Eating Green.

High-fat diets may be as unhealthy for horses as they are for humans.

An article by Clare Illingworth, SPARK writer, University of Guelph.


Bucolic images of horses feeding on verdant pastures are fading from sight in North America’s equine industry. Today,many horses spend much of their time confined to stalls,where they receive specialized feeds. For some,their menus are high in fat, which is believed to be more conducive to performance ability.But putting such distance between genetic heritage and modern practices may not be a healthy practice,researchers say,because stepping away from horses’ natural food sources could be affecting the way they store and release muscle energy during exercise. And that ’s critical for all equine athletes.

Prof.Jill McCutcheon, Pathobiology, has teamed up with Prof.Ray Geor and PhD student Shannon Pratt of the Department of Animal and Poultry Science to determine the differing impacts of high-fat feeds and common starch feeds on glucose regulation in the blood and muscles of young horses.High-fat feeds have become increasingly popular because they maintain weight without making making a horse “hot,” an industry term for having too much energy. “There is little information about how diet affects horses,” says Geor. “We know they rely on carbohydrates such as glucose for energy during exercise, but we don’t know how this supply is regulated or replenished.”

Adds McCutcheon: “Glucose regulation affects every aspect of your body, including growth and performance. People feed their horses every day, but we know so little about how nutrients are used at the cellular level.” In athletes — humans and horses alike — glucose provides fuel for the body (surplus is stored in the muscles as glycogen). Glucose, which comes from carbohydrates such as starches in grains, is dispersed through the blood. Insulin, a hormone, senses high levels of this blood sugar and triggers an appropriate glucose absorption by the muscles. Increasing the amount of fat in a diet allows the starch content to be lowered, so insulin is released less often. But this may ultimately lower insulin sensitivity, meaning it’s difficult for the horse to properly digest starches. It’s believed this affects insulin, blood glucose and muscle glycogen.

“A high-fat diet is used by humans suffering Type 1 diabetes because their bodies don’t create the required amount of insulin,” says Pratt. “Caregivers are feeding the same diet to their horses without really considering the implications.” Physical training may alter this affect. Tech-nology used during human clinical diabetic research will be used to measure the rate insulin removes glucose from the blood. It’s anticipated that although fat-supplemented diets may alter the ability to digest starches when horses aren’t working, physical training may lessen the impact and thus reduce con-cerns about the starch content of the diet.

The project began this winter with 12 horses. It’s sponsored by the E.P. Taylor Fund, the Equine Research Fund and the Ontario Ministry of Agriculture and Food. Other researchers involved are Prof. John Burton of the Department of Animal and Poultry Science, veterinary student Carleen Foot and pathobiology technician Leah Rae Read.