There are 2 types of rumen acidosis: subacute rumen acidosis (SARA) and acute rumen acidosis. Subacute rumen acidosis occurs when the balance in the rumen is disturbed, and the pH has dropped between 5.5 and 5.0. Main culprit of the increased acidity is the Streptococcal bacteria. When these lactic acid producing bacteria increase, the pH drops further, and eventually cause acute rumen acidosis.