Metabolic Magic

When we humans engage in highly strenuous exercise for extended periods, our bodies begin to metabolize  reserves of glycogen and fats.  As these stores are depleted our cells run out of energy and we become fatigued and cannot continue until those reserves are replenished.

The metabolism of sled dogs, like those who run in the Iditarod, respond much differently to extended periods of physical activity.  According to Michael Davis, an associate professor of veterinary physiology at Oklahoma State University and an expert in animal exercise:

“Before the race, the dogs’ metabolic makeup is similar to humans. Then suddenly they throw a switch — we don’t know what it is yet — that reverses all of that. In a 24-hour period, they go back to the same type of metabolic baseline you see in resting subjects. But it’s while they are running 100 miles a day.”

Amazing stuff!  A recent article in the New York Time states that:

In fact, sled dogs in long-distance racing typically burn 240 calories a pound per day for one to two weeks nonstop. The average Tour de France cyclist burns 100 calories a pound of weight daily, researchers say.

How the dogs maintain such a high level of caloric burn for an extended period without tapping into their reserves of fat and glycogen (and thus grinding to a halt like the rest of us) is what makes them “magical,” Davis says.

The magic of these sled dogs’ metabolisms is an excellent illustration of how breeding dogs to fulfill a working purpose rather than to meet an aesthetic standard can produce dogs with superior health.  Landrace breeds arise naturally in the environment.  Purpose-bred dogs come from breeding programs that focus on working characteristics instead of conformation.  An additional benefit of landrace and purpose-bred dogs from open, merit or informal lineages/registries is that because they are not selected from a limited pool of purebred ancestors to display a high degree of “breed type”, a much greater degree of genetic variability typically exist within these groups.

The Alaskan Huskies most commonly used as sled dogs are purpose-bred mixed breed dogs.  They are are descendents of the original northern sled dogs used by the native peoples that have been interbred with dogs brought north by settlers, gold miners, and fur trappers over the last 150 years.  The dogs are characterized by a high degree of genetic diversity.  It will be interesting to see how this factors into the study.