Despite the fact that horses evolved on a forage-based diet that is high in fiber and low in calories, some horse owners and trainers just can't resist feeding a low-fiber, calorie-dense diet.
"Horses are grazing animals," explains Katherine A. Houpt, VMD, PhD, Dipl. ACVB, a professor emeritus of Cornell University's College of Veterinary Medicine. "When they are denied access to pasture to partake in this natural activity, health and behavior issues arise, like the development of gastric ulcers and destruction of wood fences and stall walls."
To determine if horses' welfare, in addition to their health, was compromised when denied fiber, Houpt and co-author Jaime Elia assessed the "motivation for fiber" of eight mares fed two different diets, either orchardgrass hay ad libitum or a complete pelleted feed, for three weeks. The horses were also trained to press a panel to obtain a food reward.
"We found that when horses were fed pellets, they worked harder to obtain a hay food reward than when they were fed hay," said Houpt.
In addition, the researchers also found that:
- Horses fed hay spent 61.5% of their time (throughout a 24-hour period) eating, while horses fed pellets spent only 10% of their time eating,
- Horses fed pellets spent 58% of their time standing while horses fed hay spent 37% of their time standing, and
- Horses fed pellets spent 11.5% of the their time sifting through the bedding of their stall looking for food whereas horses fed hay only spent 1.2% of their time practicing this "searching behavior."
According to Houpt, "These findings clearly show that horses were motivated to work for hay when they were fed a pelleted diet, but not when they were fed a hay diet. That is, these horses showed a 'hunger for hay' when fed a pelleted diet."
The authors concluded that a reduction in dietary fiber has a major impact on the behavior and physiology of horses. They recommend feeding at least half a bale of first cutting hay per day, or offering free choice hay.
The study, "Motivation for hay: Effects of a pelleted diet on behavior and physiology of horses," is scheduled to be published in an upcoming edition of the journal Physiology & Behavior. The abstract is currently available on PubMed.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.