The changes are subtle–mild stiffness, deepening hollows above the eyes in the evening light, a spine that dips a bit more. "How old is he?" friends ask. "Oh, about 15," you answer year after year until you run across his papers and discover your beloved companion is nearly 25. At some point, your vision of your horse shifts. You no longer picture him sailing over fences. Instead, you see him nibbling the green grass beneath the fence in the summer evenings. You begin to worry about the end of your years together and seek ways to prolong those years. Welcome to ownership of an old horse.

In practical terms horses are considered "old" around age 20. However, an increasing number of horses are living much longer. At the Tufts University School of Veterinary Medicine¹, for instance, the percentage of horses over age 20 presented to the teaching hospital rose from 2.2% in 1989 to 12.5% in 1999. Anecdotally, it is not uncommon for horses to live well into their 30s and even early 40s. Ponies tend to be overrepresented in the population of aged horses. In a National Animal Health Monitoring Systems study that surveyed owners of 10,000 U.S. equines, 15.2% of ponies were older than 20.

So what can you do to keep your horse happily in that pasture for years to come? Aging is inevitable, its progression determined by a combination of genetics, care, and luck. Ideally, we would breed for traits that enhance longevity: strong feet and legs, good dental occlusion, and a decreased susceptibility to life-shortening diseases. In that perfect world horses would have access to free exercise, a natural diet of mixed grasses with small amounts of concentrate, and consistent hoof, medical, and dental care throughout their lives. These early factors help a horse reach his 20s in good health.

While owners can’t control genetics and luck once a horse is born, they can impact longevity through lifelong thoughtful care–attention to housing, nutrition, hoof care, exercise, and preventive medical care such as parasite control and vaccination