Information presented at the 2020 American Association of Equine Practitioners (AAEP) Convention covered feeding for optimal digestive health for a performance horse.
Decreased access to forage, increased reliance on meal feeding, feeding large amounts of high-starch meals with grain-based components, increased stall confinement, stressful training environment, and overuse of non-steroidal anti-inflammatory drugs (NSAIDs) can all cause problems with a horse's GI tract.
Forage is essential for a healthy intestinal microbiome, and fiber is especially essential for hind gut microbes. A horse should be fed a minimum of 1% of body weight per day of forage, but a better target is to feed 1.5-2% of body weight.
Grazing counts for forage intake. According to Kelly Vineyard, PhD, a senior nutritionist at Purina Animal Health, it turns out that horses eat faster and at a higher rate when limited to pasture availability for less than four hours a day. For example, if pasture is restricted to less than four hours of grazing time, a horse will eat 1 kg/hour. If the horse is on pasture for more than four hours per day, then it eats at an amount of about 0.5 kg/hour.
A horse grazing for six hours will consume forage in an amount comparable to 3.7 kg or 8.2 pounds of hay.
Vineyard noted that small-hole hay nets help to mimic grazing behavior if pasture is unavailable.
Concentrates pose significant challenges to the equine intestinal tract. Vineyard recommended offering <2 grams starch/kg body weight per meal to prevent starch overload in the hind gut. At that threshold, the small intestine can digest starch with little spill-over into the large intestine, where it will ferment. A sound recommendation is to feed hay before a concentrate meal to slow the rate of intake of the concentrate.
Many concentrates also contain added fat and fiber, which is helpful to reduce the reliance on starch and can serve as primary energy sources instead of feeding non-structural carbohydrates.
Feed additives and supplements should be used only as a dietary adjunct. Vineyard recommended following a “test RIDE.” The RIDE stands for Research, Ingredients, Dose and Efficacy, and horse owners should understand each of these before giving a supplement to his or her animal.
When a transition in feed is made, gradually change the amount and type of feed—this also applies to a change in a source or type of hay or forage. For example, a horse not acclimated to pasture should be introduced gradually over a period of days. Changes in hay should be done over a few days up to two weeks. Concentrates should be modified at the rate of 0.5 kg/day.