Neutralization of Acid in the Rumen by Magnesium Oxide and Magnesium Carbonate

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Abstract
Two reagent and 2 feed grade magnesium oxides and reagent grade magnesium carbonate, sodium bicarbonate and calcium carbonate were evaluated to ascertain their ability to neutralize acid in the rumen. Rumen fluid pH was increased in vitro, compared to the control, by antacid compounds, and their increases ranked: calcium carbonate < feed grade magnesium oxide A < light magnesium oxide and feed grade magnesium oxide B < heavy magnesium oxide < magnesium carbonate < sodium bicarbonate. Titrations at constant pH''s ranging from 3.0-7.5 indicated that these magnesium compounds were reactive at pH''s normally in the rumen although reactivity decreased with increasing pH. Intraruminal doses of feed grade magnesium oxide A and calcium carbonate did not change rumen fluid pH as compared to the control treatment; increases in rumen fluid pH for other compounds ranked: feed grade magnesium oxide B < magnesium carbonate < heavy magnesium oxide. Feeding of heavy magnesim oxide or magnesium carbonate increased rumen fluid pH as compared to the control diet. Feeding feed grade magnesium oxide B in 3 quantities to cattle resulted in proportional increases in fecal pH and fluidity of feces. Two feed grade magnesium oxides differed in their ability to neutralize acid in the rumen.