Ruminal alkalizing potential of brucite and sodium bicarbonate in feedlot cattle diets

Abstract

Objectives: The effects of brucite (BR; magnesium hy-droxide) and sodium bicarbonate (SB) on ruminal fermen-tation characteristics were evaluated following a ruminal glucose challenge.Materials and Methods: Four Holstein steers were used in a 4 x 4 Latin square design with 4 dietary treat-ments: (1) control (CTL; no buffer), (2) 0.5\% BR, (3) 1\% BR, or (4) 1\% SB. The basal diet contained 70\% steam -flaked wheat. On the collection day, 500 g of glucose was introduced through a ruminal cannula 1 h after the morn-ing feeding. Results and Discussion: Time required for 50\% re-activity at pH 6.0 of BR and SB was 450 and 0.5 min, re-spectively. Ruminal pH tended to decrease (P < 0.09) 1 h after feeding (just before the glucose challenge), but rumi-nal fluid buffer capacity was greater (P = 0.01) 1 h before feeding for CTL than buffer-supplemented diets. Average pH was not influenced by buffer supplementation. Buffers tended (P = 0.07) to reduce average ruminal buffer capac-ity. Ruminal pH and lactate had an inverse relationship (r = -0.59). Average ruminal VFA concentration tended to be lower (P = 0.06) for SB than BR. Compared with CTL, buffers decreased (P = 0.03) ruminal protozoa. Supple-mental BR had lower (P < 0.05) average ruminal glucose concentration than SB. Buffer supplementation decreased average ruminal osmolality (P = 0.02).Implications and Applications: Ruminal alkalizing equivalence of BR and SB were similar. Neither apprecia-bly altered ruminal buffering capacity. Although, both re-duced ruminal lactate during the first few hours following a glucose challenge. Buffer supplementation may depress ruminal protozoa.