Nutrition and the canine athlete (Proceedings)

People have spent much time and energy over the years molding dogs into various shapes to suit our needs; The Illustrated Encyclopedia of Dog Breeds lists 91 hound breeds, 43 working breeds, 44 herding breeds, 49 gun dogs and 31 terrier breeds. Due to our changing life style, many of these breeds are no longer needed for what they were bred. These breeds still contain the genetic make-up for their original activities; this means that many of our companions have much more energy than is needed for a couch potato.

Working dogs are still found in many areas though. The federal, local and state governments employes dogs in areas of national defense, customs service and border patrol. Dogs are trained for service animals for the deaf and blind as well as the physically disabled. They are also still used for hunting, racing, endurance sled pulling and other athletic competitions. Canine agility competitions, Frisbee competitions, and herding competitions are found in many parts of our country. These provide a wonderful opportunity for man and dog to work together again as they were originally trained without having to maintain a herd of sheep!

Just like people who are athletes, training and nutrition can play a major role in the canine athletes success. But nutrition cannot overcome deficits in genetics and training. Matching nutrition to exercise type allows a canine athlete to perform to its genetic potential and level of training. In general, all working dogs have increased energy requirements over those of an adult dog during time of normal activity. The type of work being done and the intensity of work may require modifications in the nutrient composition of the food and the feeding schedule.

The work performed by most intermediate athletes (hunting dogs, field trials, Frisbee trials, Agility, Service work, Police work, Search and rescue, livestock management and exercise with people) resembles that done by endurance athletes (sled pulling), but is of shorter duration. The muscle-fiber type profile of intermediate athletes should resemble that of an endurance athlete over that of a sprint athlete (sight hounds). In general, endurance athletes have an increased number of well-developed slow-twitch fiber muscles; athletes involved in high speed sprinting have increased numbers of fast-twitch muscles. Slow-twitch muscles have a higher capacity for aerobic metabolism, meaning that they primarily use fat in the form of free fatty acids for energy. Fast-twitch muscles can use both aerobic and anaerobic pathways in that they can use both carbohydrates in the form of glycogen and glucose for immediate energy and fat for longer term energy use.

Exercise requires transfer of chemical energy into physical work. ATP (adenosine triphosphate) is the sole source of energy for muscle contraction. ATP is formed from metabolic fuels stored in muscle (endogenous) and from other body stores (exogenous). The energy is converted to ATP using either aerobic pathways using oxygen, or anaerobic pathways that can work without oxygen. The proportion of each pathway used is determined by duration and intensity of exercise, conditioning and nutritional status of the animal.

Training and conditioning results in adaptive physiological changes that facilitate efficient delivery of oxygen and other nutrients to the working muscle. Some of these changes include increased blood volume, increased red blood cell mass, increased capillary density, increased mitochondrial volume, increased activity and total mass of metabolic enzymes.

Fats

The two primary fuels used by the body for working muscles are muscle glycogen and free fatty acids. An intermediate athlete would receive ~70-90% of their energy from fat metabolism, and only a small amount from carbohydrate metabolism. Dogs rely more heavily on free fatty acids for energy generation at all exercise levels than do people. Feeding a higher fat diet to endurance and intermediate trained athletes prepares the muscles to efficiently mobilize and use free fatty acids for energy. It also exerts a glycogen sparing effect that can help prolong glycogen use during work. By increasing dietary fat concentration you can increase the energy intake and encourage stressed dogs to increase food intake due to the increased palatability of fat in the diet. Increased dietary fat levels may also enhance free fatty acid availability.

Carbohydrate

Provided sufficient gluconeogenic precursors are available in the diet, no dietary requirements for carbohydrates exist except during gestation and neonatal development. Gluconeogenesis (formation of glucose from non-carbohydrate sources) is done by the liver and kidneys using glycerol, lactate and glucogenic amino acids. Adipose tissue supplies glycerol for glucose production (breaking down triglycerides) and fatty acids for oxidation to supply energy, whereas muscle catabolism releases glucogenic amino acids, lactic acid and pyruvate for glucose production by the liver.

Carbohydrates fed to athletes should be highly digestible to decrease fecal bulk in the colon. Excessive amounts of undigested carbohydrates reaching the colon can increase water loss through the stool, increase colonic gas production and increase overall fecal bulk and therefore add unneeded weight.

Protein

Endurance training results in increased protein needs through increased protein synthesis (anabolism-the building up of muscle) and protein degradation (catabolism-the breaking down of muscle). Catabolism is only a small portion of the overall protein needs the primary use is anabolism. Increased tissue mass associated with training must be supplied by increased protein in the diet. (2) Amino acids are used in the formation of new muscle and repair damage to muscle and connective tissue during intensive conditioning; exercise increases the animo acid catabolism.

Amino acids provide ~5-15% of the energy used during exercise; most of this energy comes from the branched-chain amino acids (leucine, isoleucine and valine). All of these are essential amino acids and cannot be synthesized from other amino acids; they must be included in the diet. The "biologic value" of a protein is an indicator of the amount of essential amino acids found in that product. Muscle and organ meat based proteins have the highest level of essential amino acids, and are also the most digestible and most bioavailable.

