PART 1: CANINE PERFORMANCE NUTRITION Justin Shmalberg, DVM, Diplomate ACVN University of Florida
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ACVN NUTRITION NOTES PEER REVIEWED Canine Performance & Rehabilitative Nutrition PART 1: CANINE PERFORMANCE NUTRITION Justin Shmalberg, DVM, Diplomate ACVN University of Florida ogs frequently engage in performance-based compet- Sprinting greyhounds, for example, require only about itive and recreational activities, ranging from flyball 10% more calories on race day compared with nonrac- Dto sled pulling to agility, and nutrition is increasingly ing active dogs.1 used to maximize an animal’s potential and stamina. Each • Huskies pulling sleds in cold weather over extended dis- canine activity has unique requirements for performance, tances require up to 8× normal energy requirements.1 which influence the caloric requirements and metabolism of individual animals. Calories Based on Exercise Duration Modification of feeding can, therefore, affect a dog’s Many canine sports require a consistent amount of exer- adaptation to such events. An expanding body of evidence cise from participants. suggests best practices for dietary modification in these dogs, and practitioners should be prepared to discuss the growing field of performance nutrition with interested The American College of Veterinary Nutrition owners. (acvn.org) and Today’s Veterinary Practice (tvpjournal.com) are delighted to bring you DOES EVERY CANINE “ATHLETE” NEED MORE the Nutrition Notes column, which provides the highest quality, cutting-edge information CALORIES? on companion animal nutrition, provided by the Calories provide the fuel for work. The normal activity of ACVN’s foremost nutrition specialists. 1 most pet dogs requires: The primary objectives of the ACVN are to: (90–110) × (ideal body weight in kg)0.75 = kcal Q 24 H • Advance the specialty area of veterinary nutrition • Increase the competence of those practicing in Additional activity requires more calorie expenditure. this field Veterinarians have frequently multiplied the resting energy • Establish requirements for certification in requirement by a factor to account for the activity level of veterinary nutrition a dog.2 However, the increases in energy expenditure by • Encourage continuing education for both working dogs are directly related to the distance traveled specialists and general practitioners during that work. • Promote evidence-based research • Enhance dissemination of the latest veterinary Calories Based on Distance nutrition knowledge. Studies suggest that running dogs require about 1.1 kcal/ The ACVN achieves these objectives in many ways, including designating specialists in animal kg per km traveled.1 nutrition, providing continuing education through • Dogs with longer limbs require less energy for trotting several media, supporting veterinary nutrition than those with short legs (0.6 versus 1.3 kcal/kg per residency programs, and offering a wide array of 3 km). resources related to veterinary nutrition, such as • Dogs traveling short distances, therefore, require fewer this column. calories than similar dogs traveling greater distances. 72 today’s Veterinary Practice November/December 2014 tvpjournal.com ACVN NUTRITION NOTES | CONVERTING CALORIES TO WORK TABLE 1. Expected Energy Requirements of The Role of Muscles Selected Canine Sports Muscles allow dogs to perform activity, and muscle LOW HIGH MODERATE fibers are generally classified as type I (slow twitch) (< 25% increase) (> 100% increase) or type II (fast twitch). Type I fibers contain lower amounts of myosin Agility Bikejoring Bikejoring adenosine triphosphatase compared with type II Coursing (2–10 miles) (> 10 miles) fibers; this difference is responsible for the slower Disc dog Carting Carting contraction observed in type I fibers.1 Dock jumping (2–10 miles) (> 10 miles) Type II fibers are subdivided into: Earthdog Field trials Sled dog racing • Type IIa fibers, which aerobically metabolize fat Flyball Herding (> 10 miles) CANINE PERFORMANCE NUTRITION or glucose and are much more fatigue resistant Greyhound racing Hunting than type IIb fibers Weight pulling • Type IIb fibers, which rely more on anaerobic glycolysis and, therefore, experience fatigue faster; however, these fibers permit explosive, • Short bursts of explosive activity—common in sports, but poorly sustained, bursts of activity. such as flyball or agility—require only small increases in While cats are known to have relatively equal calories. concentrations of type I, IIa, and IIb fibers, dogs • Conversely, endurance sports, such as field trials, hunt- possess fiber types that display substantial aerobic ing, and cart pulling, require more energy given the and anaerobic capacity, which had led some greater distance dogs must traverse. authors to question whether IIb fibers