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Effects of sodium bicarbonate on reducing acidosis in cattle Paton, Laura Jane


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.l) 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 x 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 steamrolled 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 l i 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 diet (P < 0.0001) in Exp. 1 (2.1 vs. 55.3 g/d) and cows (17.4 vs. 57.8 g/d) and steers (129.1 vs. 56.1 g/d) in Exp. 2, respectively. Intakes of SB also tended to differ amongst animals (P < 0.07) in Exp. 1 and 2. Treatment had no affect on ruminal volatile fatty acids or blood variables (Exp. 2). Ruminal pH characteristics (mean, minimum, hours and area under a respective threshold pH < 5.8 or 5.5) were not affected by treatment (Exp. 2). Although neither form of SB supplementation eliminated SARA, the duration of bouts of severe SARA (pH < 5.5) tended (P < 0.11) to be reduced for animals fed free choice SB and mix SB compared to control. Of the two approaches of delivering SB, animals consuming free choice SB had shorter bouts of SARA (P < 0.05) and a tendency towards fewer of these bouts becoming severe compared to those animals consuming mix SB (P = 0.09). However, the intake of SB offered free choice was highly variable, and even when intake of SB exceeded the recommended level, there was no correlation between SB intake and ruminal pH, indicating that other factors such as feed intake, primarily influenced ruminal pH. In conclusion, providing SB did not eliminate acidosis in cattle fed high grain diets, but offering SB free choice may have small, positive effects on reducing severity of acidosis.

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