This is what Gizmo is at the vet for:

"Rumen acidosis is most likely to occur shortly after animals consume excessive amounts of grain starch. This is most likely to occur soon after animals are introduced to pellets, or when pellet feeding is re-commenced following an interruption. Limited or no access to roughage of an effective fibre length means that stock will spend less time chewing and will produce less saliva, which results in reduced ingestion of bicarbonate and phosphate buffers normally supplied to the rumen in salivary secretions. Rapid fermentation of starch causes high levels of lactic acid to form quickly in the rumen, killing essential gut microflora, damaging the mucosal lining, and drawing in body fluid. This leads to rumen stasis, dehydration, and diarrhoea. Severely affected animals may develop systemic acidosis, abdominal or systemic infections, and laminitis. Animals may die either acutely due to overwhelming acidosis or as a result of secondary complications.

Large, strong, young animals with excellent appetites are more at risk. Rapid engorgement of a ration due to hunger or competitive feeding will predispose stock to rumen acidosis. If a single animal is showing clinical signs of acidosis it will indicate a high probability of subclinical acidosis in the rest of the herd."