Today I am going to talk about digestion of nutrients in older horses. In humans, nutritional requirements change with age, but there is not a lot of information about the changes in digestion as horses age. One older study indicated that geriatric horses have decreased digestion of phosphorus, fiber, and crude protein. It is possible these horses had parasites and may have also had dental disease, as this was not discussed in the study.
Due to the lack of current information, a recent study was performed on 17 stock-type mares ranging in age from five to 28 years old. Each horse was dewormed, had no significant dental disease, and was fed three different diets consisting of hay only; hay plus a starch and sugar-rich concentrate; and hay plus a fat and fiber-rich concentrate. Each diet was fed for five weeks and feces and urine was evaluated to determine digestibility. Kentucky Equine research indicates that the study found older horses in good health can absorb nutrients as well as younger horses. There was no difference in digestibility of energy, neutral detergent fiber, crude protein, fat, calcium, and phosphorus. So results of this study lead us to believe that there is no reason to change diets as a horse ages. This is assuming the horse has good dentition because if he has dental problems with missing and cupped out teeth, then a senior diet may be beneficial. The senior diets require less chewing so when your veterinarian is performing your horse's semi-annual exam, ask them to check your horse's teeth, check for parasites, and discuss the diet they recommend for your horse. You may not need to change diets just because your horse is getting older.