Older horses begin to absorb less nutrients from their diet as their intestinal tract ages. It is also widely believed that the ability to synthesize some vitamins, such as B & C, decreases with age. It is important to supplement them with highly absorbable organic minerals and vitamins as well as a digestive aid such as yeast and/or probiotics to support feed efficiency. Many older horses also benefit from supplementation with Glucosamine and Chondroitin.  It is also critically important to maintain good dental health via annual exams by a qualified equine dental health professional. If your older horse is missing teeth, or having trouble chewing hay (as evidenced by clumps or wads of chewed hay), you may need to add an alternative forage source such as chopped hay, soaked beet pulp, or wet hay cubes. Continue to offer some hay to encourage the horse to chew, which produces saliva and protects the intestinal tract from ulcers.