Nutrient Digestibility in Horses: Does It Change with Age?

I receive emails from Kentucky Equine Research (KER) with articles on feeding issues in the senior horse. The following was in an email dated August 9, 2017. I have attached it below as a point of information (mine and yours!) I overwhelmingly deal with seniors, so I see more than most owners see in their experience with horses. Nevertheless, I am always learning!

For the most part, I don't have a great many issues keeping weight on the senior horses in my care; I monitor them closely, feed them as individuals, adjust their feed if they seem to be gaining or losing, obtain special feeds or feeding protocols if necessary (e.g., wetting feed), and consult with the vet. If there's an intractable issue, sadly, it often has to do with end-of-life changes.

Articles like the one below help me as I make decisions about the horses' care.

The population of horses over the age of 20 has increased in recent history, thanks to better healthcare and increased scientific knowledge of the ageing process. Many horsemen believe that diets should be more heavily fortified as horses age in order to make up for losses in digestive efficiency. New research is challenging this notion, though.

Healthy horses may not experience declines in digestibility as years pass, but some horses, especially seniors, with medical or physical conditions are at risk for impaired nutrient absorption.

A study conducted at Michigan State University tested the digestibility of three different diets in both senior (aged 19-28 years) and young adult (aged 5-12 years) horses*, all of whom were healthy. Energy sources of the diets came from fiber, carbohydrate, or fat. Feed, fecal, and urine samples were analyzed and measured for crude protein, energy, fat, and minerals, including calcium, phosphorus, magnesium, sodium, potassium, copper, iron, zinc, and selenium. Interestingly, total digestibility of macronutrients appeared to be similar in both adult and senior horses.

Healthy horses may not experience declines in digestibility as years pass, but some horses, especially seniors, with medical or physical conditions are at risk for impaired nutrient absorption. Case in point, dental problems can lead to improper chewing, making it harder for digestive enzymes to break down food for absorption. A soft, soaked diet that meets all nutritional requirements without having to chew is helpful in this situation.

In addition, horses with chronic parasite problems could have scarred tissue along the digestive tract, reducing function. A horse recovering from heavy parasite loads may need smaller, more frequent meals with extra nutrient fortification to ensure needs are met. A Kentucky Equine Research nutrition consultant can help provide solutions for overcoming these and other nutritional challenges.

Healthy, aged horses may not have different nutritional requirements than their younger counter parts. However, horses of any age with specific concerns may in fact need special dietary modifications. Be sure to always provide fresh water and good-quality forage as the foundation of a healthy diet. Work with a veterinarian and nutritionist to provide the best healthcare and ration for your horse, based on individual needs over a lifetime.

*Elzinga, S., B.D. Nielsen, H.C. Schott, J. Rapson, C.I. Robison, J. McCutcheon, R. Geor, and P.A. Harris. 2017. Comparison of nutrient digestibility between three diets for aged and adult horses. Journal of Equine Veterinary Science. 52:89.