Muscle Physiology and Feeding the Performance/Working Dog

Exercise requires increased function of several organ systems and energy metabolic pathways. Dramatic changes take place within dogs to support exercise, and as a result, of exercise. Certainly, nutritional needs are affected by exercise. An understanding of exercise physiology is fundamental to assessing and
developing a feeding plan for canine athletes. The following review of exercise physiology relates particularly to nutrition of canine athletes. This discussion includes: 1) a review of muscle metabolism that outlines the energy needs of working muscles, substrate requirements and the by-products of energy metabolism, 2) exercise type and intensity, which determine the preferred metabolic substrates and therefore the nutrient profile, 3) some of the physiologic changes that occur during exercise and how they may affect nutrient needs and 4) the energy cost of running, which dictates dietary energy needs.
All of these factors are important to nutritional assessment of canine athletes and form the basis for a good feeding plan.

Muscle Metabolism

Muscle Fiber Types
Muscles are not homogeneous. They are composed of fibers with different contractile and metabolic characteristics. Muscle fibers are classified into two groups based on contractile properties and histochemical staining:Type I or slow twitch and Type II or fast twitch. Type I fibers have high oxidative capacity and
endurance. These fibers are smaller than Type II fibers and have high capillary density and high numbers of mitochondria. They are low in glycolytic ability and low in staining for myofibrillar ATPase, an enzyme associated with fast contraction and relaxation. Conversely, Type II fibers are high in myofibrillar
ATPase, larger, contain more glycolytic enzymes and have greater strength. In most species, Type II fibers can be further subdivided into Type IIa and Type IIb. Contraction characteristics are similar for Type IIa and Type IIb fibers, but Type IIa fibers have greater oxidative capacity than Type IIb fibers; the
latter are more fatigable. However, dogs and perhaps other members of their genus and subfamily, appear not to have classic Type IIb fibers but, instead, two other kinds of Type II fibers that are more oxidative (called Type IIDog and Type IIC). This fits with the general observation that dogs are tireless runners
The fiber composition varies between muscles and between individuals. High-power athletes such as racing greyhounds have a higher proportion of Type II fibers, whereas endurance athletes have a higher proportion of Type I fibers. Because the work performed by most intermediate athletes resembles that done by endurance athletes, but is of shorter duration, the muscle fiber-type profile of intermediate athletes should resemble that of endurance athletes more than that of sprint athletes. Muscle fiber type is a function of genetics and dictates the type of exercise for which an individual is best suited. However, some modification is possible through training. Endurance training increases the number and volume of mitochondria and increases capillary density in all fiber types
.
Muscle Energetics
Exercise requires the transfer of chemical energy into physical work. Chemical energy stored in high-energy phosphate bonds of adenosine triphosphate (ATP) is the sole source of energy for muscle contraction. ATP is cleaved to ADP during contraction. The amount of ATP used is proportional to the amount
of work performed (i.e., Fenn effect). ATP is vital not only for the events of contraction but also for relaxation and maintenance of important ion gradients.Normal excitability of nerve and muscle is due to an electrochemical gradient maintained by the sodium-potassium pump at the expense of
ATP. The calcium pump uses ATP to maintain a low concentration of calcium in the muscle cell in the relaxed state. An estimated one-third of the basal energy requirement is used to maintain electrolyte concentration gradients across cellular membranes Although ATP is the high-energy compound that cells use
as fuel to perform work, the energy required for exercise can ultimately come from a variety of sources. Because the concentration of ATP in muscle cells is relatively low in comparison to the cell’s need during exercise, ATP must be replenished from other fuel sources. These metabolic fuels are stored in muscle
(endogenous) and at other body sites (exogenous). The metabolism of these fuels occurs either with oxygen (aerobic) or without oxygen (anaerobic). The anaerobic pathways (i.e., the creatine phosphate shuttle and glycolysis) occur in the cytoplasm, whereas the aerobic pathways (i.e., complete oxidation of glucose, fatty acids and amino acids) take place in mitochondria. The proportion of each pathway used is determined by the duration and intensity of the task performed and by the conditioning and nutritional status of the animal. The concentration of ATP is tightly regulated, although it is rapidly consumed during exercise. Resting muscle cells have only enough ATP to fuel muscle contraction for a few seconds. If work continues beyond this point, ATP must be regenerated
from other metabolic fuels at a rate comparable to that at which it is being consumed. Creatine phosphate (Cr-P) is an endogenously stored fuel that muscles can rapidly convert to ATP. The Cr-P shuttle permits the maximum rate of ATP synthesis possible; however, this pathway can only support maximal efforts for five to 15 seconds because muscle Cr-P stores are very limited. Glucose is a versatile metabolic fuel that is stored endogenously as muscle glycogen and exogenously as glycogen in the liver and to a much smaller extent as free glucose in the blood. Glucose can be metabolized to regenerate ATP by both anaerobic
and aerobic pathways. Anaerobic metabolism of glucose (glycolysis) results in very rapid ATP production or high metabolic power, but only yields two ATP
per molecule of glucose.Aerobic metabolism, the complete oxi-dation of glucose to CO2 and water, regenerates ATP less rapidly, but results in a much greater yield (36 ATP per molecule of glucose). Because total body glucose stores (glycogen) are relatively small (1 to 2% of body weight), even aerobic metabolism of glucose cannot sustain exercise for extended periods of time. Fatty acids are stored in ample supply in adipose tissue and within muscle. They are the primary energy source for long-lasting exercise. Although small amounts of fatty acids are stored in muscle, this source may contribute up to 60% of the fatty acids oxidized during the first two to three hours of exercise. Amino acids are usually not a primary energy source for exercise. Oxidation of amino acids may contribute up to 5 to 15% of the energy used during exercise, depending on the intensity and duration of the task. Most of this energy comes from
the oxidation of the branched-chain amino acids leucine, isoleucine and valine. Most amino acids are structural or functional components
of proteins and the size of the labile amino acid pool is very small, making amino acids a less significant fuel source for exercise in most circumstances.
The proportion of energy substrates and metabolic pathways used during exercise depends on the intensity and duration of the exercise. As exercise intensity increases, the power output and the rate of energy metabolism must also increase. As exercise duration increases, total substrate availability and energy
yield become more important. High-power activities (e.g., sprinting) rely heavily on anaerobic metabolism, whereas more prolonged activities require the higher energy yield provided by oxidation of glucose and fatty acids. As the duration of exercise increases, oxidation of fatty acids becomes more important.

By-Products of Muscular Work

Heat is the primary by-product of muscle contraction; 75 to 80% of the energy used during muscular work is converted to heat. A 10-fold increase in metabolism results in a 10-fold increase in heat production. Unless the animal is working in a very cold environment, this heat is a by-product that must be removed (even some sled dogs overheat). In dogs, the respiratory tract is responsible for dissipating most of this heat. Normal body temperatures of dogs doing physical work are higher than their normal resting temperatures. During very intense exercise or exercise in hot environmental temperatures, heat production exceeds the ability of the respiratory tract to lose heat, increasing body temperature. The body temperature of racing greyhounds may increase more than 1°C (1.8°F) after
a 30-second race. Some breeds can have normal working temperatures up to 41.1°C (106°F) (Gillette, 2002). Some dogs can have normal working
temperatures up to 41.6°C (107°F). Because evaporative heat loss is the primary way dogs dissipate heat, ensuring adequate hydration is crucial for maintenance of normal body temperature. Metabolic acid is another by-product of energy metabolism that must be eliminated during and after exercise. Aerobic
metabolism generates ATP by combustion of carbohydrates and fats to CO2 and water. Lactate is the endpoint of anaerobic metabolism. Either way, acid is produced that must be eliminated in some way for exercise to continue. Muscle enzyme activity is highly pH sensitive. Therefore, if energy metabolism
and muscle contraction are to proceed optimally, muscle pH must be tightly regulated. Intracellular buffers can blunt some of the acute effects of increased concentrations of CO2 and lactate. However, elimination of organic acids from muscle cells is the primary strategy for avoiding deleterious decreases in muscle
HCO3 - + H+pH. Because it is a weak electrolyte, CO2 has less effect on pH than lactate (a strong salt of lactic acid) and is handled differently by the body. Assuming no other primary acid-base changes, CO2 and bicarbonate (HCO3-) increase in parallel because of the following relationship: CO2 + H2O
The CO2 load produced during exercise can be eliminated via two routes: 1) respiratory loss of CO2 (acute) and 2) renal excretion of HCO3- (long-term). The ability of the kidneys to respond acutely may be impaired because of decreased plasma volume and renal blood flow during exercise. The respiratory system responds very quickly by increasing ventilation to excrete excess CO2 (and excess heat).Aerobic exercise generally does not produce large acid-base changes, because the respiratory system can excrete CO2 as fast as it is produced. The acid-base consequences of anaerobic metabolism are more severe and less easily handled by the body. Lactate is the anionic form of a strong organic acid and does not participate in any dissociation equilibria. This means that lactate has a
greater effect on pH than CO2 and its acid-base effects must be ameliorated by other compensatory changes until it is metabolized. Lactate is oxidized for energy by muscle or converted back to glucose in the liver (Cori cycle).

