It is well known that stress negatively affects a horse’s gastrointestinal tract and overall health. Horses can become stressed in a variety of situations that might not seem stressful to humans, so it is important for horse owners to understand their individual animal’s needs. Slight modifications to a horse’s diet, such as optimizing forage and offering certain nutrients or dietary additives, can help manage stress-related bodily changes.

“Horses do things daily that we don’t think of as stressful, but they are to horses,” explained Clair Thunes, MS, PhD, equine nutrition consultant and owner of Clarity Equine Nutrition, in Gilbert, Arizona, during her presentation at the 2023 EquiSummit, a virtual equine nutrition conference, held Sept. 5-6. “Trailering, reduced movement by being confined to stalls, active training, heat stress/hot weather, and more are all stresses horses routinely face.” Other largely unavoidable sources of stress include environmental conditions, routine care such as veterinary/farrier visits, and dietary stress due to hay variability.

“How can horse owners help horses manage these stressors that cannot be eliminated? In part, through a well-managed diet,” Thunes said, reminding attendees that forage is the foundation of every horse’s diet. “Forage is imperative. In their natural setting horses eat for 15 or more hours per day, and their gastrointestinal tracts are designed to have an almost continuous trickle of forage.”  

The general recommended amount of forage for one horse is a minimum of 1.5% body weight in a 24-hour period, which is 15 pounds for an average 1000-pound horse.

Forage alone, however, does not completely meet a horse’s minimum nutritional needs. Some horses might need a ration balancer or additional calories. Beyond meeting a horse’s minimum dietary requirements, owners can use other nutrients and dietary ingredients to support horses and combat the effects of stress.

Chromium

When horses are stressed, their cortisol levels increase, which can adversely affect metabolism, immune function, and inflammation. Chromium is involved in stress pathways, and study results show feeding organic chromium lowers cortisol levels.

Bacillus subtilis PB6

This live, spore-forming bacteria attacks and kills equine pathogens such as Clostridium difficile and C. perfringens, Streptococcus equi, and Rhodococcus equi.

“These pathogens can damage the cells lining the gastrointestinal tract, the enterocytes, which should be tightly adhered to one another forming an impenetrable barrier between the inside of the gastrointestinal tract and the horse’s circulation,” said Thunes.

These tight junctions are similar to your fingers when you make a fist—nothing can pass through those tight junctions that isn’t supposed to. Pathogens can weaken the tight junctions, such as when you relax your fists and your fingers drift apart. Now pathogens and other small molecules can cross into the blood stream where they shouldn’t be. This causes intestinal inflammation and potentially disease, she explained.  

This situation when the tight junctions break down is referred to as leaky gut syndrome.

“An inflamed gut lining can be stressful to the horse and may contribute to systemic diseases such as colitis, malabsorption, food allergies, pathogen translocation, and inflammatory bowel disease,” Thunes added.

Butyric Acid

Butyric acid is a short-chain fatty acid produced by bacteria found in the intestinal tract, making up a component of the microbiome. This molecule promotes growth of the tissues lining the gastrointestinal tract along its entire length.

 “Having healthy enterocytes enhances intestinal development, improves tight junctions, increases antioxidant levels to promote healing in the gastrointestinal tract, modulates the immune response, and reduces inflammation,” said Thunes.

Zinc

“Zinc is involved in maintenance of tight junction and epithelial barrier functions,” Thunes noted. Together with butyric acid, zinc helps maintain stronger barriers against pathogens, parasites, and toxins.

Take-Home Message

“Research into these and other ingredients is ongoing as we try to better understand how we can help horses withstand everyday stressors,” said Thunes. “Beyond these exciting technologies it is important to remember that fighting stress starts with sound management practices and a base diet that provides the horse with all the building blocks needed to be healthy in both mind and body.”

Horse owners can consult an equine nutritionist to help ensure their animals are receiving proper nutrition. They can also evaluate their management practices to make sure they’re not placing additional stress on the horse.