Have a look at your bag of dog food, and find the nutrition analysis. It will give you a figure for metabolisable energy, expressed in kilojoules or calories. Some ingredients, such as fiber, do add to the energy content of the food, but it’s not easy for your dog to digest. This means that it’s not readily available for your dog. Metabolisable energy is the amount of energy in your dog’s food that he can actually use. Dogs who run need more metabolisable energy than a sedentary dog.
Dog food manufacturers have recognised this and have started producing a range of foods for active dogs. These foods have higher levels of metabolisable energy, and may have higher protein levels, because your dog’s needs have increased, but his stomach capacity hasn’t. These foods may also have increased protein levels to help repair any micro-damage to muscles associated with strenuous exercise.
When you run, most of your energy needs come from carbohydrate metabolism. That’s not the case in your dog, who gets almost 90% of his energy for endurance from fat metabolism. There is some carbohydrate used for energy production in dogs. It is converted to glucose and then stored inside muscle cells in the form of glycogen. It is used for short bursts of exercise, and is used up very quickly.
You may have heard of human athletes “carbo loading” before an event, where they eat lots of pasta and potatoes to maximise the glycogen in their muscles. This has been tried in dogs, and it doesn’t work. There is an increase in muscle glycogen if you “carbo load” your dog, but it is also used up quicker so there is no real benefit. When glycogen is used to produce energy, a by product is lactic acid. Higher levels of muscle glycogen associated with carbo loading dogs means higher levels of lactic acid are produced, and this causes sore muscles.
There are three main sources of energy for your dog when he starts to run.
1. Inside the muscle cells, molecules of ATP and CP are broken down to produce energy. The energy is produced instantaneously but is used up in only one or two seconds. This energy powers that first enthusiastic jump at the start.
2. When this energy is used, your dog starts using up glucose and glycogen stores to keep his muscles going. This energy source can meet his needs for up to a few minutes. Think of an agility run or a flyball race – glycogen is most likely the source of the energy for these few fast minutes.
3. For longer events, such as the 5km, 10km and longer runs that we do with our dogs, they rely predominantly on fats for their energy needs. The sled dogs who race in the Iditarod race in Alaska have a diet that is around 70% fat.
An ideal diet for an endurance dog should have protein levels up to 30%, and fat content up to 50%. Feed him to condition, so if he’s a bit lean, give him more to eat. If he’s a bit too curvaceous around the middle, cut back on his food intake.