Exercise Intensity and Duration
Energy and other nutrient requirements for canine athletes are determined by the intensity and duration of exercise. Exercise intensity can be described in a variety of ways depending on body weight and type of activity. Exercise intensity is a measure of work done per unit time. For dogs, the type of work done is
usually running and the amount of work done depends on body weight, distance traveled and changes in elevation. The amount of work done is directly proportional to the amount of energy used. Therefore, energy use describes work done. (CONTINUED BELOW)

 

(CONTINUED)For example, a 30-kg dog expends about 30 kcal to cover 1 km on a flat surface, regardless of how fast it walks or runs (minor differences may occur due to differences in efficiency of various gaits for running at a specific speed). Running speed (distance/time) is a measure of exercise intensity (work/time) or
power (energy/time). A direct relationship exists between running speed (km/hr) and energy use rate (kcal/hr or kJ/hr) for an individual of a given size. However, individuals of different sizes expend different amounts of energy to run the same speed, making running speed a poor measure for comparison of
workload between individuals of different sizes. Exercise physiologists have traditionally used oxygen consumption (VO2) as a measure of workload. The body only uses oxygen for combustion of substrates to produce energy. Each liter of oxygen consumed represents an energy expenditure expenditure of about 4.8 kcal or 20.1 kJ. Therefore, the VO2 indicates the rate of energy use, at least at submaximal exercise levels. At very high workloads, exercise intensity can be increased without a further increase in VO2. The workload at which this occurs is called maximal oxygen consumption (VO2 max). Exercise intensity is frequently expressed as a percentage of VO2 max in order to compare different types of activities for individuals of different size within a species and between species. Exercise intensity dictates the severity and types of physiologic changes associated with exercise, including substrate use, metabolic pathways and waste production. Low intensity exercise is up to 30% of VO2 max and is completely aerobic, using mostly fatty acids. Exercise intensities from 30 to 50% of VO2 max (moderate intensity) are still completely aerobic, but carbohydrates become an important energy substrate (carbohydrate threshold). At high-intensity exercise
(75 to 100% of VO2 max), anaerobic metabolism becomes important and lactate begins to accumulate in the blood. The anaerobic threshold is the workload at which lactate concentrations in the blood increase to 4 mmol/l or more. When working at exercise intensities at or above the anaerobic threshold, lactate in the blood begins to accumulate at an exponential rate, potentially limiting the duration of the exercise.Workloads above VO2 max are called either maximal or supramaximal, are highly dependent on anaerobic metabolism and result in large increases in blood lactate concentrations. Exercise intensity dictates metabolic pathways and substrate use. High-intensity activities (sprinting) depend on anaerobic metabolism of carbohydrate (glucose and glycogen), which is supported by high-carbohydrate foods. The severe acidemia produced by high-intensity activities underscores the need for adequate electrolyte and water intake. Endurance events that take place at low to moderate intensity for long periods are completely aerobic and rely mostly on oxidation of fatty acids. Thus, as exercise duration increases, the fat fraction of the food becomes more important to supply energy needs. Intermediate exercise (as performed by most canine athletes) is usually of low to moderate intensity, but may include some short periods of high-intensity work. Both fats and carbohydrates are important fuel sources in intermediate exercise.

Physiologic Changes Due to Activity

Anticipation
Anticipation to perform work can affect metabolism in dogs. Some dogs have significant blood parameter changes as a result of anticipation to perform
specific tasks. Some had a significant increase in serum calcium and total bilirubin and a significant decrease in serum glucose, total protein, cholesterol and insulin associated with anticipation. A regimen of physical conditioning had a significant affect on the anticipatory changes in foxhounds and sled dogs. The
effects of anticipation can play a role in a dog’s ability to perform selected activities

. Physiologic Changes Due to Exercise
The hallmark of exercise is increased metabolism. Many organ systems increase their activity, some by several-fold, whereas some systems decrease their function. The systemic changes that occur during exercise seem to be driven by the muscles’ need for substrates and removal of metabolic waste.Working
muscle metabolizes substrates (mostly fatty acids and glucose) to release energy stored in chemical bonds for contraction.The products of muscle metabolism are contraction, heat, CO2, NH3/NH4+, water, and in some cases, lactate. Muscle metabolism can increase more than 20-fold in dogs, depending on the intensity of the exercise. Likewise, cardiac output increases proportionally with the workload. Both stroke volume and heart rate increase. Blood is the transport
medium that carries oxygen and other substrates to the working muscle and removes by-products such as heat, CO2 and lactate. Increased function of the respiratory system (both increased rate and depth) supplies more oxygen and disposes of more CO2. Dogs and other mammals with contractile spleens can increase effective circulating blood volume and hematocrit by expelling red blood cells from the spleen before or during exercise. For example, racing greyhounds increase blood volume as much as 24% before racing, even in the face of a 10% shift of plasma volume to other fluid compartments. Probably as a result of both the plasma shift and splenic contraction, hematocrit can increase as much as 29%. Plasma volume decreases during exercise because of hydrostatic and osmotic forces. Increases in blood pressure during exercise cause a shift of fluid from the intravascular space to the interstitial compartment.
Muscle activity tends to increase intracellular osmotic pressure, encouraging fluid movement from the interstitial to the intracellular spaces. The kidneys conserve plasma volume losses during exercise. Decreases in plasma volume that decrease central venous pressure cause renal vasoconstriction and diminish glomerular filtration rate (GFR). Decreasing GFR will normally decrease urine output and thus diminish plasma volume losses. Increases in plasma osmotic concentration that occur during prolonged exercise also stimulate secretion of antidiuretic hormone (ADH), which conserves
plasma volume by stimulating production of a more concentrated urine. Exercise affects plasma volume and composition. Loss of fluid to the intracellular compartment increases the concentrations of plasma proteins, electrolytes and all other solutes in the extravascular compartment. Other primary plasma
changes that are needed to support increased muscle activity are a direct result of that activity. Glucose concentration may increase or decrease depending on the intensity and duration of exercise. The concentration of free fatty acids increases during prolonged exercise. At very high workloads, the partial
pressure of oxygen may fall dramatically. Acidemia is also common with maximum intensity exercise because of anaero-bic metabolism and accumulation of lactate in the blood. The important points from the above discussion are: 1) exercise increases metabolism and therefore increases the need for energy, 2) cardiovascular function increases and fluid shifts/losses occur during exercise-adequate water intake is important to support these needs and 3) transient changes also occur in the composition of blood that can influence the interpretation of results from blood samples drawn soon after exercise.

Energy Cost of Running

The energy cost of running depends on body size and distance traveled. As body size increases, the efficiency of running increases (i.e., larger animals use fewer kcal/kg to run the same distance).
History
In addition to the normal historical information that is usually obtained about a patient, the following information should be gathered from owners: environmental/housing data, medications, dietary history and exercise type, amount, frequency and performance. Detailed information should be gathered
about how the dog is housed, including: indoors or outdoors, size and type of housing, opportunity for spontaneous exercise, type of surfaces, number of dogs housed together and access to food and water. All medications used should be recorded, including drugs used to suppress estrus and drugs used to enhance performance. The dietary history should include all foods and supplements used. The amount fed, nutrient profile and timing of feeding in relation to exercise should be noted. The amount eaten should also be assessed (i.e., Does the dog have a normal appetite and is it actually consuming a reasonable amount?). In some cases, the composition of the overall diet (food plus supplements) may be complex and individual meals may vary in composition. It is also important to ascertain the duration of a particular feeding plan. Abrupt or frequent changes in food or feeding method may affect performance.

Exercise Type
Functionally, exercise can be divided into three types based on intensity and duration: 1) sprint-high-intensity physical activity that can be sustained less than two minutes, 2) intermediate-physical activity lasting a few minutes to a few hours and 3) endurance-physical activity that lasts many hours. These definitions are arbitrary and vague, but are useful for assessing and developing feeding plans. Most canine sprinters are sight hounds, racing greyhounds being the most notable example. Metabolically, weight-pull dogs might also fit into this category. Some racing sled dogs that participate in shorter, high-speed events are referred to as “sprinters.” However, they fit better in the intermediate or endurance categories from a metabolic and nutritional standpoint because their events may last several hours. Other breeds that engage in other activities also do considerable sprinting. However, because they compete multiple times per day, they too fit better in the intermediate category. Based on energy needs, most canine athletes participate in intermediate exercise activities. Most of these activities are of low to moderate intensity and last only a few hours. Intensity and duration of exercise vary widely within this category. For example, most guide dogs work at a low level of physical exertion for variable lengths of time throughout the day, whereas a search and rescue dog may work at a much higher level for many consecutive hours. Other dogs at the upper end of the intermediate exercise range can include foxhounds, coonhounds and other hunting dogs in the field. At times, they work at levels that are near the lower end of the energy requirement range for endurance dogs. Dogs that work at a
relatively high intensity level for many hours, such as racing sled dogs, have much greater energy requirements and are true endurance athletes.
Exercise amount can be quantified as hours per day or week. Frequency is how often the animal exercises: daily, weekly, weekends only or seasonally. Many hunting dogs only work hard on weekends during hunting season, whereas some livestock (CONTINUED BELOW)

 

(CONTINUED) dogs may work several hours daily. Canine athletes should be categorized as either “full-time” or “part-time” athletes.

Environmental Influences on Exercise

Ambient temperature and humidity, psychological stress and geography are environmental factors that may influence performance and nutritional needs of working and sporting dogs. Of these, ambient temperature and humidity exert the greatest effect. Hot temperatures result in increased work and water loss
(i.e., to excrete metabolic heat and maintain body temperature homeostasis). High humidity impairs evaporative cooling thus adding to the work of heat excretion. Cold temperatures without exercise increase the energy requirement for thermogenesis. For working dogs, cold environmental temperatures aid in
heat dissipation during exercise. Excitement or stress associated with some activities increases body temperature and respiration, leading to greater requirements for energy, water and perhaps electrolytes. Stress may also negatively affect food intake. Geographic factors such as high elevation,
changing elevation (running up and down hills), bodies of water (swimming) and the presence of sand or tall grass underfoot can increase workload.

