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onderstaand las ik op een ander forum, dit was een reactie van een Canadese vriendin na aanleiding van een vraag over het trainen met de honden en de hoge temperaturen van het moment.

ivm de lengte van de tekst heb ik het in meerdere stukken verdeeld

First just wanted to say thanks for the chat tonight. I know we spoke about the heat w/respect to dogs working and I did find some of the sites which I remembered researching a while ago on heat and how nutrition also plays a BIG role in regulating it:

It's an article which explains and supports the role of nutrition in heat regulation and in prevention of hyperthermia. It's an excellent article for all; but even more specific to working dogs...

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I've put in bold the areas I thought to be most important  

"By Hilary Watson

A high-fat diet contributes to increased stamina and protects against heat stress.
Summer will soon be here, and with it, the start of another demanding outdoor canine sport season. While hot weather tends to lower the activity level and hence, the nutrient requirements of most dogs, competitive or working dogs often have increased needs as a result of having to perform in hot, humid conditions. Nutritional strategies that enhance stamina and provide protection from heat stress may be beneficial for these dogs.

Human athletes often follow a feeding strategy called "carbohydrate loading." This approach was first described in 1967 by Bergstrom, who demonstrated that a high-carbohydrate diet in conjunction with athletic training resulted in improved endurance in competing athletes. During exercise, muscle glycogen and blood glucose are the principal fuels for muscle contraction. Depletion of muscle glycogen is associated with muscle fatigue. Bergstrom showed that high-carbohydrate diets slowed muscle-glycogen depletion, thereby improving endurance in human athletes.

Studies in dogs and horses using the same strategy have been disappointing. Carbohydrate loading in sled dogs resulted in exertional rhabdomyolysis, or "tying up" (an excess accumulation of lactic acid in the muscles), and in horses it often caused founder (inflammation of the hooves) and colic. An alternative strategy involving increased levels of dietary fat is preferred for these animals.

High fat intake, in conjunction with endurance training, causes cardiovascular, pulmonary and enzymatic changes that enhance the storage of fat in muscle and increase an animal's ability to use fatty acids as fuel for muscle activity. This process is known as "fat adaptation".

Stamina testing in rats shows improved endurance, better oxygen utilization and reduced depletion of muscle glycogen when high-fat diets are fed, as compared to high-carbohydrate diets. Racing sled dogs have been shown to perform better on high-fat diets, and treadmill studies with beagles have shown that feeding high-fat diets results in a longer period before a state of exhaustion is reached, while a high-carbohydrate intake is associated with a more rapid onset of fatigue.

Fat adaptation is believed to improve efficiency of energy utilization in performance animals. One study showed that in fat- adapted race horses, 77 percent of ingested metabolizable energy was available for athletic activity while the remaining 23 percent was expended to maintain normal metabolic functions. In nonfat-adapted horses, 34 percent of metabolizable energy was required for metabolic functions, leaving only 66 percent for athletic activity. This study proposed that fat adaptation increased the efficiency of energy utilization in the performance animal.

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Fat adaptation may also reduce breathing effort during exercise. During aerobic activity, muscles use oxygen to burn fuels, and carbon dioxide is produced as a by-product. Increased heart and respiration rates during exercise facilitate an increased uptake of oxygen and release of carbon dioxide by the lungs. Less carbon dioxide is produced per unit of oxygen when fatty acids are burned as fuels, as compared to carbohydrates. Fat-adapted horses have lower levels of carbon dioxide in their blood during exercise, and this may reduce the breathing effort required.


Getting Water From Fat

Dehydration is a major concern for all animals competing in hot weather. Dogs lose excess body heat by panting and sweating, so a dog's requirement for water increases with increasing temperature and activity. In most cases, providing an adequate supply of fresh water will prevent dehydration, but in times of prolonged exertion, dietary factors may also help. High levels of dietary fiber, for example, should be avoided, since fiber can increase water loss in the feces.

