The objective of feeding any dog is to provide the best possible nutrition to ensure appropriate body condition is maintained whilst supporting the dog’s lifestyle and age. Working dogs, however, have higher energy needs than the average pet dog. Energy requirements (and the fuel which supplies the energy) will differ, depending upon the type of work the dog is undertaking.
Carbohydrates and fats are the key nutrients that supply energy to the body. For activities that do not require extreme bursts of energy – but need sustained energy over a prolonged period (for example sled dogs travelling around 100 miles per day) – fat is the crucial source of energy. Aerobic metabolism provides the fuel for this type of low intensity exercise. In contrast, activity requiring high intensity energy bursts for a relatively short period of time (for example racing greyhounds) is fuelled by anaerobic metabolism which is dependent on carbohydrate as its source of fuel.
Free fatty acids provide the energy for low intensity, prolonged aerobic exercise, but muscle glycogen (the storage form of carbohydrate) becomes the preferred source of energy for short bursts of high intensity anaerobic exercise. Between 70 and 90% of energy required for prolonged work is supplied from fat – and very little from carbohydrate – metabolism. In fact, if the body relies on carbohydrate as a major source of energy for sustained work the increase in anaerobic metabolism of muscle glycogen leads to lactic acid build up and the potential for exertional rhabdomyolysis (often known as tying up). Reduction in muscle glycogen leads to increased protein degradation in skeletal muscle, which may increase the risk of injury. Glycogen depletion can be resolved by providing carbohydrate supplementation immediately after exercise.
That isn’t to say that endurance work only relies on fats for energy: carbohydrate is still important. Carbohydrate is needed to enable the metabolism of free fatty acids required for aerobic exercise (for example when the body is under intense stress and requires a short burst of energy when working over difficult terrain).
Strenuous exercise may lead to oxidative damage of cells and tissues, and, in conjunction with a high fat diet, may result in increased fatty acid oxidation. Thus, a working-dog diet may benefit from increased levels of antioxidants such as Vitamin E and beta-carotene.
Pre-conditioning training is important when looking at olfactory ability as there is evidence that high levels of saturated fatty acids may negatively affect a dog’s olfactory system by modifying the nasal epithelium, reducing the ability to detect odours in low concentrations. It would appear, however, that if dogs are trained to detect low concentrations prior to introducing an energy-dense diet, their olfactory acuity is unchanged. It is interesting to note that when working dogs are pre-conditioned to the types of exercise they are expected to carry out, then the body and metabolic pathways become much more efficient in the use of energy sources.
Working dogs, just like human athletes, have increased blood volume and red blood cell mass in addition to a general increase in tissue mass. All these changes require an increased amount of protein which can only be derived from the diet. During exercise a small amount of energy (around 10%) is derived from the metabolism of certain amino acids, which adds to the need for increased levels in the diet to help prevent injury and tissue loss.
An energy-dense, protein-rich diet will increase urinary output and may lead to dehydration and potential electrolyte loss (sodium, potassium and chloride). Therefore, the working dog requires electrolyte supplementation and increased water intake. Cool water is more palatable and much more effective in cooling the body, and working dogs should be able to have frequent but small amounts of water throughout the period of exercise.
Weather can have a significant effect on the energy requirements of the working dog. In extremely cold weather the body requires more energy to maintain a normal body temperature. Surprisingly, in hot weather the body uses energy to cool the body temperature and as appetite is reduced in very hot/humid environments, working dogs should be fed a diet which is energy and nutrient dense to compensate for the reduction in food intake.
In conclusion, the physical and mental pressures of the working dog mean that his nutritional requirements are significantly different to those of the pet dog. The working dog requires an ‘energy dense’ diet. Foods containing lower levels of energy-supplying nutrients would have to be fed in huge amounts to meet the energy requirements of working dogs, resulting in decreased digestibility along with increased volume of stools. The capacity of the stomach is limited and, therefore, the increase in energy levels cannot be achieved by simply feeding more of a standard diet. A working-dog diet needs to be energy dense and contain high quality sources of fat, carbohydrate and increased protein content to ensure all the necessary amino acids are available to the body along with increased levels of crucial vitamins and minerals.