The control of latent ruminal acidosis

The major item to assess ruminal acidosis is the mean pH of rumen juice for several hours after a meal. Other criteria have been proposed, however they are closely related to the mean pH and do not provide more relevant information. Various types of measurements can be performed on feeds, or diets, to evaluate the risk of latent acidosis. Individual feeds can be assessed in terms of buffering capacity, in vitro fermentability or pH drop capacity, and in sacco short term (4h) DM diseappearance. Other parameters can be measured, such as in particular the degradable starch for starchy ingredients. Otherwise, the cation-anion balance can be calculated to assess one of the components of feed and diet acidogenicity. Diet fibrosity is a major factor of variation of the risk of acidosis. In fact, there are two components of fibrosity: the chemical fibrosity, assessed by the dietary NDF (NDF%DM > 35%), and the physical one, assessed by either the mean particle size (MPS > 4mm) or the dietary DM retained by a 2mm aperture sieve (P2 > 40%DM). It is also possible to combine these two types of parameters. Fibrosity items are very important because they determine the chewing activities and thus the salivary buffer recycling and the liquid flow throughout the rumen. These items seem to be more influent than those predicting the VIA production. Other aspects affect ruminal acidosis such as the level of intake and the role of some microbial sub populations in the rumen such as the protozoa. Otherwise, beyond the feeding factors, diets can be corrected to prevent acidosis by supplementation of buffer substances or probiotics. The proposed equations and recommendantions allow to integrate various items to formulate diets preventing the risk of latent acidosis.