Fat adaptation has been shown to help maintain hydration in endurance horses during strenuous exercise. This is believed to be due to an increase in the production of "metabolic water" in animals fed high-fat diets. Metabolic water is defined as water produced from the metabolism of nutrients in the body. When 100 grams of fat, protein and carbohydrate are metabolized, approximately 107 grams, 40 grams and 55 grams of metabolic water are produced, respectively. Depletion of water is a major cause of fatigue in performance horses, and higher metabolic-water production may provide a significant advantage in maintaining hydration during prolonged exercise.

Hot weather results in increased stress for the active dog. It is also associated with reduced food intake, which can contribute to loss of condition. Pre-season "training" can enhance a dog's abilities to withstand the rigors of the summer sport season. And increasing the level of dietary fat may benefit performance dogs by providing a more concentrated energy source and promoting adaptive responses that enhance stamina and provide protection against heat stress."
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Another article:

"Do they require higher levels of fat than they have been getting from most commercial foods?

A resounding YES!

We now know that a high-fat diet is of dramatic benefit to a cancer patient. The same is true with a healthy dog or cat, whether he is active or inactive, young or old.

In humans, eating the bulk of your caloric intake with carbohydrates (carb loading) has proven to increase muscle-glycogen; therefore, increasing stamina. The same carb loading tested on sled dogs showed an excess accumulation of lactic acid in the muscles. In horses, it caused founder and colic; therefore, establishing that canines and horses do not metabolize carbohydrates the same way as humans. Cats and dogs metabolize fat the way humans metabolize carbohydrates. It is fuel that gives them the ability to function at their greatest peak of health.

Fat adaptation has shown to reduce the effort of breathing through lowering the levels of carbon dioxide in the blood. Even sedentary pets benefit form the high-fat diet, giving their body what has long been required and allowing it to easily digest.

Dogs and cats maintain better body heat in cold temperatures, and in warmer temperatures, a high-fat diet guards against heat exhaustion and dehydration through fat adaptation. Dogs who are competing in field trials, lure coursing, agility, or any sport requiring excessive effort and using a high-fat diet consume less water than their competitors, giving them the competitive edge. It is believed that, this is through an increase in production of "metabolic water" in animals fed a higher-fat diet.

Metabolic water is water produced from the metabolism of nutrients in the body. Depletion of water is a major cause of fatigue, heat stroke, and in cases that are more serious, heart attack and death.

Hot or cold weather results in increased stress to any animal. When that animal is not getting a quality diet with the proper amount of fat, it takes a toll on their body, reducing their optimum state of health.

An excerpt taken form "Dogs In Canada" The Most Essential Nutrient, June 1998, Hilary Watson states: "Diets moderate in protein but high in fat, tend to help conserve body fluids in three ways".

(1) They minimize urine output by reducing the amount of nitrogen that must be eliminated form the body.
(2) They provide a more concentrated source of nutrients, thereby minimizing stool volume and fecal water losses.
(3) Dietary fat contributes metabolic water defined as water produce form the metabolism of nutrients".

Borrowed from:

http://www.beowulfs.com/magazine/nutrition.htm
http://www.k9power.com/fat'swhere.htm

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As far as helping the dog externally deal with the heat; I would suggest hosing them down or having them stand submerged to belly if possible in water...Paying extra attention to the groin/abdominal area of the dog. Keep them in the shade and in a very well ventilated area and pacing out their exercises. I also had a couple fans in the back of my truck which were attached to their 'crates' when the vehicle was parked. It's extremely important that there is air flow in the vehicle as moisture cannot evaporate in order to cool the dog if the dog is confined in a crate in a vehicle without abundant air flow.
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Preventing Heat Stroke in your Canine Athlete
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Crosspost from Bandog Banter

I've already seen many posts this year on the AB boards over the last few weeks about dogs that have died due to the summer heat. I also encounter it often on the job working as a Animal Warden. I wanted to take the time to post some guide lines for preventing heat stroke in your canine athletes this warm July holiday weekend. Follow these guidelines below for a cooler dog!

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Prevention

1. Make sure your canine athlete is well hydrated before, during and after a physical work out! Use only containers that are originally made to carry water to prevent accidental transfer of dangerous chemicals into their drinking water.