Key Nutritional Factors

Water
Water is arguably the most essential of all nutrients. It is the solvent for nearly all biologic solutes and a transport medium for nutrients, wastes and heat. Water also absorbs physical shock and lubricates various internal and external body surfaces. Approximately two-thirds of the body’s weight is composed
of water. Total body water is divided into four major compartments. Approximately 62 to 64% of water is located within cells, 22% within interstitial spaces and 7% within the intravascular space in plasma. The remaining 7% is present as transcellular fluids such as vitreous and aqueous humor, cerebralspinal fluid,
F) (NRC, 2006). Exercise in very cold, dry environments also increases evaporative fluid losses. Significant fluid loss during exercise may impair performance. Even mild dehydration can limit exercise performance.Several studies indicate that hydration status is the single most important determinant of endurance capacity. There is currently much debate over the best strategy to maintain fluid and electrolyte balance in working dogs. Under most exercise situations, these athletes lose more water than electrolytes, causing a decrease in plasma volume and an increase in plasma osmolality. Efforts to return electrolyte values to normal should thus concentrate on water replacement. Ideally, fresh clean water should be available at all times.C (113joint fluid and digestive secretions. Osmotic, oncotic and hydrostatic pressures as well as the permeability characteristics of individual membranes direct fluid balance between compartments. Dietary water intake and metabolic water production (10 to 16 ml/100 kcal and 3 to 4 ml/g glycogen) on one hand and evaporative, urinary and fecal losses on the other maintain total body water balance. The fluid content of individual tissues and compartments changes with the onset of muscular activity. Cardiac output, partially a function of plasma volume, increases during exercise to meet the muscle’s heightened demand for nutrient delivery and waste removal. The increase in blood flow also helps dissipate the heat produced by working muscles. Only about 20 to 30% of the energy consumed within muscle cells during exercise produces work; the remaining 70 to 80% is converted into heat. This is about the same efficiency as a gasoline engine. This heat must be dissipated to prevent performance impairments and perhaps life-threatening increases in body temperature. During prolonged periods of exercise in warm and humid environments, heat dissipation leads to a decrease in total body water and plasma volume. Approximately 60% of the heat dissipated during exercise is lost through fluid evaporation from the upper respiratory tract.Water requirements essentially double in dogs when the ambient temperature reaches 45
There are occasions when such accommodations cannot be made due to the nature of the athletic event or the environmental conditions. Under these conditions, water should be offered at least three times a day and more often if possible. “Baiting” the water with a flavor enhancer such as meat juice
can encourage water intake.

Energy

Providing the right amount of energy from the right sources is central to feeding working and sporting dogs. Providing the correct amount of energy is determined by the food’s energy density and the amount fed. The energy density can limit the maximum possible caloric intake and a food’s overall digestibility. Additionally, the preferred source of energy (fat vs. carbohydrate) depends on exercise type. Energy for exercise comes from three nutrients: fat, carbohydrate and protein. Fats and carbohydrates are the primary energy substrates for exercise. Fat is the preferred substrate for longer duration exercise, whereas sprinters depend more on carbohydrate. Under most conditions, the energy contribution of protein during exercise is small however, its contribution will increase in fatigued dogs. Energy required depends on the intensity, duration and frequency of exercise. The amount of energy required for exercise
depends on total work done (intensity x duration x frequency). The preferred source of energy depends mostly on intensity. Greyhounds, even though they work at a very high intensity, have relatively low energy requirements because the duration of their events is so short and frequency is usually only a few times
each week. Generally, 1.6 to 2 x resting energy requirement (RER) is adequate for most sprint athletes.Note the daily energy requirement (DER) for most pet dogs is 1.2 to 1.4 x RER. Most pet dogs are minimally active. For activities of very short duration and high intensity, the energy substrate source is the main determinant of the nutrient profile. Foods for sprint athletes should be high in carbohydrate and lower in fat, with a resulting energy density lower than that
of many dog foods. Intensity, duration and frequency of exercise are variable for intermediate athletes; therefore, the energy requirement is highly variable. DER for these athletes ranges from 2 to 5 x RER. Foods with a higher fat content are typically fed to provide adequate dietary energy density. Endurance
athletes require more than 5 x RER. For activities of long duration, providing adequate energy is a major determinant in the choice of a nutrient profile for exercising dogs. Foods that arevery high in fat are required.

Fat

Fat provides approximately 8.5 kcal (36 kJ) of metabolizable energy (ME) per gram of dry matter (DM) or more than twice the amount provided by protein and carbohydrate. Because of these differences in caloric density, the only practical means of significantly increasing the energy density of a food is to
increase its fat concentration. Reasonable increases in fat usually also increase palatability. Energy density and palatability make dietary fat levels an important consideration in the formulation of foods for working and sporting dogs. Increasing dietary fat generally also increases a food’s digestibility because
fat tends to be more digestible than protein or carbohydrate. Also, when a greater quantity of a lower energy density food is eaten in an attempt to provide adequate calories, there is a more rapid rate of passage through the gastrointestinal (GI) tract, further reducing digestibility and energy intake. Ingesting adequate calories to meet daily energy expenditure is often a serious challenge for working dogs. In extreme cases, sled dogs in long-distance races expend from 6,000 to 10,000 kcal/day (25 to 42 MJ/day), in which case DM intake becomes a performance-limiting factor. Because the total daily DM intake is limited to about 3.5% of body weight,c the energy density of a food should be maximized. Under these circumstances, each nonessential gram of protein and carbohydrate ingested potentially robs the dog of 5 kcal (21 kJ). The calorie deficit is paid through mobilization of body fat stores. Overreliance on these depots may lead to catabolism of more functionally crucial energy sources, such as muscle and plasma proteins. In addition to its role as an energy store, adipose tissue
also functions as an insulator. Excessive adipose depletion may increase a dog’s cost of maintaining its body temperature, especially at rest in cold environments. Even under the less severe conditions of intermediate exercise, increased dietary fat levels provide needed energy and other valuable benefits. Fatigue and dehydration may decrease appetite. Increasing dietary fat concentration increases energy intake and encourages stressed dogs to ingest more food
because the higher fat content improves palatability. Feeding high levels of fat can positively affect endurance. Training may elevate the carbohydrate threshold, thus increasing the proportion of energy supplied by free fatty acid (FFA) oxidation at all but the highest intensities of exercise. Increasing
dietary fat concentration may augment this process by enhancing FFA availability. Working dogs fed high-fat foods have higher circulating levels of FFA at rest and respond to exercise stimuli by releasing more FFA than those fed isocaloric amounts of a high-carbohydrate food. This difference in FFA availability may be related to the decreased resting plasma concentration of insulin in animals fed high-fat foods, and the induction of key lipolytic enzymes. The effect of food on insulin levels has also been demonstrated in well-trained human athletes People eating high-fat foods had significantly lower resting insulin concentrations than those eating high-carbohydrate foods. Insulin decreases the release of FFA from peripheral adipose stores through its inhibitory effects on the activity of hormone-sensitive lipase. Dogs rely more heavily on FFA for energy generation at all exercise intensities than people do; therefore, the effect of food on resting
insulin levels is a matter of even greater concern for working and sporting dogs. Increased dietary fat (from 25 to 65% of kcal) increases VO2 max and the maximal rate of fat oxidation by 20 to 30% in well-trained dogs. These increases were associated with a 25 to 30% increase in mitochondrial volume, possibly accounting for the increased oxidative capacity. Protein and total caloric intake were identical between groups. Also, event anticipation can suppress insulin concentrations before and during an event activity. The relationship between fat intake and canine endurance is well established. The time to exhaustion for well-conditioned dogs running on a treadmill was directly related to energy density, digestibility and digestible fat intake. Practical applications of this concept are evident in the performance foods currently fed to many successful working and sporting dogs. As the duration of the event performed by a dog increases, so should the dietary fat intake. Dogs can tolerate high levels of dietary fat if fat is gradually (CONTINUED BELOW)

 

