Horses rely on fermentation for optimal digestion of feedstuffs and energy production. Hindgut digestion, which occurs in the cecum and large colon, progresses most efficiently when horses are allowed continual access to forage and limited access to feedstuffs that could upset the pH of the cecum, including large grain meals.
Fermentation is achieved through the machinations of billions of protozoa, fungi, and bacteria. Together, these microbes convert carbohydrate-based contents, essentially plant-based fiber, into volatile fatty acids (VFA), which provide energy to the horse. If soluble carbohydrates, such as those found in large supply in grain meals, find their way into the hindgut, some lactate might be produced.
An overproduction of lactate can shift the pH of the hindgut to a more acidic state, which may cause problems. When a drop in pH occurs, called hindgut acidosis, some of the beneficial fiber-digesting microbes die off. Digestive efficiency drops as a result. In many horses, this manifests as poor appetite, crabby disposition, recurrent colic, and onset of certain stable vices, such as stall-walking and cribbing.
To offset this, horse owners should scrutinize feeding management. Hindgut acidosis is rarely caused by what is fed but rather how it is fed. Here are three strategies to ward off hindgut acidosis:
Good-quality forage should be offered at all times, so the hindgut is continually in “processing mode.” Forage may be pasture, hay, or hay-based products such as cubes or pellets. Forage selection should be based largely on the nutrient needs of the horse.
Concentrate meals should not exceed approximately 0.5 lb (0.23 kg) per 100 lb (45 kg) of body weight (5 lb for a 1,000-lb horse; 2.25 kg for a 450-kg horse).
If a horse requires more than 5 lb (2.25 kg) of concentrate per day, divide total daily allotment into separate meals. Feeding three or four concentrate meals, evenly spaced throughout the day, is more beneficial to the horse than huge meals.
Some horses, especially those that are asked to perform intense exercise, must consume large grain meals to fuel performance. Hindgut acidosis can be curbed by feeding GNF Pellet, a time-released buffer that raises the pH of the hindgut and eliminates signs of acidosis.