Influence of Feed Ion Content on Buffering Capacity of Ruminant Feedstuffs In Vitro

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Abstract
In vitro buffering capacity of 52 feeds was measured to determine the buffering capacity range within and among feed types. Feeds were analyzed for dry matter, total ash, minerals (Ca, Mg, K, Na, Cl, N, P, Si, S), and pH, titratable acidity and alkalinity, acid-buffering capacity, and base-buffering capacity (milliequivalents of acid or base required to bring .5 g dry matter suspended in 50 ml distilled deionized water to pH 4 or 9, respectively, divided by total pH change). Buffering capacity was lowest for energy feeds, intermediate for low protein feeds (15 to 35% crude protein) and grass forages, and highest for high protein feeds (> 35% crude protein) and legume forages. The concept of diet formulation for ap redetermined buffering capacity was tested. Two isonitrogenous and isocaloric diets substantially different from each other in buffering capacity were formulated using ingredients from the pool of 52 feeds. The measured acid-buffering capacity of these diets was similar to their predicted values. Acid buffering capacity was correlated with total cations and total ash. However, simple linear regression was not suffient to predict accurately acid-buffering capacity from total ash values. Further studies are needed to provide a better estimate of feed-buffering capacity.