Some cows may be predisposed to subacute ruminal acidosis
(PHYSorg.com Biology)

Cattle with subacute ruminal acidosis suffer from a number of low-level ailments that affect productivity. A research team led by University of Illinois scientists has documented changes in pH, microbiome, and rumen epithelial cells in SARA-affected cows. Results indicate that some animals may be predisposed to SARA because of an overabundance of certain bacteria.