Hay for Horses: A Question of Quality

Ask horse owners to describe a perfect flake of hay, and the diversity of responses may astonish. The owner of a plus-size pony may mention a blend of local pasture grasses, sweet-smelling and pillowy to the touch; another might specify densely packed alfalfa, bright green and laden with leaves. A third owner may extol the nutritional virtues of early-maturing timothy, with its long blades and barely-there seed heads.

Given the assortment of responses, it is safe to say that different management situations call for different hay. Italian researchers recently described three case studies in which hay caused unexpected problems in horses.^*

Wounding potential of plants. Impurities in hay are problematic on many levels, according to Catherine Whitehouse, M.S., a nutritionist with Kentucky Equine Research. “Some hays are harvested when plants are too old and stalky or extremely weedy, features that leave their nutritional value in question. When those weeds include toxic plants, hays transition from unworthy to wholly unacceptable, to be avoided at all costs.”

Somewhere in the middle lie those plants that are not poisonous but are nevertheless capable of injuring the horse, particularly the soft tissues of the mouth and the esophagus.

In the first case study presented by the researchers, three horses with no pasture access began to refuse their forage, a low-quality meadow hay. The owners also noticed blood-tinged drool falling from the horses’ mouths. On physical inspection, the oral cavities of all three horses revealed painful, bloody lesions.

The hay was examined carefully and found to contain the seed heads of yellow foxtail (Setaria glauca) and barnyard grass (Echinochloa crusgalli). Samples of plant material removed from the gingiva of the horses matched these plants. With time and new forage, the horses recovered.

Yellow foxtail and barnyard grass both possess awns, stiff bristles that develop on the grain-sheaths of certain grasses. While awns may be soft and pliable when grasses are young, as plants mature, they become stiff and sharp, capable of piercing soft tissue and becoming wedged in the throat. Migrating awns may burrow and lodge deeply in tissue, leading to abscesses.

Examples of other injurious plants include cocklebur, stinging nettle, and thistles. “Many horses relish the taste of thistles, both as young, tender plants and as more mature flowering plants, but thistles should be eradicated from pastures whenever possible,” recommended Whitehouse.

“Purchasing hay from reputable growers who understand the needs of horse owners is the first step in protecting your horse from weeds and other unwanted vegetation,” Whitehouse explained. “The second step is visual inspection of the hay prior to feeding. Ultimately, it’s up to the owner to determine what he puts in front of his horse.”

Aggravation of irritated tissue. Forage constitutes the basis for most equine diets. In the absence of pasture, hay often becomes the forage of choice. Occasionally, though, a health problem precludes the feeding of hay.

In the second case study, the researchers recount instances in which hay proved unsuitable for two horses, both of which had trouble swallowing, a condition called dysphagia: one horse was diagnosed with esophageal diverticulitis and another horse with selenium deficiency and related degeneration of the masseter muscle, the muscle responsible for closing the mouth.

Veterinarians assumed long-stem forage made swallowing more painful, so the horses were offered hay pellets softened into a slurry. Appropriately, a balancer pellet to fulfill vitamin and mineral requirements was also offered to the horses. When choosing fortification, select a scientifically formulated balancer pellet or a research-proven vitamin and mineral supplement.

“Dysphagia often requires a short-term change in diet due to the irritating nature of some long-stem forages, especially mature, stemmy hays,” explained Whitehouse. “Alternative forage sources such as pellets are fitting substitutes. All changes in diet should be made gradually whenever possible.”

Free fecal water syndrome. Two horses were identified with signs suggestive of free fecal water syndrome. Veterinarians provided treatments to reduce signs, including probiotics and steroid therapy. None of the treatments worked, however. The diets of both horses included about 22 lb (10 kg) of meadow hay and 3 lb (1.4 kg) of high-starch concentrate daily.

Both diets were eventually reworked. The amount of long-stem meadow hay was divided in half and provided by a different supplier with a notable uptick in quality. The remaining half was replaced with ground or pelleted meadow hay. The horses were allowed to graze more than they had, up to 4 hours each day, and the high-starch concentrates were replaced with low-starch fibrous mixes. The number of concentrate meals was increased from three to four. With these diet changes, the horses showed improvement in free fecal water.

The researchers summarized that “feeding different kinds of forages leads to different patterns of microbial populations in the hindgut, and remodulating the diet may change these clusters of bacteria, positively affecting the predisposition of individual horses to free fecal water syndrome to digest the fiber, and improving their fecal characteristics.”

Gastrointestinal health revolves in part on the consistency of diet. The effect of dietary changes can be moderated through the use of a hindgut buffer, designed to maintain the pH of the cecum and colon. EquiShure is a research-proven time-released hindgut buffer designed to support gastrointestinal health.

^*Cavallini, D., L. Panazzi, E. Valle, F. Raspa, D. Bergero, A. Formigoni, and I. Fusaro. 2022. When changing the hay makes a difference: A series of case reports. Journal of Equine Veterinary Science 113:103940.