Canines differ from humans in many ways, and this is also true when it comes to how they exercise. While humans preferentially use carbs to produce energy when exercising at submaximal intensity, dogs’ metabolism is different: fat is the preferred fuel in their situation.
This explains you why nutritional strategies used for human athletes might not work in their canine counterparts.
Let’s take an example: you probably have heard of something called “carbohydrate loading”, or “carboloading” in human athletes: the concept is to eat a high amount of carbs before the athletic event so that you will have enough carbs’ reserves to fuel the effort.
Since dogs mainly run on fat and will therefore use their fat reserves, you understand why focusing on this strategy in canines athletes is no worth. In fact, this has even been studied in sled dogs. In an often referenced study (Kronfeld, 1973), a dog team that was fed with high carb diet performed poorly and developed a stiff gait while racing. When the dogs were changed to a diet containing increased levels of fat and protein, performance improved, and lameness resolved.
Since dogs preferentially run on fat, fat content on the diet can directly affect their performance.As you can see on the graph here, dogs that were fed with a high fat diet were able to run a longer distance and for a longer period before reaching exhaustion.