(CONTINUED) introduced and an adequate intake of non-fat nutrients is maintained. Steatorrhea and a decrease in food palatability are indicators that the fat content of a food has exceeded a dog’s fat tolerance. Under conditions of extreme training, sled dogs may ingest up to 60% of their energy as fat.During ultra-endurance
events, such as the Iditarod or the Yukon Quest, fat intake may compose 80% of the calories ingested.d This “super fat loading” should be attempted only during the most strenuous periods of such events, when it is difficult or impossible for dogs to ingest as much energy as they are expending. Anemia has been associated with impaired performance in dog teams fed very high-fat foods (i.e., 80% kcal from fat) for prolonged periods (i.e., weeks to months) However, during several long expeditions (including the trans-Antarctica expedition of 1991),Will Steger observed no decrement of performance when dogs were fed food containing 80% fat kcal and 17% protein kcal.e Other factors such as environment, training and dietary intake of non-fat nutrients (e.g., protein) may play a role in the development of anemia. The type of fat used must also be considered in the formulation of foods for working and sporting dogs. Essential fatty acids
should make up at least 2% of the DM of a food. The remainder of the fat may come from any of a number of plant or animal sources. Many greyhound and sled-dog trainers believe that dogs run “hotter” when fed saturated rather than unsaturated fats. No objective evidence supports this theory. However, there is evidence that foods containing high levels of saturated fat (60% of the fatty acids saturated) will reduce olfactory performance in dogs, particularly if they are not physically conditioned. This may be due to effects of dietary fatty acids on brain function. Membrane composition of the central nervous system can be affected by the dietary fat source. Rats fed food high in saturated fat (beef tallow) showed a deficiency of 18:3 fatty acids in the brain vs. rats fed a food with unsaturated fat (corn oil). The fatty acid composition of membrane phospholipids dictates membrane fluidity and permeability. Changes in membrane fluidity can affect the functions of membrane enzymes. Sodium-potassium ATPase is one of several major components of the pathway that mediates molecular events of olfaction. Dietary fat can affect brain synaptic membrane sodium-potassium ATPase activity. In the study above that noted a decrease in
olfaction when 60% of the fatty acids were saturated (37% unsaturated), another group of dogs fed a food with only 24.5% saturated fatty acids (72% unsaturated) maintained olfactory performance over time, even if the dogs were not physically fit. Thus, higher levels of unsaturated fatty acids in a food appear to protect against decline of olfaction over time in untrained dogs. Anecdotal reports support the use of supplemental unsaturated fatty acids (corn oil) to improve olfactory performance.f If corn oil is added to dry commercial foods to increase the fat and/or unsaturated fatty acid content, 1 tablespoon of corn oil for approximately each pound of dry food will increase the overall fat content by about three percentage points. For example, if two tablespoons of corn oil are added to one pound of dry food that contains 20% fat, the resultant mixture of food and corn oil will contain about 26% fat and would have increased levels of unsaturated fatty acids. However, if commercial foods are properly formulated for active dogs, supplementation with fat sources such as corn oil should not be necessary. Alternatively, large intakes of unsaturated fatty acids may increase the risk of oxidative damage to membrane lipids, which can severely damage cell membrane function with potentially disastrous implications for working dogs. Relative to their sedentary colleagues, dogs participating in endurance events are at particular risk for developing oxidative membrane damage because they consume more fat and metabolize more oxygen per unit body weight per day.
Feeding only well-stabilized (preserved) unsaturated fatty acids reduces the risk of oxidative damage to tissues. Increasing intake of vitamins E and C and selenium to bolster cellular antioxidant capacity has also been recommended and is discussed below in the Antioxidants section. Unsaturated fatty acids are an important component in a well-balanced food. As mentioned above, they are largely responsible for membrane fluidity, a property critical to the function of all cell membranes. Unsaturated fatty acids are also required for biosynthesis of many regulatory molecules and maintenance of epidermal integrity. All essential fatty acids are unsaturated. In weighing the biologic significance of unsaturated fatty acids with the possible health risks associated with their fatty acids may be the best solution. For commercial foods, product labels will include ingredient listings in overconsumption, balanced amounts of saturated and unsaturated
descending order of predominance by weight. By reviewing a product’s ingredient list, one can obtain an approximate idea of the levels of saturated and unsaturated fatty acids in the food. If additional unsaturated fat sources are added to a commercial food, adequate vitamin E should be provided. (See Antioxidants discussion, below.) Certain fatty acids are purported to have ergogenic effects. The omega-3 (n-3) family of fatty acids contained in fish oils
has been reported to enhance oxygen uptake.The results reported in this study lacked statistical significance, prompting the need for further investigations.
Medium-chain triglyceride (MCT) supplementation reportedly enhances performance. These intermediate length (eight to 12 carbon) fatty acids do not rely on L-carnitine for transport across the inner mitochondrial membrane. Because they bypass this rate-limiting step in fatty acid oxidation, some investigators
have theorized that increasing the dietary MCT level may increase the maximal rate of fatty acid oxidation. A study of the effects of MCT supplementation failed to demonstrate an increase in oxygen consumption or FFA oxidation in human athletes. Further research is needed to determine the consequences
of MCT supplementation in working dogs. Sprint exercise depends almost entirely on carbohydrate; therefore, the fat requirement for sprinters is not different than that for other dogs.Total fat content should be 8 to 10% of DM or 20 to 24% of kcal. Dietary fat needs for intermediate athletes are directly proportional to the amount of work done. Part-time athletes during off-season should be fed as other dogs. Dietary fat content should be increased as the amount of
work increases: 15 to 30% DM (30 to 55% fat kcal) for moderate amounts of work and 25 to 40% DM (45 to 65% fat kcal) for large amounts of work. Endurance athletes require very high levels of dietary fat to meet their energy needs, in excess of 50% DM and 75% fat kcal. A balance of saturated and unsaturated
fat sources is recommended. Currently, it is recommended that working and sporting dogs not be fed high-fat meals immediately before or during intense
exercise.

Digestible Carbohydrate

Provided sufficient gluconeogenic precursors are available, dogs have no dietary requirement for carbohydrates except during gestation and neonatal development. Dogs are quite capable of maintaining normal blood glucose and tissue glycogen levels when fed carbohydrate-free foods. Compared with people, dogs are less likely to develop ketosis during long periods of exercise or starvation. Despite these facts, dogs have great ability to use carbohydrate.
Canine athletes requiring less than twice maintenance levels of energy may derive a significant portion of their kcal from carbohydrate sources. This is an advantage for high-power athletes, such as racing greyhounds that are highly dependent on anaerobic metabolism. Because carbohydrates contain only
about 3.5 kcal (15 kJ) ME/g, they cannot be used to increase the energy density of a food. This limitation is an important consideration for endurance athletes that have difficulty ingesting a sufficient volume of food to meet caloric requirements. Racing greyhounds are highly dependent on carbohydrate stored in muscles as glycogen because they must mobilize energy quickly to run a race. Studies have shown that greyhounds use significant amounts of glycogen during a race; up to 70% of available glycogen in some muscles for an 800-meter race. Furthermore, evidence suggests that the rate of glycogen use (and, therefore,
energy production) depends on the concentration of glycogen in muscle. It is logical; therefore, to hypothesize that increasing muscle glycogen will enhance
sprint performance. Muscle glycogen content can be increased through a combination of dietary and training protocol changes in some animals (rats, people, horses; these techniques have been used as a means of improving endurance performance The possible benefits of increased muscle glycogen on sprint exercise performance of dogs have not been established. It is also unclear if continuous feeding of high-carbohydrate foods to dogs will increase muscle glycogen. For sled dogs, it may be more advantageous to promote glycogen sparing by feeding a high-fat food than increasing pre-exercise glycogen concentrations via ingestion of a high-carbohydrate food. Studies have demonstrated an increase in the amount of muscle glycogen stored and a greater rate of glycogen use in
sled dogs fed a high-carbohydrate food (65% of kcal). When isocaloric amounts of a high-fat food were fed, glycogen was used at a much slower rate, promoting better endurance at all submaximal exercise intensities. In sled dogs, carbohydrate sparing appears to be a more successful strategy than carbohydrate loading.
Two studies have reported the effect of different fat and carbohydrate levels on race time in greyhounds. Both studies used seven adult racing greyhounds in a crossover design and used race time in a 5/16-mile (502-m) race as the measure of performance. Investigators in the first study used two foods similar in composition except for fat and carbohydrate content. The high-carbohydrate food contained 16% DM fat (34% of kcal) and 52% DM carbohydrate (44% of kcal),
whereas the low-carbohydrate food contained 56% fat (80% of kcal) and 8% carbohydrate (5% of kcal).No significant difference in race times between the two food groups was detected for the first four weekly measurements. At the end of the fifth week, the dogs fed the high-carbohydrate food ran faster
(33.08 ± 0.05 sec) than when they were fed the low-carbohydrate food (33.34 ± 0.05 sec). The results were statistically significant (p <0.05). In this study, dogs performed better when fed a high-carbohydrate/low-fat food than they did when fed a high-fat/low-carbohydrate food. The delay before differences
= 0.2). Neither of these studies evaluated a truly high-carbohydrate level (60 to 70% of dietary kcal) as is now recommended for glycogen loading in people. Furthermore, although the results of these two studies are mixed, physiologic (CONTINUED BELOW).

 