2. If possible, always bring water from your home for your dog to drink at practice and competition.
Do not force or allow your dog to drink too much water at any one time.

3. If you wet your dog down with water to help them cool, soak them to the skin from just behind the ears all of the way down to the tip of the tail. Wetting the abdomen and chest thoroughly is the best water-cooling area as it has the least fur. Wetting just the top of the fur can create a very dangerous problem (thermal barrier created by the wet fur).

4. Never use ice directly on the skin, cool packs are more effective than ice packs. Place cool packs or ice packs covered with a wet hand towel on the chest and abdomen of your dog while it is lying on its side.

5. Never leave your dog in a car , truck, or van, even in the shade and with the windows cracked. Interior vehicle temperatures can reach 150 degrees in 15 minutes on a warm cloudy day. Dogs are in extreme danger when their body core temperature reaches 105 degrees, brain damage occurs at 107 degrees.

6. Keep your crates in the deep shade with the best ventilation possible. Take them out as soon as they show any signs of over heating or physical distress.

7. Never muzzle a panting dog for any reason. If you must restrain your dog do not increase their stress level.

8. Know the signs and symptoms of heat stroke, which steps to take first and how to get to the closest ER vet hospital before your dog is in a life or death situation. Take a certified Canine First Aid & CPR class.

9. Never leave your dog tied out, chained or unattended outside on a hot, warm, warm-humid, warm-cloudy day, as they cannot seek the safety of shade or cool areas on their own.

Heat stroke defined: Heat stroke occurs when your dog cannot cool its body temperature down and their core temperature starts to rise. Your dog is at risk of heat stroke when its core temperature goes over 105 degrees. At 105 degrees core temperature the body systems begin to fail. Brain damage occurs when the body temperature reaches 107 degrees.

Who is at risk? All dogs! Short-muzzled breeds are extremely susceptible, as well as our senior citizen canines, over weight, out of physical condition, and stressed dogs.

Signs and Symptoms
(all signs may not be present at the same time)

1. Uncontrollable panting.

2. Foaming at the mouth.

3. Depressed or lethargic behavior, they may seem weak, stupor like, and have a drunken sailor walk.

4. Unusual levels of agitation and cannot calm down.

5. Either or a combination of vomiting, loss of bowel and bladder control.
Loss of consciousness.

6. Gums and tongue go from bright red to blue or gray as the symptoms get worse.

7. Capillary refill rate is over 2 seconds.

Actions for Survival

(actions should be taken in depending on the severity of the symptoms)

1. Stay calm and clear-headed, think as you react.

2. Restrain without increasing your dogs distress, do not muzzle!

3. Prepare for your dog to go into shock.
Bath your dog’s body with copious amounts of water until its core temperature reaches 104. Avoid the head so that your dog does not breathe water into its lungs. Remember cooling the abdomen is best.

4. Get your dog into a cool and well ventilated space.

5. Place your dog on a cool floor surface, tile or linoleum are great, to reduce their body temperature. Have them lay on their side, if possible. Use cool packs on the abdomen and chest areas, avoid ice directly on the skin.

6. Do not let them eat or drink fluids, this can cause choking.

7. Recheck your dog’s temperature rectally (below 100 and over 104 is an extreme emergency), capillary refill rate and pulse every 5 to 10 minutes during the cooling process.
Transport to the emergency vet as soon as possible.

Dog Norms!

Know your dog’s normal range in vitals before an emergency occurs.

Vitals

Temperature Normal high and low can vary widely, 100.5 to 102.5
Heart and pulse rate 120 to 160 bpm 60 to 100 bpm
Breathing rate 20 to 30 bpm 20 to 30 bpm
Capillary refill rate For all dogs normal is 1 to 2 seconds with pink tissues.
Panting rate For all dogs, up to 200 pants per minute.

Another cooling method:

Keep a bottle of rubbing alcohol with you. Keep it in a mist spray bottle if possible. Spray the bottoms of the feet. This really cools them off. Also keep a portable fan handy. If one gets hot I put the fan on them and spray their feet with alcohol.