ruminal pH, ruminal fermentation and blood characteristics. Animals were provided ad libitum access to a control diet containing steam-rolled barley, barley silage, and a supplement at 80, 12, and 8 % (Exp. 1) and 81.2, 12.0 and 6.8% (Exp. 2) (DM basis), respectively. Treatments were: control, control with free choice access to a SB mixture offered as 30 % dried molasses and 70 % SB (free choice SB) and control diet supplemented with 0.7 % SB (DM basis) (mix SB). Periods consisted of 21 d (Exp. 1) or 14 d with 11 d adaptation and 3 d of continuous ruminal pH measurements using indwelling electrodes (Exp. 2). Mean dry matter intake for Exp. 1 and 2 was not affected by treatment. Sodium bicarbonate intake differed when provided free choice verses when mixed into the die