Hind-gut Acidosis can be acute (sudden) or chronic (long-standing).
An example of acute hind-gut acidosis would be the pony who breaks out of his stable and gets into the feed room.
He gorges feed, and the result is a massive overflow of starch into the hind-gut. There is a sudden reduction in the pH of the hind-gut, and the healthy bacteria in the gut get very stressed at the change in pH, and begin to die.
As they die they release toxins which are absorbed into the blood of the pony. These toxins result in an inflammatory response by the body which can cause laminitis.
An example of chronic acidosis would be the racehorse who is fed on a high starch diet, with limited access to forage.
The horse was not designed to digest large amounts of starch, and as a result, there is a constant overflow of starch into the hind-gut.
This overflow has changed the racehorses’ microbiome into a less healthy one. As a result he derives less nutrient from his meals, he passes soft droppings, can show explosive behaviour, and has a poorer immune system.
He is also likely to be uncomfortable, because as well as lactic acid, the bacteria are producing gas, increasing his chances of colic.