(CONTINUED)principles suggest that carbohydrate supplementation should benefit racing greyhounds. Even endurance athletes may benefit from a low level of dietary carbohydrate. Studies involving sled dogs fed 0 or 17% of their kcal as carbohydrate showed that dogs were more susceptible to developing “stress” diarrhea when fed foods devoid of carbohydrate.There are other advantages associated with feeding carbohydrates to sprint athletes. Because these dogs derive more of their energy for exercise from glucose/glycogen, glycogen depletion may play a role in the onset of fatigue for athletes working at or above their anaerobic threshold Carbohydrate availability to working muscles is a limiting factor for prolonged exercise in people and other species. This finding has led to development of strategies for carbohydrate loading or glycogen super-compensation. The classic method (Åstrand method) uses a combination of exhaustive exercise and low-carbohydrate foods (
high-carbohydrate foods (80 to 90% kcal from carbohydrate) and little activity. This method dramatically increases muscle glycogen in people.An alternative carbohydrate-loading method (Sherman/Costill method) simply requires consumption of 60 to 70% of kcal from carbohydrate consistently over time. In
people, this method produces results similar to those achieved by the classic method. Glycogen loading is probably not as beneficial for canine endurance athletes as continuous feeding of foods with high-fat levels. However, high-power athletes (e.g., racing greyhounds) should benefit from glycogen loading. Because racing greyhounds do not have dramatically increased energy needs and cannot use fatty acids effectively during a race lasting less than 60 seconds, there is no benefit to feeding high levels of fat. Additionally, glycogen stores are rapidly mobilized during racing. In one study, greyhounds running an 800-m race in 48 seconds mobilized 50 to 70% of their glycogen stores in specific running muscles. Studies in people have shown that feeding moderate amounts of carbohydrate (2 g glucose/kg body weight) during a brief postexercise time window permits very rapid rates of glycogen resynthesis. This period begins about 30 minutes postexercise Glucose administered during this window permits up to four times the rate of glycogen resynthesis supported by the same amount of glucose administered after this two-hour window. The form of the glucose (i.e., polymer or simple sugar) does not seem to affect the rate of glycogen repletion. Severely hypertonic solutions should be avoided to prevent excessive osmotic movement of fluid into the gut, which may lead to cramping and GI distress.
This strategy for glycogen repletion is effective in human athletes and dogs. Glucose solutions (from 1.5 to 3 g glucose/kg body weight) given before, during or after exercise have been shown to minimize the exercise-associated decline in blood glucose, promote more rapid repletion of muscle glycogen postexercise and improve thermoregulation. Although only speculation, resultant improvements in exercise performance and thermoregulation might also protect against a reduction in olfactory performance by precluding excessive panting.The carbohydrates used in foods for canine athletes should be highly digestible to limit fecal bulk. Excessive amounts of undigested carbohydrates reaching the colon may increase water loss via the stool, increase colonic gas production and increase overall fecal bulk. These changes in fecal consistency have been proposed to increase an athlete’s risk of developing “stress diarrhea,” further increasing fecal water losses Bulky stools have also been associated with rectal bleeding during exercise-induced colonic evacuation Excessive fecal bulk is also extra weight that
must be carried by the athlete. One study estimated that 150 g of extra stool generated by a racing-sled dog was equal to a 7-kg handicap for a thoroughbred horse. Metabolic power or a high rate of ATP generation is required for sprint performance.Consequently, anaerobic metabolism of glucose and glycogen is the dominant energy generation pathway. High-carbohydrate foods should be fed to maximize muscle glycogen. Dietary carbohydrates should compose 50 to 70%
of total kcal to maximize muscle glycogen levels (based on research done with people).
The dietary carbohydrate recommendation for intermediate athletes is highly variable, depending on the intensity and duration of work. Dogs that perform relatively long bouts of low to moderate intensity work require more dietary energy (higher fat) and relatively low carbohydrate levels (as low as 15% of kcal). Dogs that perform short bursts of higher intensity work should be fed more carbohydrate, up to 50% of kcal. Endurance athletes require very little carbohydrate.
Endurance rations should contain less than 15% of kcal from carbohydrate to achieve the energy density required for the amount of work done by these dogs. Some carbohydrate and/or soluble fiber should be included in the food to avoid loose stools. Technically, the total carbohydrate portion of a food includes
fiber. The digestible (soluble) carbohydrate portion of total carbohydrate consists of starches and sugars, typically referred to simply as “carbohydrate.” The digestible carbohydrate fraction of a food is also called the nitrogen-free extract (NFE). The percent digestible carbohydrate is usually not stated on the
guaranteed analysis listing of a commercial product’s label. Such information should be available from product literature supplied by the manufacturer (e.g., product “keys,” websites, etc.). However, percent digestible carbohydrate can also be estimated from the guaranteed analysis listing by subtracting the
percent crude protein, fat, crude fiber and ash (mineral) from 100. If fiber and ash are not listed, assume 3% fiber and 9% ash in dry foods and 1% fiber and 6% ash in moist (canned) foods. Another, perhaps simpler means of estimating digestible carbohydrate content is to check if the protein and fat recommendations
are close to what is listed on the guaranteed analysis portion of the label of the food in question, if they are, its digestible carbohydrate content should also be close to what is recommended. Soluble fiber and resistant starches may provide some bene-fit to racing dogs, particularly if they are fed raw meat. Rapid
fermentation of oligosaccharides may decrease colonic pH and inhibit clostridial growth. Fructooligosaccharides inhibit cecal colonization by Salmonella
species in chickens and could conceivably do so in dogs.

Protein

Dietary protein is used to fulfill structural, biochemical and, to a lesser extent, energy requirements. Work increases the requirement for protein. The magnitude of this increase and the best strategy for meeting it are subjects of much debate in canine performance nutrition. The work-induced elevation in protein requirement is most pronounced when the intensity and/or duration of exercise performed is rapidly increased above an animal’s present level of
conditioning. These circumstances are encountered at the onset of a training program, when the duration or intensity of training bouts is increased and especially during performances. A common example would be when a bird dog that is also a minimally active pet is hunted the first time during hunting season with little or no exercise training. The increase in protein demand is due to combined increases in the rates of tissue protein synthesis and catabolism.
Several anabolic processes contribute to the exerciseinduced increment in protein requirement. Protein demand is elevated due to an increase in the synthesis of structural and functional proteins. Training induces synthesis of many enzymes and transport proteins in each of the energy-generating pathways. Blood volume also expands during aerobic training. Such expansion necessitates an increase in plasma protein synthesis to maintain oncotic and osmotic balance between plasma and interstitial fluids The increase in hematocrit sometimes observed during endurance conditioning programs may reflect an increase in tissue protein synthesis. Anaerobic training regimens may also induce muscle hypertrophy Amino acids are used in the formation of new muscle tissue and in the repair of damagethat may occur to muscle and connective tissue during intensive conditioning programs. In addition to enhancing the rate of tissue protein synthesis, exercise increases the rate of amino acid catabolism.Amino acids may provide between 5 and 15% of the energy used during exercise, depending on the intensity and duration of the task. Most of this energy comes from the oxidation of branched-chain amino acids. All three amino acids belonging to this group (leucine, isoleucine, valine) are “essential” and thus cannot be synthesized from other amino acids in sufficient quantities to meet requirements. The
branched-chain amino acids lost through exercise must be replaced through dietary intake. The proportion of energy supplied by amino acids may be
even greater in underfed athletes and those participating in ultra-endurance events in which there is a high risk for depletion of endogenous carbohydrate stores. In these instances, gluconeogenesis becomes the major pathway for maintaining blood glucose levels. Because amino acids are the predominant substrate used by the gluconeogenic pathway, their rate of catabolism is increased whenever this pathway is accelerated. This concept raises an important point: it is disadvantageous for an athlete to rely heavily on endogenous sources of protein for energy. There are no known labile stores of protein in the
canine body. All protein sources serve a structural or functional purpose. Interestingly, skeletal muscle is readily mobilized. Overuse of this source would have an obvious negative impact on performance. Because the small pool of circulating amino acids is insufficient to meet the amino acid
requirements of the anabolic and catabolic processes described above, dietary protein intake must supply the deficit if nitrogen balance is to be maintained.
For endurance athletes, there may be some disadvantages inherent to exploiting dietary protein sources for energy. Protein has only about 3.5 kcal (15 kJ) ME/g DM. Thus, increasing the proportion of protein in the formulation cannot increase the energy density of a ration. The energy density of the food is one of the major determinants of endurance capacity when working dogs have difficulty ingesting as many kcal as they expend. Excessive protein intake may predispose an animal to increased amino acid catabolism because dietary amino acids are not stored in labile protein depots, but are deaminated. The resulting ketoacids are either oxidized for energy directly or converted into fatty acids and/or glucose and then stored as adipose tissue or glycogen. The urea produced from amino acid breakdown is excreted from the body in urine. In healthy animals, the amount of water lost increases with increased urea production.
An optimal food for a working or sporting dog should contain enough high-quality protein to meet the dog’s anabolic (CONTINUED BELOW).

 

(CONTINUED) requirements and enough non-protein energy nutrients to meet its energy requirements. Such a food encourages the use of ingested protein in synthetic rather than energy-generating processes. As non-protein caloric intake increases, less dietary protein is used for energy and more is available for use in anabolic processes. Energy requirements should be met by fat and carbohydrate, leaving the majority of amino acids available for synthetic purposes. During long-duration exercise, DER may increase several-fold whereas protein requirement increases only a few percent. To meet the energy needs of hard-working
dogs, either more food must be consumed (increasing both energy and protein intake equally) or a higher energy, lower protein food must be fed (increasing energy intake more than protein intake). Providing sufficient dietary energy by increasing fat content should limit the use of amino acids for energy production. Because the protein requirement is actually a requirement for available amino acids, the digestibility and essential amino acid content of ingested protein will also determine how efficiently amino acids are incorporated into tissue proteins. Research attempts that define the optimal dietary protein intake for working dogs have been inconclusive. Several field studies performed on racing-sled dogs in the 1970s and early 1980s found that well-conditioned dogs fed a high-fat, high protein food maintained higher packed cell volumes and serum albumin concentrations than those fed a relatively high-carbohydrate, low-protein food. The investigators concluded that the high-fat, high-protein food might offer a performance advantage by maintaining better blood volume and oxygen carrying capacity than the other foods tested. These investigators recommended that 30 to 40% of kcal of a performance ration should come from protein. Another study examined the effects of feeding isocaloric foods (4.5 kcal [19 kJ] ME/g) containing 16, 24, 32 or 40% of their energy as protein on performance and biochemical
parameters. During training and racing, dogs fed only 16% of ME as protein suffered significantly more injuries and had a significant decline in VO2 max when compared with age-, gender- and ability-matched sled dogs fed 24, 32 or 40% of ME as protein.Additionally in people, long-duration exercise leading to glycogen depletion increases protein requirement more than weight lifting. There were no noticeable differences in performance between the dogs fed 24, 32 or 40% of ME as protein, although the dogs fed 40% of ME as protein maintained a significantly higher packed cell volume and total plasma volume. This study indicated
that 16% of ME as protein may be insufficient to meet the needs of extremely hard-working dogs and that such animals should ingest a minimum of 24% of their energy requirement as protein. Work in greyhounds shows a different response to food protein levels. When raced for 500 m twice/week, dogs ran 0.3
km/hr faster and their hematocrits were higher when fed a lower protein (63 g/1,000 kcal, 24% ME), higher carbohydrate (106 g/1,000 kcal, 43% ME) food vs. a higher protein (96 g/1,000 kcal, 37% ME), lower carbohydrate (75 g/1,000 kcal, 30% ME) food (Hill et al, 2001a). The fat content of the foods was similar. Thus, for sprint athletes, a lower level of food protein appears desirable. The protein requirement for exercise is only mildly increased (5 to 15%) regardless of exercise type. Protein is used for muscle hypertrophy and muscle maintenance/repair. Furthermore, the branched-chain amino acids can contribute to energy production. Dietary protein should be at least 24% of kcal. Because the energy requirement of some endurance athletes is so high (up to 11 x RER), it may not be feasible to feed even this level of protein and provide adequate kcal. For these dogs, 16% of the ME as protein should be viewed as an absolute minimum.Note that for endurance exercise, energy requirement increases up to 11-fold, whereas protein requirements increase much less (5 to15%). For a given food, as intake increases to meet energy requirements, protein intake increases proportionally. Because of the disparity between the increase in need for energy and protein for exercise, as total dietary energy requirement increases, the percent of the ME as protein of the food can decrease.

