The study suggests that equine obesity may result from natural grazing behavior instead of the overfeeding of grains and other feed supplements, which defies conventional thinking on equine weight matters. The majority of horses examined in the study were fed primarily pasture and hay with very little grain and concentrate.
Instead of overfeeding of grain and concentrates, the evidence indicates that improved forage and lack of exercise are the two most common contributing factors in equine obesity. Thatcher believes this may result from the fact that many pasture forages have been fortified with the goal of improving weight gain and productivity of cattle and other food animals, with little thought given to how these forages might affect horses, which often share the same types of pastures. In addition, the majority of the horses studied were under-exercised. They were left on pastures to eat, but did not have an actual exercise regimen.
Horses today are managed much differently from their evolutionary roots, indicated Dr. Pleasant. The horse evolved as a free-roaming grazer on sparse pasture types, he said. Later the horse served primarily as a work animal, serving as a source of transportation and draft power. Today, most horses serve as companions and light performance animals, he said.
We can see with increased nutrition and lack of exercise how these animals could drift toward being overweight, he said.