even exist Such information can be used to classify canine sports 1,5 in this species. These species-specific muscle according to expected energy requirements (Table 1).4 differences are consistent with evolutionary hunting In addition to distance and exercise duration, other strategies. Dogs are built for endurance hunting; cats for stalking and short chases.6 factors, such as thermal stress, terrain or slope, and ambient temperature, should be considered. Fuel Sources for Muscles Duration of muscle activity determines the primary DIETS FOR PERFORMANCE DOGS fuel source used for contraction. The guaranteed analysis found on dog food packaging is • Adenosine triphosphate (ATP), in small the primary reference for owners, but is of little utility for amounts, is used rapidly at the onset of activity comparing pet foods. Instead, nutrients are best expressed but is quickly depleted. on a caloric basis, commonly related as the mass (g) of a • Adenosine diphosphate, with help from given nutrient per 1000 Calories (kcal). creatine phosphate, can be converted to ATP, but sustains activity only temporarily. This value can be estimated from the guaranteed analysis • Glucose is subsequently used for aerobic or by using a calculation method described in Beyond the anaerobic metabolism, and glycogen provides Guaranteed Analysis: Comparing Pet Foods, available reserves for moderate exercise. Short bursts at tvpjournal.com in the Resources section (see In-Clinic of explosive activity, known as supramaximal Materials). exercise, can be sustained only as long as Dietary modification for active dogs should be based on glycogen provides glucose for anaerobic the distance of activity, irrespective of the perceived inten- metabolism. sity (Figure), and dietary recommendations can be based on the type of activities in which a dog participates. Using Fat for Fuel As the distance and duration of exercise increase, dogs use fat as an aerobic fuel source. Short Distance Athletes Interestingly, dogs at rest also display higher rates • Most research published is based on racing greyhounds.1 of fat oxidation compared with other species. The normal body condition score for such sighthounds Therefore, fat likely has the most profound effect is 3 to 4 using a 9-point scale as opposed to 4 to 5 in on increasing stamina in dogs.1 other breeds. Dietary fat is more energy dense than protein and carbohydrate: protein and carbohydrate contain between 3.5 and 4 calories per gram, while fat contains 8.5 to 9 calories per gram. The range arises from the digestibility of the ingredients. This difference in energy density between fuels means that working dogs can be fed additional calories by increasing fat in the diet rather than the amount of food given. This must be done cautiously to avoid inadvertently creating relative nutrient deficiencies. Figure. Nutritional trade-offs in diet selection. tvpjournal.com November/December 2014 today’s Veterinary Practice 73 | ACVN NUTRITION NOTES • Anaerobic energy is used exclusively for the first several Dogs engaging in multiday activities may benefit from seconds, but 50% of the energy required is obtained aero- post-exercise carbohydrate administration to facilitate bically in the first minute of a race.1,7 glycogen repletion.11 • Carbohydrate is used as a primary fuel, and modest increases in dietary carbohydrate may confer a small ben- WATER & ELECTROLYTE REQUIREMENTS DURING efit. The recommended carbohydrate amount is 105 to EXERCISE 135 g/1000 kcal.8,9 Commercial diets range from minimal Owners of working dogs understand that hydration is amounts (< 5 g/1000 kcal) in some canned diets to 150 critical to safe and maximal performance. Veterinarians g/1000 kcal in low-protein, low-fat, high-carbohydrate dry working with athletic dogs may encounter inquiries about diets, with an average of around 100 g/1000 kcal in dry the best ways to rehydrate animals after exercise. foods. Carbohydrates used in pet foods are often com- plex, and simple sugars are only infrequently used in per- Water Requirements formance dogs for post-exercise glycogen repletion when • Sedentary dogs require 0.6 to 1 mL of water per calo- several runs or trials of intense activity are expected. rie Q 24 H.1 This approximates 50 to 100 mL/kg/day, • Fat oxidation also occurs; therefore, dietary fat should be with smaller dogs requiring more water per kg of body moderate (> 30 g/1000 kcal). weight. • Pre-race fasting (> 8 hours) or caloric restriction may • Dogs continue to consume water even if dietary mois- improve performance due to reduced fecal mass.1 ture is very high, and water intake rises with increases • Most commercial diets for adult maintenance, whether in plasma sodium and urea. dry, canned, or frozen, fulfill the nutritional recommen- • Temperature, duration of exercise, and efficiency of dations for