by Leaddog » Wed Jan 19, 2011 3:10 pm
Calorie burn depends on the distance. In rough numbers, the dogs require about 2000 cal/day to simply exist. Regular household dogs need a bit less because they are not having to maintain body temperature in the cold and they don't have as much muscle (muscle maintenance is energy-intensive, even when you are not using them). Over and above that, figure about 60 calories/mile for the average-sized dog, regardless of whether it is racing or training. The dogs are not toting around a bunch of reserve for the same reason you don't see triathletes or competitive cyclists with excess body fat or really bulky muscle - it is simply weight that needs to be moved. The downside, though, is that there is always the possibility of an interruption in the caloric intake, so SOME reserve is needed to keep from lingering too close to the edge of the proverbial cliff. Factor in the distances between drop bags in the average race, and you can see that they must walk a fine line.
Calories are calories, regardless of the species, but to put it into perspective, the average Tour de France cyclist burns about 8000-9000 calories per day, but weighs 3 times the average sled dog.
The percentage of the diet that is fat is going to vary widely between mushers, and even between days for a single musher, depending on what is being fed. On a caloric basis, the diets tend to be in the neighborhood of 60% of the calories from fat. Certain snacks (like pure rendered fat) can be higher, others (like salmon) are lower. Fat is sort of the universal source of fuel the same way certain blood types are universal donors - just about anything we eat (fat, carbs, protein) can be turned into fat by our livers. The reverse is not true, though. The primary advantages of directly feeding fat are: if that is what they are going to burn anyway, it is more efficient and less stress on the liver; it is the most dense form of energy, so you can get it into the dog in large caloric amounts without overfilling the dogs's stomach; and it is very palatable so that even if the dog is tired and in a bad mood, they will eat it. The downside is that SOME protein and carb are required, and the diets that are very high in fat tend to have problems with storage (getting rancid, getting slimy, kibble breaking down into paste).