Digestibility

DM digestibility of food is important to canine athletes for two reasons. First, exercise may be limited by a dog’s ability to obtain sufficient amounts of nutrients (usually energy). Enhanced digestibility increases the maximum possible delivery of nutrients to tissues. Second, lower digestibility means
greater fecal bulk, and therefore a greater handicap. Although increased animal size results in greater running efficiency, increased fecal weight creates a greater energetic cost of running with no benefit. Total DM digestibility of any food for canine athletes should exceed 80%. Foods having a higher energy density are likely to have increased DM digestibility.

Antioxidants

There are at least two questions to consider when discussing antioxidants for working and sporting dogs: 1) do supplemental antioxidants provide a health benefit and 2) do they influence performance. Exercise is associated with an increase in the rate of oxygen consumption. The extent of the increase depends on the intensity of the exercise. Even normal oxidative metabolism results in the production of highly reactive free radical molecules. Proportionate increases in free radical production appear to accompany exercise-associated increases in oxygen consumption. Aerobic, anaerobic and mixed exercise cause varying degrees of free radical production. Besides mitochondrial production of free radicals, such as with endurance exercise, anaerobic and mixed exercise result in ischemia reperfusion, acidosis and catecholamine oxidation that further contribute to oxidative stress. The body’s typical adaptive response is increased mobilization of a variety of enzymatic and non-enzymatic antioxidant systems. However, with exercise these innate antioxidant capabilities are oftentimes overwhelmed, which leads to oxidative stress. The consequences of prolonged oxidative stress may contribute to and/or exacerbate a wide variety of degenerative diseases. In human athletes, unchecked oxidative stress seems to be involved in chronic muscular fatigue and may lead to a condition called “overtraining”. It is possible that canine athletes experience a similar phenomenon. Considerable research into the use of supplemental antioxidants
to augment the body’s antioxidant capacity during exercise has been done in a variety of species. However, because of the complexity of the associated variables, many of the research results are equivocal making it challenging to apply the knowledge to practice. These complexities include degree of training,
positive effects of free radicals, doses of antioxidant supplements and the number of different antioxidant supplements used. Oxidative stress can be mitigated to a degree through training. In marathon runners, free radicals generated during exercise up-regulated the expression of antioxidant enzyme systems Also, in other studies, endurance, anaerobic and mixed exercise training programs reduced postexercise oxidative stress. he positive effects of training are seen in antioxidant enzyme systems in muscle, fat, plasma, liver and heart. In one study in minimally trained dogs, the antioxidant mechanisms were insufficient to meet the antioxidant needs associated with repetitive endurance exercise. Not surprisingly, training matters. Many hunting dogs have a leisurely lifestyle for most of the year, associated with being the family pet. However, on the opening day of hunting season, they are expected to function at peak athletic performance. Such dogs should have adequate levels of antioxidants in their food. Better yet, combine that recommendation with a preseason exercise-training program. It should be noted that free radicals appear to also have a physiologic function and total mitigation of reactive oxygen molecules can negatively affect certain types of exercise performance. In human subjects, free radicals have been shown to have a regulatory function at the vascular level, causing vasodilatation. Excessive doses of antioxidants have been shown to impair muscle force production.When racing greyhounds were supplemented
with high doses (1 g/day) of vitamin C, they ran slower. Racing greyhounds also ran slower when supplemented with high doses of vitamin E (1,000 IU/day) but not lower doses (100 IU/day) Besides interfering with normal redox signaling, high doses of antioxidants, particularly of individual antioxidant supplements,
-tocopherol radical can exhibit pro-oxidant activity. Antioxidant balance is important because supplementation with large amounts of a single antioxidant may change the balance to one of a pro-oxidative state. High doses of vitamin C and selenium may act as pro-oxidants. Multi-nutrient antioxidant supplementation using lower doses is a better approach. Commonly supplemente-tocopherol. If co-antioxidants are absent or decreased, the -tocopherol radical back to -tocopherol radical. Normally, co-antioxidants, such as vitamin C, reduce the can be counterproductive in a different way. Single antioxidant supplementation can have a pro-oxidant effect. For example, as part of its antioxidant function, vitamin E temporarily becomes a radical species known as the -carotene and other carotenoids, selenium and thiols. Fruits and vegetables are good sources of flavonoids,d food-source antioxidants include vitamins E and C,
polyphenols and anthocyanidins. The following recommendations, however, will focus on vitamins E and C and selenium as antioxidant key nutritional factors because: 1) they are biologically important, 2) they act synergistically and 3) there is pub published information regarding safety and inclusion levels.

VITAMIN E

Vitamin E is the primary lipid-soluble antioxidant in plasma, erythrocytes and tissues. It is transported in plasma proteins and partitions into membranes and fat storage sites where it is one of the most effective antioxidants for protecting polyunsaturated fatty acids from oxidation.The minimum DM requirement for vitamin E for foods for adult dogs is 30 mg/kg Research indicates that a higher level of vitamin E confers specific biologic benefits. In minimally trained sled
-carotene and lutein resulted in increased plasma concentrations of antioxidantsand decreased DNA and lipoprotein oxidation. In a study that measured plasma vitamin E concentrations in racing-sled dogs during the 1998 Iditarod Race, dogs that had high pre-race vitamin E concentrations were almost twice as likely to finish the race. These results could reflect a higher vitamin E intake and/or better fitness and a resultant higher anaerobic threshold. As noted above, unchecked oxidative stress can result in muscle fatigue. Endurance exercise in sled dogs results in considerable oxidative stress. Trained subjects present a higher vitamin E status whereas overreaching seems to decrease it. (CONTINUED BELOW)

 

(CONTINUED) Based on antioxidant biomarker studies in non-exercising dogs, for improved antioxidant performance, dog foods should contain at least 500 IU/kg of DM vitamin E. For a 25-kg dog engaged in moderate exercise for several hours/day, this would amount to approximately 250 IU/day. Compared to the amounts in the studies mentioned above, this is not an excessive amount.

VITAMIN C

Vitamin C is the most powerful reducing agent available to cells. As mentioned above, it is an important co-antioxidant because it regenerates oxidized vitamin E. Besides regenerating vitamin E, vitamin C also: 1) regenerates glutathione and flavonoids, 2) quenches free radicals both intra- and extracellularly,
3) protects against free radical-mediated protein inactivation associated with oxidative bursts of neutrophils, 4) maintains transition metals in reduced form and 5) may quench free radical intermediates of carcinogen metabolism. Dogs can synthesize amounts of vitamin C required for maintenance and they can rapidly absorb supplemental vitamin C. However, in-vitro studies indicated that dogs have from one-quarter to one-tenth the ability to synthesize vitamin C as other mammals. Whether or not this translates to a reduced ability in vivo is unknown. Studies in exercising people and horses have shown improvements
in indicators of oxidative stress associated with exercise as a result of vitamin C supplementation. However, as mentioned above, a study in greyhounds that were supplemented with high doses of vitamin C resulted in slower racing times. As mentioned previously, multi-nutrient antioxidant supplementation using lower doses is a better approach than using high doses of a single antioxidant supplement. To augment antioxidant protection, in conjunction with recommended levels of vitamin E above, improved antioxidant performance foods for working and sporting dogs should contain between 150 to 250 mg of vitavitamin C/kg (DM). The upper end of this range would be about 70 to 100 mg/day for a 30-kg dog. This is about 7 to 10% of the amount (1 g/day) that slowed race times in the greyhound study described above.

SELENIUM

Glutathione-peroxidase is a selenium-containing antioxidant enzyme that defends tissues against oxidative stress by catalyzing the reduction of H2O2 and organic hydroperoxides and by sparing vitamin E. In people, following eccentric exercise- induced muscle injury, suboptimal selenium status worsens muscle functional decrements. The minimum requirement for selenium in foods for dogs is 0.10 mg/kg (DM). Animal studies and clinical intervention trials in people
have shown selenium to be anticarcinogenic at much higher levels (five to 10 times) than the human recommended allowance or minimal requirement.
Several mechanisms have been proposed for this effect, including enhanced antioxidant activity via glutathione peroxidase.Therefore, for increased antioxidant benefits, the recommended range of selenium for dog foods is 0.5 to 1.3 mg/kg (DM). There are no data to base a safe upper limit of selenium for dogs, but for regulatory purposes, a maximum standard of 2.0 mg/kg (DM) has been set for dog foods in the United States

Other Nutritional Factors

Vitamins, minerals and electrolytes play important roles in maintaining homeostasis and chemical reactions during exercise However, they are of secondary concern when feeding canine athletes and are found in adequate amounts in most commercial foods. Likewise, the acidbase composition of the food and base loading may also affect performance; however, these effects are poorly understood in canine athletes. Deficiencies of vitamin A, iodine and zinc have been associated with disturbances of smell in people but are not of practical concern in dogs being fed commercial foods.