Excessive protein intake may predispose an athlete to increased amino acid catabolism. Amino acids are not stored as proteins in the body but are deaminated (broken down) to ketoacids. These ketoacids are either oxidized for energy or converted to fatty acids and/or glucose and stored as adipose tissue (fat) or glycogen. The diet fed should supply adequate calories as fat and carbohydrate so that the protein fed can be used primarily for tissue synthesis and not for energy.

Water

Water is used as a solvent for biological solutes, it acts as a transport medium for nutrients, wastes and heat, absorbs physical shock and lubricates various internal and external surfaces. Heat is the primary byproduct of muscle contraction and the respiratory tract through panting is responsible for dissipation of this heat. Because evaporative heat loss is the primary way dogs dissipate heat, ensuring adequate hydration is crucial for the maintenance of normal body temperature. Depending on the type of work done and environmental conditions, water losses can increase by 10-20 times normal during exercise. Even mild dehydration can lead to decreased performance, decreased strength and hyperthermia. Water should be offered in small amounts frequently throughout the exercise period. If an insufficient amount is consumed, the dog might benefit by having water added to its food.

Supplements

Many breeders, exhibitors and trainers believe stressed dogs must also receive supplements of certain vitamins and minerals. There is no evidence to suggest that working dogs have increased requirements of these nutrients. If a diet is nutritionally balanced and the dog is consuming enough to meet its energy requirements during work, then additional supplements should not be necessary.

Diet Requirements

A diet needs to be highly digestible to limit the total volume of food consumed at each meal. Some maintenance diets may supply enough energy if consumed in large enough quantities, but may become bulk limiting and thereby limit performance in hard working dogs (too much stool production due to low digestibility).

An ideal diet would provide increased levels of high quality protein to meet anabolic requirements and enough non-protein energy nutrients (fats and carbohydrates) to meet energy requirements. By doing this, the diet provides sufficient calories with fat to limit the use of amino acids for energy leaving them available for muscle repair and replacement.

The food needs to be calorically dense and palatable, highly digestible and practical, so that the dog can physically consume enough to meet their caloric requirements. The price of the food, the form it is available in, storage conditions required and number of animals being fed also needs to be taken into account. What may be practical for l dog may be impractical for a kennel of 15 dogs.

Diet Considerations

Daily energy requirements (DER) can be highly variable and are directly related to the amount of work being done and the condition and training of the dog. Ambient temperature, psychological stress and geography are all environmental factors that may influence nutritional needs of the canine athlete. Of these ambient temperature can exert the greatest effect; with increased environmental temperature you get increased work and increased water loss. Lower environmental temperature increases energy expenditure for thermogenesis; this may be as much as a 50% increase over DER.

Stress in the form of intense physical exertion, weather extremes and psychological strain may negatively affect food intake, and an adequate amount of energy may not be available for the work required. Geographical factors such as elevation above sea level and changing elevations throughout a course as well as working in sand or tall grass may increase the workload and therefor energy expenditure.

Diet Calculations

The amount of energy required depends on the total work done: intensity × duration × frequency. DER (daily energy requirements) is ~ 1.6 × RER (resting energy requirements) for the average canine athlete. Sprinters may require 1.6-2 × RER and endurance or other high-end athletes may require 2-5 × RER.

Resting energy requirements can either be figured using 70 × body weight in kilograms (0.75 power), or 70 + (30 × body weight in kilograms). From there you can calculate the DER. Maintenance is typically 1.0-1.6 × RER depending on activity.

Feeding Plan

Look at where the dog is housed (inside/outdoors), medications they may be taking, dietary history; amount fed, type of food fed and timing of meals in relation to exercise/training and the nutrient profile of the diet, exercise and training history (amount of exercise done, frequency and performance of exercise).

Compare the current diets key nutritional factors, determine the amount to be fed and the timing of the meals, estimate energy expenditure using body condition scoring and exercise level.

Timing of meals is important to allow the most availability of nutrients to the athlete. Ideally 1 meal at least 4 hours before exercise, l meal within 2 hours after exercise and if necessary due to the duration of exercise small amounts during. The largest meal should be given post exercise. It is also very important to allow access to plenty of fresh clean water to prevent dehydration.

Reassess your plan based on body condition scoring, weight, hydration and performance. Adjust as needed to get the results that you want from your canine athlete.

Recommended Caloric distribution for Canine Athletes

      Calories from protein: 30-35% ME

      Calories from fat: 50-65% ME

      Calories from carbohydrate: 10-15% ME

Comparing products using ME gives a better idea of caloric distribution, and allows you to accurately compare canned and dry diets. This does not take into account digestibility.

It is also important when comparing foods to see if feeding trials have been done on the product and look at digestibility, if given. If you chose a food that has not had feeding trials done by the manufacturer, than you are doing the feeding trials for them.

Adapted from a table in Small Animal Clinical Nutrition. This list represents products with the largest market share and for which published information is available. Values are expressed on percentage of metabolizable energy.

References

Toll PW, Reynolds AJ. The Canine Athlete. In Hand MS, Thatcher CD, Remillard RL, Roudebush P (eds) Small Animal Clinical Nutrition. Fourth Edition. Marceline, Missouri: Walsworth Publishing, 2000: 261-283, 359

Case LC, Carey DP, Hirakawa DA, Daistotle L. Performance and Stress. In Canine and Feline Nitrition, A Resource for Companion Animal Professionals, Second Edition. St Louis, Missouri: Mosby Publishing, 2000: 259-273