As in humans and horses, intense work and competition cause a specific energy expenditure in dogs, as well as physiological and psychological stress. But in dogs, unlike in the other species, the aspects of size and build come into play. These aspects give rise to nutritional specifics that must be considered in a dog's diet.
Nutritional adaptation is therefore necessary and must take into consideration quantitative and qualitative energy needs associated with muscular work, and also modifications in nutritional requirements based on a dog's build and stress level. Generally speaking, food formulated for sporting or working dogs should:
- provide an optimal quality of energy in adequate amounts;
- minimize the volume and weight of the intestinal bolus as much as possible (highly digestible and highly concentrated foods);
- help keep the animal properly hydrated;
- take into account the dog's body shape;
- possibly have a buffer effect on the metabolic acidification that can be caused by work;
- help maximize results of other ergogenic activities (training, etc.);
- fill physiological voids created by stress;
- be a true preventive factor for effort-related gastrointestinal problems.
It should also respect the animal's particular body type through a scientifically-based "mini," "medium," or "maxi" approach.
Quantitative changes in energy requirements
The daily energy requirements of a working dog are certainly higher than those for the maintenance diet of the same dog, but many variables are involved in determining the exact difference, which can sometimes be difficult to predict. Every trainer should aim primarily at maintaining the dog's proper weight by weighing the dog each week and adapting the amount of food administered accordingly.
A certain amount of data has helped define this approach for the very different cases of the racing Greyhound and the sled dog.
For Greyhounds, the strict energy requirement generated by a single race of under 30 seconds can be estimated by calculating the oxygen debt incurred, giving a result of approximately 75 kcal.
Another simulation borrowed from humans shows that for a given effort, the energy expenditure linked to movement is independent of speed for non-aerodynamic forces and dependent on speed squared for air resistance. This includes the energy required for initial acceleration, in which the dog's body moves from an initial speed of zero to racing speed. A Greyhound participating in a 480-meter race (Å 1/3 mile) at a speed of 17 meters (56 feet) per second expends approximately 70 kcal of energy in this example, which is quite close to our calculation and represents about 4% of the maintenance energy requirement.
Modification of hematocrit in relation to the quantity of proteins in the ration: case of the Husky in long distance race
Still, other factors that will affect the animal's energy requirements must be added to this theoretical approach:
– The number of races per day: If one race represents 4 to 5% of the maintenance energy requirement (approximately 1,800 kcal for a dog weighing 30 kg, based on 132 kcal ME/ kgO.75), two or even three races per day (as is the case for UICL races), combined with being placed in the starting box, will clearly increase the animal's energy requirements;
– Climatic conditions: A drop in the ambient temperature from 15° C to 8° C (27 to 14°F) causes a 25% increase in the metabolizable energy requirement for dogs. In warm climates, glycogen reserves appear to be more rapidly depleted in the body during work, given the considerable energy required for thermoregulation.
Thus, for a given dog and a given amount of effort (a racing Greyhound), the energy requirement will be in the range of 150 to 190 kcal per kilogram of metabolic weight (weightO.75).
Sled dogs have very different energy requirements than other sporting dogs. First, their maintenance level requirement is lower at equal weights, particularly for the Siberian Husky (10 to 110 kcal of metabolizable energy per kg O.75). The reasons for this are a higher metabolic energy efficiency, reduced thermoregulation expenditures because of the thermal insulation of the animal's coat, and the breed's body temperature, which is slightly lower than the norm.
Particularly detailed scientific research has been conducted on these dogs, given their irrefutable value as an example of extreme endurance effort. Double-marked water (with deuterium and tritium) has been used to determine the exact daily energy requirements of sled dogs in various racing conditions. In an "Iditarod"-type race day (approximately 200 km [125 miles] covered at a temperature of –35° C[-63°F]), this figure exceeds 11,000 kcal (approximately ten times the dog's maintenance requirement!). In a training or racing situation, the requirement depends on the type of effort, the length of effort, and the ambient temperature, as summarized in the attached table.
For other dogs, generally speaking, one hour of work leads to an increase of about 10% in the base energy requirement. This may mean increasing the energy ingested by 40 or 50% for a "day" of work or sport.
In fact, the vast majority of canine sports fall somewhere between the two extremes of racing Greyhounds and sled dogs. Agility, for example, is closer to the brief effort exerted by Greyhounds: 30 to 60 seconds of racing and obstacles over a distance of 100 to 200 meters (328 to 656 feet), repeated five or six times in one day. Ring events are also a series of brief exercises, but with a steadier rhythm over a longer period of time. With these other dogs, variations in ambient temperature seem to have a greater impact on the energy requirement than for sled dogs, whose "thermal neutrality zone" appears to be broader.
Sled dogs have very different energy requirements than other sporting dogs. First, their maintenance level requirement is lower at equal weights, particularly for the Siberian Husky (10 to 110 kcal of metabolizable energy per kg O.75). The reasons for this are a higher metabolic energy efficiency, reduced thermoregulation expenditures because of the thermal insulation of the animal's coat, and the breed's body temperature, which is slightly lower than the norm.
