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

Abstract

The effects of brucite (BR; magnesium hydroxide) and sodium bicarbonate (SB) on ruminal fermentation characteristics were evaluated following a ruminal glucose challenge. Four Holstein steers were used in a 4 × 4 Latin square design with 4 dietary treatments: (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 morning feeding. Time required for 50% reactivity at pH 6.0 of BR and SB was 450 and 0.5 min, respectively. Ruminal pH tended to decrease (P < 0.09) 1 h after feeding (just before the glucose challenge), but ruminal 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 capacity. 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. Supplemental BR had lower (P < 0.05) average ruminal glucose concentration than SB. Buffer supplementation decreased average ruminal osmolality (P = 0.02). Ruminal alkalizing equivalence of BR and SB were similar. Neither appreciably altered ruminal buffering capacity. Although, both reduced ruminal lactate during the first few hours following a glucose challenge. Buffer supplementation may depress ruminal protozoa.