FEEDING PLAN

The feeding plan should be formulated based on realistic and quantifiable nutritional objectives after the patient, food and feeding method have been assessed. The feeding plan guides the selection of foods and feeding methods.

Assess and Select the Food

Although the working or sporting dog’s nutritional needs could conceivably be met by many different dietary approaches, all foods for canine athletes (performance foods) should share a few important characteristics. First, the food should be calori-cally dense so that canine athletes can consume enough food to meet their energy requirements. Second, the food must be acceptable and highly digestible. DM digestibility should exceed 80%. High digestibility reduces fecal bulk and fecal water loss and may decrease the risk of developing stress diarrhea. Finally, the food should be practical. Factors such as the cost of the food, the form of the food, the environment in which the food is stored and fed and the number of dogs being fed are all important considerations.What is
practical for a single hunting dog at home may not be practicalfor a team of sled dogs hundreds of miles from civilization, fighting dogs at an out-of-town competition or racing greyhounds at a track. Because the greatest nutritional demand of exercise is for energy, foods for canine athletes must provide sufficient kcal from the right sources. Increasing the fat content of the food usually enhances energy density. The appropriate fat content is dictated by energy need and exercise intensity. Dogs participating in short-duration, maximal exercise may benefit from lower fat, higher carbohydrate foods. Assessment of the food includes: 1) physical evaluation of the food, 2) evaluation of the product label for commercial foods and 3) evaluation of the food’s nutritional content relative to the animal’s needs (key nutritional factors). Working and sporting dogs are fed a wide variety of foods and supplements. When assessing the overall ration, it is important to assess all foods and supplements fed. The nutrient profile of the total daily ration should be evaluated for the key nutritional factors based
on the type and amount of exercise performed by each dog. Most intermediate athletes are fed commercial foods, whereas many elite sprint and endurance athletes (racing dogs) are fed homemade foods or more commonly a mixture of commercial food and other ingredients. The use of supplements is prevalent with working and sporting dogs of all types. Comparing the nutritional content of the current food to the key nutritional factors allows decisions to be made about the adequacy of the food for individual dogs. If the current food is appropriate (key nutritional factors in balance with the dog’s needs) then that food can continue to be fed. If discrepancies exist between the key nutritional factors for the dog and the content of the food, the food should be changed or “balanced”
to meet the dog’s needs.

Commercial Foods

Lists the key nutritional factors for working and sporting dogs and compares them to the key nutritional factor content of selected commercial foods formulated for these dogs. Minimum fat and protein levels are listed in the guaranteed or typical analysis on the pet food label.The carbohydrate portion of a food
can also be estimated as described above under “Carbohydrates” in the “Key Nutritional Factors”. Digestibility information is usually only available from the
manufacturer. The energy density of most commercial foods is not high enough for dogs engaged in true endurance activity. Comercial food must provide energy density information for commercial foods supplemented with vegetable oil in order to meet the energy density needs for endurance athletes.
.
Homemade Foods

Homemade foods can be very complicated mixtures of many ingredients. Fortunately, most recipes for homemade foods for working and sporting dogs use a commercial dry dog food as a base. Many racing greyhound food regimens contain dry dog food mixed with either raw or cooked meat, water, vitamin
mineral supplements and a variety of other ingredients. Likewise, many sled-dog mushers mix animal fat or both meat and fat with dry dog food and other ingredients. If the commercial dry food constitutes 50 to 75% of the mixture on a weight basis and most of the added ingredients are wet ingredients
or fat, it is unlikely that vitamin and mineral deficiencies will occur. Because many elite canine athletes (racing greyhounds and sled dogs) are fed homemade foods containing meat and animal by-products of variable quality, the safety of these foods should always be evaluated. Some raw meat sources contain
abundant bacteria and bacterial toxins. Raw foods may pose a health hazard for people who care for these dogs and for the dogs themselves.

Supplements

Feeding glucose solutions minimizes the exercise-associated decline in blood glucose, promotes more rapid repletion of muscle glycogen post exercise and improves thermoregulation. However, when such solutions are fed is important. Glucose solutions (from 1.5- to as much as 5-g glucose/kg body weight)
have been used. As an option to a glucose solution, an anecdotal report recommends using up to one 8- oz. measuring cup of sucrose per quart of water (~240 g/l).fTo receive an amount of sucrose equal to the upper end of the previously recommended range for glucose (5 g/kg body weight), a 35-kg dog would have to ingest approximately three-fourths of a quart of the sucrose-water solution. Several commercial products are available to support energy levels during exercise. These products are available as powders to be added to drinking water (so called “canine sports drinks”) or dry snacks. They can be found online or at pet or sporting goods stores. Small amounts of a high-carbohydrate low-fat commercial dog food could also be used for this purpose. Vegetable oils (plant-source edible oils, e.g., corn oil and soybean oil) can be used to increase the unsaturated fatty acid content
of a commercial food for improving olfaction (see “Fat” under Key Nutritional Factors discussion) and for increasing the energy density of a commercial food. If corn oil is added to dry commercial foods to increase the fat and/or unsaturated fatty acid content, 1 tablespoon of corn oil for approximately each pound of dry food will increase the overall fat content by about three to four percentage points. For example, if two tablespoons of corn oil are added to one pound of dry food that contains 20% fat, the resultant mixture of food and corn oil will contain about 27% fat and would have increased levels of unsaturated fatty acids. Corn and vegetable oils provide about 125 kcal ME/tablespoon (14 g). Comercial foods would need to be supplemented with vegetable oil to increase energy density to a level to support needs for dogs engaged in endurance activity. Dogs can tolerate high levels of dietary fat if the fat is gradually introduced and an adequate intake of nonfat nutrients is maintained. Steatorrhea and a decrease in food palatability are indicators that the fat intake of a food has exceeded an individual dog’s fat tolerance.

Assess and Determine the Feeding Method

Performance can be influenced by the composition of the food and how it is fed. It is possible to feed the right food in the wrong way and vice versa. Items to be assessed should include amount fed, frequency of feeding and timing of meals in relation to exercise, food adaptation, access to water and the use of
supplements. All of these factors should be matched to the individual athlete and the type of exercise performed (intensity, duration, frequency and season). If the current feeding method matches the individual’s needs based on the assessment, no changes are necessary.Changes should be made if the assessment
reveals discrepancies in the feeding method. If the animal is in appropriate body condition and hydration status, it is likely that the amount of food and water consumed is appropriate. The amount of a new food to feed can be estimated several ways. Feeding guidelines from the manufacturer and those on pet food labels are seldom correct for active working and sporting dogs. Energy needs and food doses usually must be calculated. If the amount of the previous food was correct (i.e., appropriate body condition was maintained) and the energy density of the food is known, simply feed the same amount of the new food to supply the same energy intake. If this method isn’t feasible, the food dose should be calculated based on the dog’s needs as shown above. In all cases, the dog should be assessed frequently and adjustments should be made to maintain correct body condition. Timing of feeding and timing of food changes are important
for working and sporting dogs.Timing of feeding in relation to exercise influences hormonal status, substrate availability and performance. When changing foods, adequate time must be allowed for the dog to adapt to the new food type to take full advantage of its nutrient profile. (CONTINUED BELOW)

 

(CONTINUED) Amount to Feed

An increase in energy requirement is the hallmark of exercise. The wide variation in the intensity and duration of exercise and therefore energy requirement of different types of working and sporting dogs emphasizes the need for food dose calculations. The dog’s DER is the product of its RER and a factor that
accounts for activity. For the average, minimally active adult dog, DER is 1.2 to 1.4 RER. DER for exercising dogs has a wide range of values from 1.6 x RER
to 11 x RER, depending on the intensity and duration of exercise. The DER range for sprint dogs is 1.6 to 2 x RER, for intermediate (mixed) type activity the DER range is 2 to 5 x RER, for endurance-type activity the DER is more than 5 x RER. As discussed earlier, the caloric cost of running is determined by the size of the animal (body weight), weight carried or pulled and distance traveled. Energy is also used to maintain body temperature. Extreme arctic and tropical temperatures increase a dog’s RER. Dogs working in cold climates may require less energy than the sum of those determined for work and thermoregulation because exercise generates significant quantities of heat. RER for nonworking dogs in hot environments increases only marginally as a result of increased work of the respiratory muscles (panting)Working dogs already have increased respiratory rates, thus, additional energy for thermoregulation during exercise in hot climates should be negligible. Total DER is the sum of the needs for rest (RER), exercise (EER) and thermoregulation (ET) (i.e., DER for canine athletes = RER + EER + ET). Most working dogs expending fewer kcal than 3 x RER can adequately fulfill their energy needs by eating a commercial food formulated for performance. These foods are palatable, complete/balanced and convenient in most situations. Working and sporting dogs exercising in extremely warm
or extremely cold environments or those working for several hours a day for several consecutive days may expend more calories than 3 x RER. DM intake is limited to about 3.5% of body weight under most physiologic conditions.c A performance food containing these amounts (30% DM protein, 20% DM fat, 40% DM carbohydrate and >80% DM digestibility) provides a maximum of 5 x RER for a 25-kg dog. Because true endurance athletes have a DER greater than 5
x RER, providing sufficient dietary energy becomes the focus of feeding these athletes. Long-distance sled-dog drivers frequently encounter situations in which their 25- to 30-kg dogs require 6,000 to 10,000 kcal/day (25 to 42 MJ/day) (7 to 11 x RER). Under these extreme circumstances, dogs are fed 1,500 to 2,500 kcal (6 to 11 MJ) of a dry commercial food in an attempt to fulfill protein, carbohydrate, vitamin and mineral requirements.Fulfilling the rest of the dog’s DM intake with fat or fatty meat then maximizes energy intake. Strategies that maximize fat intake have been successfully used in virtually all of the recent Iditarod,Quest and Alpirod victories and in sleddog expeditions to both poles.d,e,g,h These extremely high-fat foods, which derive up to 80% of their kcal from lipid sources, should be fed only to dogs previously acclimated to high-fat intake (i.e., 30 to 60% fat kcal), through feeding and training. Also, there may be a limited amount of time that dogs can be maintained on such a food or at such a level of stress. Another strategy used by sled-dog mushers is to feed their
dogs so they begin a long-distance race with 1.36 to 2.3 kg of extra adipose tissue. This gives the dogs a reserve to draw upon when caloric intake cannot meet energy expenditure. The additional insulation may also help dogs reduce heat loss during rest periods. Feeding to Maintain Proper Body Condition Food-dose calculations are based on average energy needs for a population of dogs and therefore will not be accurate for all dogs in various circumstances. Variation in individual metabolic rate, environmental temperature and exercise affect energy requirement and food dose. Repeated or continual body condition
assessment is clearly the best clinical measure of energy balance. Body condition scoring is primarily a measure of body fat. Increasing body fat indicates positive energy balance; therefore, food dosage should be decreased. If body fat falls below optimal, energy balance is negative and food dosage should be
increased to ensure adequate energy for maximal performance. BCS of 2/5 to 3/5 is normal for most working and sporting dogs, with a bias towards the lean side of this range. Hunting dogs’ BCS should be in the range of 2.5/5 to 3.5/5. Unfortunately, some of these dogs will have BCS greater than 3.5/5 because they are pet dogs and thus are more prone to being overweight. Because fat in excess of what is needed for energy reserves during racing adds weight and may affect performance, many sight hounds are kept very lean (BCS 1/5 to 2/5). Most racing greyhounds normally have a BCS of 1/5. Being very lean may
be an important physical characteristic for maximal sprint performance plus the fact that greyhounds have a very limited ability to use fat as an energy source for sprinting. Racing sled dogs should have a BCS of 2.5/5.

