Use of sodium bicarbonate, offered free choice or blended into the ration, to reduce the risk of ruminal acidosis in cattle

Abstract

A study was conducted to determine whether feeding sodium bicarbonate (SB) reduces the risk of subacute ruminal acidosis in cattle fed high concentrate feedlot finishing diets. The experiment was conducted as a replicated 3 × 3 Latin square design with two squares and 2-wk periods. Three mature, non-lactating Holstein cows were allocated to square 1 and three mature Jersey steers were allocated to square 2. The cattle were ruminally cannulated and gradually adapted to a high concentrate diet before starting the experiment. The basal diet contained approximately 80% stream-rolled barley, on a dry matter (DM) basis, and was offered for ad libitum intake. Treatments were: control (no SB), control diet with cattle given free choice access to a SB mixture consisting of 70% SB and 30% dried molasses (free choice SB), and control diet supplemented with SB (7 g SB kg-1 DM; mixed SB). Ruminal pH was measured at the end of each 14-d period for 3 continuous days using an indwelling pH system. Dry matter intake (DMI) was not affected by treatment. However, SB intake depended upon type of cattle and method of provision (P = 0.04); cows had higher SB intake when it was mixed into the diet (57.8 vs. 17.4 g d-1), whereas steers had higher SB intake when SB was provided free choice (129.1 vs. 56.1 g d-1). Ruminal pH characteristics (mean, maximum, minimum, hours, and area under a threshold pH of 5.8 or 5.5) were not affected by treatment. Although neither method of delivering SB reduced the total time each day that pH was below the pH thresholds used to indicate subacute ruminal acidosis, the number of long (> 4 h) continuous bouts of acidosis (pH ≤ 5.8) was reduced (P = 0.01) when SB was mixed into the ration compared with the control. When offered free choice, intake of SB was highly variable among animals and from day-to-day and was inversely correlated to DMI. However, there was no correlation between SB intake and ruminal pH indicating that, when given the opportunity, cattle did not select SB to help prevent ruminal acidosis. Providing SB, either free choice or mixed into the ration, did not eliminate subacute ruminal acidosis in cattle fed high-grain diets. However, mixing SB into the ration reduced the number of long bouts of ruminal acidosis, which could potentially reduce the negative consequences of ruminal acidosis on feed digestion. Key words: Acidosis, beef cattle, high-grain diets, ruminal pH, sodium bicarbonate