by Dr. John Sylvester of Mars Horsecare US, Inc.
As horse owners, we know that our horses are different from production animals such as pigs and cows; however, most of us rarely stop and take the time to understand why.
Modern horses come from the genus Equus that branched off a common ancestor about 5 million years ago. And about 5 thousand years ago, horses and humans met for the first time. Humans fell in love with horses and we decided that horses would be a part of our lives from that point forward.
During the past five thousand years, we have selected characteristics from many different horses that have developed into breeds of all different shapes and sizes. Although five thousand years is a long time, from a genetic standpoint is a matter of only a few seconds. So, even though many horses may look different, their physiology (i.e., the structure of their gastrointestinal tract) has not changed much and we must understand that in order to keep our horses healthy.
The GI tract of a horse is divided into 3 major compartments, the stomach, the small intestine and the hind-gut which contains the cecum and large intestine. Feedstuffs are digested and absorbed in the stomach and small intestine, while fiber is fermented in the hindgut. The hindgut makes up for approximately 70% of the horse’s gastrointestinal tract and is designed to ferment forage (and specifically fiber). Forage can be from pasture, hay, silage, or any other plant material. Fiber is absolutely necessary to maintain horse health. Through a complex partnership between horse and microorganisms; fiber is fermented by microbes, which produce beneficial end-products that the horse can use for energy. Fiber is also needed to maintain gut health.
Horses are unique animals with specialized digestion to allow them to eat forage. We must not forget that modern day horses do more work in recent times than in years past and are eating more feed to get the calories needed for optimal performance. The horse’s requirement for forage, however, has not changed — so whatever your horse does for a living, feed at least 1% of the horse’s bodyweight from forage. For example, an 1100 lb quarter horse should get at least 11 lbs of hay per day minimum.