When to Feed

To gain maximum benefit from a specific food, meals must be fed at the right time in relation to exercise and ample time must be allowed for metabolism to adapt to a new food type when changing foods. After the amount to feed has been determined, an appropriate feeding schedule should be used. The temporal relationship between food intake and exercise greatly affects nutrient use. In one study, dogs fed within six hours of exercise developed a higher working body temperature than those fed 17 hours before exercise. The elevated body temperatures in dogs fed closer to the onset of exercise may have been caused by heat released by the digestive process (specific dynamic action of food), and by vasodilatation of the splanchnic vessels. Such shunting may decrease cutaneous circulation and thus diminish heat dissipation. In performing the same task, dogs fed within six hours of exercise used more glucose and less fat than post absorptive dogs. Higher circulating insulin levels in the more recently fed dogs may cause this alteration in substrate use. Because insulin tends to decrease free fatty acid mobilization from peripheral adipose depots, feeding too close to exercise may impair endurance by encouraging use and thus depletion of limited carbohydrate (glycogen) stores. The importance of the temporal relationship between feeding and exercise is seen in the poorly documented syndrome known as hunting dog hypoglycemia. The exact etiology of this syndrome is unknown. It is often associated with hyperactive, under-conditioned hunting dogs. Elevated ambient temperature has also been implicated as a risk factor. Dogs experiencing this syndrome begin working normally and then develop signs of weakness and tremors that may progress to seizures and even death. Their purported inability to maintain normoglycemia has been attributed to inadequate glycogen
4) before the onset of exercise may help decrease insulin levels at the onset of exercise. Exercise also dampens the insulin response to ingested carbohydrate. Providing exogenous carbohydrate via small amounts of food offered at the onset of, and periodically during, exercise may aid blood glucose homeostasis in these dogs . It is best if this food is not high in fat.As mentioned above (Supplements), glucose or sucrose solutions can also be used. Such solutions can be given immediately before, during or after exercise and have been shown to minimize the exercise-associated decline in blood glucose, promotemobilization (due to a lack of a glycogen debranching enzyme), excessive rates of glycogen mobilization or a combination of the two. Feeding these dogs several hours (
more rapid repletion of muscle glycogen postexercise and improve thermoregulation. The same timing of feeding is recommended for the several commercial products that are marketed to support energy levels during exercise (specific-purpose hydratable powders and dry snacks). blood glucose results from a study that examined the effect of feeding time on blood glucose concentration during exercise in people riding a stationary bicycle. One group was given a drink containing glucose 45 minutes before the onset of exercise, whereas the other group received a placebo drink. Blood glucose levels remained constant in the non-fed group, whereas people ingesting the glucose drink had a normal postprandial increase in blood glucose followed by a severe drop at the onset of exercise. Feeding long before exercise (more than four hours) may also aid endurance by allowing the dog to evacuate its bowels before it begins work. This decreases the weight carried by the dog and may decrease its risk of developing stress diarrhea. Although the cause of loose stools postexercise has not been determined, some researchers have attributed it to the presence of stool in the colon at the onset of exercise.h As with pre-exercise feedings, the timing of postexercise meals also influences nutrient use. Glycogen synthesis postexercise occurs much more rapidly in human athletes given exogenous substrates within 30 minutes to two hours postexercise. Feeding within this time frame may aid repletion of glycogen stores in athletes who must perform strenuous exercise on several consecutive days. The practical application of the above information is feed: 1) more than four hours before exercise, 2) within two hours after
exercise and 3) small amounts of food during exercise. Feeding must be done during exercise or during short breaks. Feeding a hunting dog that has Hypoglycemic tendencies at the beginning of a 45-minute lunch break may contribute to exercise-induced hypoglycemia . Because large volumes of urine represent additional weight and a possible time handicap for racing dogs, many handlers will not water an animal closer than two hours before a competition.
The dog is then confined for one and one-half to two hours after drinking and will usually empty its bladder upon being released from the cage.Water should be offered as soon as is practicably possible after exercise. Cooler fluids seem to be absorbed most rapidly. Canine athletes may become significantly dehydrated after prolonged exercise and under relatively warm or humid conditions. Attempts should not be made to replace the entire fluid deficit orally or at once. Gradual oral replacement can be supplemented with subcutaneous (or in severe cases intravenous) isotonic solutions. Body temperature should be
monitored because dehydrated animals are less capable of regulating this parameter.

Food Adaptation

Dogs require some time to adapt to a new food whenever a dietary change is made.When dramatic changes in proportion of fat and carbohydrate are made, GI and metabolic adapta-tions occur. The GI adjustments usually happen in a few days provided the transition to the new food is gradual. The metabolic changes generally take more time. Muscle glycogen responds to feeding a high-carbohydrate food in a few days to a few weeks (Reynolds et al, 1995). Changes in muscle enzymes and oxidative capacity occur in response to high-fat rations in six to eight weeks. Allowing appropriate time for these adaptations to occur is especially important for seasonal athletes that may be fed a high-fat performance food only part of the year and a maintenance food the remainder of the year.
Both training and dietary change should occur six weeks before exercise season (e.g., hunting season).

After the feeding plan has been implemented, the dog should be monitored to evaluate the appropriateness of the feeding plan. This process is identical to the original assessment of the dog. Frequent physical examinations are important for early detection of injuries or illnesses. Daily monitoring of food consumption
is an early indicator of problems. Frequent evaluation of stool quality may indicate how well the dog is tolerating the food. Weekly measurements of body condition and weight allow assessment of energy balance (i.e., whether food intake matches energy expenditure). Appropriate body condition is also important for optimal performance. Excess fat represents an unneeded handicap, whereas excessively lean dogs may not have sufficient energy stores. Hydration status should be monitored frequently. Water plays a vital role in supporting cardiovascular function, transport of metabolic substrates and wastes and ermoregulation.
Respiratory water losses can be large, particularly during lengthy exercise or under hot or cold environmental conditions. Ultimately, assessing both exercise and olfactory performance is the best means of monitoring the feeding plan for working and sporting dogs. (THE END)

 

nice read celtic i never thought there was so much to know about muscle design and nourishment. thanks

 

I liked the article because it generalizes between sprint dogs, intermediate dogs and endurance dogs but you're right you'd have to adapt it a bit to suit the Bulldogs but the basis for it is there in the article.

 

The Bulldogs would be closer to the endurance dog requirements.

 

very nice post and paying attention to what slim says too

thanks for sharing

 

Sorry just need to bump this one up to the top again for a short while because its related to another discussion we are having.

 

slim12, i agree, but 2 of the 3 require higher carbs for best development,while the 3rd requires lower carbs and higher fat. So the blending of what, when, how, and why, relating to training feeding and recovery for peak performance, are dependant on the use of the scientific method and total time available to a keep.
If total time was only limited to the scientific method,would it be more beneficial to use a longer keep with a shorter pre keep,or a shorter keep with a longer pre keep in relation to utilizing the sciences of all 3?

 

Ozzie stevens was very knowledgeable aobut conditiooning the gamedog, and he read a lot about different types of supplements and phisiology , and he would work his dogs to be able to work flat out ,and he very rarely lost i think he won 98 % of his 132 matches into the best in his time, so he knew a thing about conditioning and im only sorry i never got him on tape to remember everything he told me but unfortunatley he died unexpectedly in a car crash eventhough he was 83 he was as live as can be and would have been around foryears to come , but at least i got a year of talking to him before he died ,, its a shame he never put out his full keep i think it would have turned a fe2w heads but he was the best ever and hes porbably up in heaven talking dogs with tudor mayfield and the other greats.