Melatonin and Cool Diets for Hot Horses

Some horses naturally run “hotter” than others. Imagine, for example, the hypersensitive chestnut filly that can’t cope with the nubs on a currycomb during daily grooming. When horses are consistently nervous or high-strung, daily care becomes increasingly challenging for owners, and travel to new locales becomes a potential nightmare. What can you do to help mellow your horse?

“Various nutritional supplements claim to calm nervous horses,” said Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research. “Ingredients in such products include B vitamins and magnesium to support the nervous system, the amino acid tryptophan, and various herbs such as licorice and valerian roots, chamomile, and Indian ginseng. In Australia, Kentucky Equine Research offers B-Quiet and B-Quiet Paste, both of which contain vitamin B1 (thiamine) and magnesium.”

Although not studied yet in horses, the effects of melatonin in other animal species, including humans, suggest this “sleep hormone” may be a viable option in the future. Melatonin is synthesized in the brain from tryptophan and secreted from the pineal gland, an egg-shaped gland tucked between the left and right hemispheres of the brain.

Hormone levels are influenced by light levels and therefore fluctuate based on time of day and season. In dogs*, melatonin helps treat phobias (e.g., thunderstorms, fireworks) and calms anxious patients during veterinary examinations. Most recently, melatonin proved useful as a premedication to decrease the volume of the medication propofol required to induce anesthesia.

At this point in time, the use of melatonin as a calming agent in horses remains hypothetical. Owners are discouraged from simply offering melatonin products intended for other species to their horses as safety has not been established. To date, melatonin is primarily of interest in horses for reproductive purposes, particularly for advancing the breeding season with artificial lights.

“While awaiting the green light for melatonin use in horses, consider offering a ‘cooler’ diet,” advised Crandell.

A “cool” diet refers to one high in fibrous feeds that ferment slowly in the hindgut. Pasture, hay, and chaff fall into this category and can be consumed for 16 to 18 hours a day, rather than within minutes as observed with traditional textured or pelleted feeds. On the flip side, alfalfa is considered a “hot” forage due to its energy content and should be avoided.

“Other hot foods such as oats, corn, barley, and molasses, should also be sidelined as these are digested in the small intestine and increase blood sugar levels, potentially contributing to unwanted nervous or excitable behaviors,” Crandell noted.

If using supplements, Crandell warns, “Be cautious when choosing any nutritional supplement, especially those containing herbs. Those products may contain byproducts or contaminants that are banned during competition.”

*Niggemann, J.R., A. Tichy, M.C. Eberspächer-Schweda, et al. 2019. Preoperative calming effect of melatonin and its influence on propofol dose for anesthesia induction in healthy dogs. Veterinary Anaesthesia and Analgesia. S1467-2987(19)30115-1.