The veterinary profession is currently witnessing an increased
demand from our clientele for information concerning performance of the
canine athlete. The expectations come as a result of the scientific advancements
in human sports medicine. If a pet owner is only interested in companionship,
minimal stress will be placed upon the pet's body. As the athletic demands
of the owner increase there is a proportional increase in the physical
demands placed upon the animal's body. A certain level of energy is needed
to maintain homeostasis, and additional energy is utilized during physical
activity. Designing the proper nutritional program begins by defining the
type of activity and then the level of activity the dog will be asked to
perform. Once the activity requirements are determined, the components
of the daily feeding regimen can be formulated. In addition, supplementation
can be utilized to address additional energy requirement needed by the
different activities. A professional and informed approach to feeding can
enhance performance and minimize problems that can result in poor performance.
Activity Type and Level
The body needs energy to maintain homeostasis, and additional energy
during physical activity. The maintenance energy requirement (MER) is defined
as the energy used by a moderately active adult dog in a thermoneutral
environment (MER=30 kcal/# for a 50+ pound dog). When the body performs
at a level greater than its normal daily routine there is a greater for
energy. Physical activities can be divided into two categories: strength/power
activities and endurance activities. Strength/power events are of short
duration (< 2 minutes) and are performed at intensities that are maximal
or supramaximal. Some events are intermediate, they are performed at varying
intensities for a duration of 2-4 minutes. Endurance events usually last
longer than four minutes and are performed at intensities < 90% of maximal
aerobic power (VO2 max). It is estimated that a dog hunting for one hour
utilizes 1.1 x MER, a full day of hunting utilizes 1.4-1.5 x MER, and a
sled dog pulling for one day uses 2-4 x MER.
The body utilizes three systems to provide energy for the body. The
type of activity defines which of the systems will be used. The immediate
energy source is from the one enzyme system. It provides energy for the
first five to twenty seconds. This system uses intracellular ATP, Creatine
Phosphate (CP), and the ADP/myokinase reaction to provide energy for increased
body activity. The glycolytic energy pathway provides energy from five
to twenty seconds up to two minutes. Energy comes from the anaerobic breakdown
of glucose. This is a more complicated form of energy production involving
multiple steps and enzymes. The third energy source is from oxidative metabolism.
It starts approximately two minutes after the start of the physical exercise.
It is the most complicated energy system. It can use various substrates
and is the most efficient energy system. Strength/power activities rely
heavily upon the one enzyme and the glycolytic energy systems, and endurance
activities rely upon the oxidative energy systems.
Nutritional Components
The three energy sources used by the body are carbohydrates, proteins,
and fats. Digestible carbohydrates are the sugars and the starches. Cellulose,
pectin, and gums are the carbohydrates that are termed fibers and are minimally
digestible. The simple sugars, called monosacharides, are glucose, fructose,
and galactose. These carbohydrates are in the smallest form and do not
need to broken down to be absorbed by the intestine. The disacharides are
sucrose, maltose, and lactose and are compounds composed of two of the
simple sugars. The starches are complex carbohydrates, polysaccharides,
that are long chains composed of the simple sugars. Disacharides and polysaccharides
need to be broken down enzymatically to be absorbed by the intestine. Carbohydrates
have an energy yield of 3.5 kcal per gram.
Protein is both an energy source an a source of amino acids. High-quality
animal source proteins proteins provide superior digestibility, amino acid
balances, and palatability. Exercise increases an athlete's protein requirement.
Exercise places excess demands upon the body which result in tissue disruption
and occasionally tissue damage. These tissues must be remodeled and repaired
which can result in an increased protein demand. This demand can be met
by increased protein ingestion. Protein can also be used for an energy
source with an energy yield of 3.5 kcal per gram.
Fat is used by the body for energy and can be used as a metabolic water
source. Fats are highly digestible, very palatable, and are an energy dense
nutritional ingredient. It has an energy yield of 8.5 kcal per gram. They
are also essential for the absorption of the fat soluble vitamins, A, D,
E, and K. Fat provides a source of metabolic water. Fat metabolism produces
107 g of water for every 100 grams of fat. Protein produces 40g water/100g
protein, and carbohydrate produces 55g water/100 g carbohydrate. Fatty
acid ratio can also help to reduce the production of inflammatory mediators
in canine skin, plasma, and neutrophils. Dietary omega-6:omega-3 fatty
acid ratios between 5:1 and 10:1 are optimum.
Vitamins and minerals are also very important in the canine athlete.
Some important vitamins are A, D, E, K, and the B-complex vitamins, especially
thiamin, niacin, and cyanocobolamine (B1, B3, and B12). Vitamin A plays
a role in ligament and tendon health. Vitamin D is important in maintaining
the calcium and phosphorus balance. Vitamin E is a very important anti-oxidant.
It acts to maintain cell membrane stability, which is very important in
dogs that use their olfactory senses, i.e. pointing breeds, detector dogs,
and search and rescue dogs. Vitamin K is important to maintain proper blood
conditions in the canine athlete. Thiamin helps to minimize the effects
of stress related to competition and performance. Niacin aids in carbohydrate
metabolism, and is required for red blood cell production. Cyanocobolamine
is essential for synthesis of protein and formation of red blood cells
and hemoglobin. Most vitamin needs are met with a normal high quality diet,
but in certain situations supplementation can be beneficial to performance.
Nutritional Program Design
Sprint athletes utilize the one enzyme system and the glycolytic energy
system. The duration of their activity does not last long enough to access
energy from the oxidative energy system. Their base diet should include
a high percentage of carbohydrates and protein. Some of these diets are
currently manufactured or carbohydrate sources can be added to a traditional
high protein diet. If the competition involves many repetitive sprints
or activities the body will at some point begin using energy from the oxidative
system. In these cases a better diet would include a balance of carbohydrates,
protein, and fat energy sources. The increase in fat content would provide
energy for the later activities.
Endurance athletes are much more dependent upon the oxidative energy
systems. These athletes would benefit from a higher percentage of fat in
their diet. Some manufactured diets are balanced in this way or a fat based
supplement can be added to their normal diet. When the body is burning
fat for its energy source it delays muscle glycogen depletion. This action
then delays the deleterious effects of fatigue. It has also been shown
that burning fat is metabolically cooler than burning protein. Minimizing
the increase in body temperature would be beneficial to dogs working in
endurance events. This is especially true for dogs working in warmer environments.
*** An important note is that it takes four to six weeks for the body
to condition itself to benefit from any diet alterations. This is especially
true when increasing the fat content. For example, the hunting dog must
begin adding the fat supplement at least four to six weeks prior to the
beginning of the hunting season. Also, to benefit from the diet change
at the beginning of the hunting season, a conditioning or training program
must begin at this same time the diet change is initiated to train the
body systems to utilize the supplement. ***
Supplementing with vitamins and minerals can enhance performance. Supplement
timing is the key factor when influencing performance. Simple sugar carbohydrates,
proper protein, combined with the applicable vitamins and minerals can
be given at key times around the event to benefit performance. These will
be discussed in greater detail in subsequent articles.
Summary
The veterinarian should discuss the expectations of the owner, and determine
exactly what demands are being placed upon their dog. Once the activities
are determined, a proper nutritional program can be designed to provide
the amount and type of energy that is needed to maximize performance.
