Mechanisms of Acid Absorption in the Rumen and Impacts on Subacute Rumen Acidosis

A distinguishing feature of ruminants is that they rely on anaerobic fermentation of feeds in the rumen and reticulum (collectively termed the reticulo-rumen) to supply metabolizable energy in the form of short-chain fatty acids (SCFA) and metabolizable protein in the form of microbial protein. While the production of SCFA is a nutritionally desired effect, excessive rates of SCFA production and their subsequent dissociation in ruminal fluid can lead to a reduction in ruminal pH and the onset of ruminal acidosis. This is important as the production of SCFA can be substantial. For example, Sutton et al. (2003) measured total SCFA production for Holstein cows fed moderate (40%) or high concentrate (90%) diets reporting that production equated to 79 and 90 mol/d, respectively.