Horses are living longer, and older horses have special nutritional requirements. Dr. David Pugh from Auburn University indicates that because of competition for feed and the effects of arthritis and failing eye sight, many older horses do not get the nutrition they need and we need to make sure they do get adequate nutrition. To be able to make appropriate recommendations on nutrition, it is a good idea for your vet to perform blood work on your senior at least once a year. The blood work will check for liver and kidney disease as well as mineral levels. If the liver or kidneys have concerns, it will have an effect on dietary recommendations. For example, if the horse has kidney disease, avoid a high protein and high calcium diet; grass-based forage with some added corn or a fat source is a better option. Protein levels for horses with kidney disease should be less than 8%, which is why grass hay is preferred over alfalfa. If the horse has liver disease, use a diet low in both protein and fat as horses with liver disease usually do better on grass-based diets with additional calories from cereal grains.
However, if there is no evidence of liver or kidney disease, Dr. Pugh recommends feeding seniors slightly more protein ranging from 12-16% because digestibility of older horses seems to decrease compared to younger horses. And if the kidneys and liver are normal, feeding alfalfa is a good choice, and adding corn oil to the diet will help maintain weight in some of these older horses. Adding a free-choice salt mineral mixture is a good idea. Of course dental disease is a major concern in older horses and senior feed is a good option because it is easily digestible and requires little chewing.