As the temperature heats up we find ways to cool ourselves down. Staying hydrated, swimming, shedding outer layers for something thin and light-weight, hanging out in the shade or a cool breeze are great ways to keep body temperature at a comfortable, healthy level for you and your dog. But there are other good ways to promote your dog’s safety and comfort while enjoying the outdoors, and there are signs to recognize when the heat is becoming a safety problem.
A dog’s average body temperature is 101.5 degrees Fahrenheit and the normal range is 100 – 102 degrees. These are core temperature values based on rectal thermometer readings. Temperature can vary throughout the body, but the core temperature is used by the body to maintain homeostasis (i.e. the status quo). Maintenance of that normal temperature range is called thermoregulation. The hypothalamus area of the brain is the temperature command center – the “thermostat.” It regulates body temperature based on readings from hot and cold receptors in the body. Those receptors can be affected by internal conditions like infection and inflammation as well as external conditions like environmental temperature and humidity.
Unlike humans and horses, in times of excess heat, dogs do not do a lot of sweating to reduce core temperature. Instead, they rely on panting to cool themselves. The surface of the respiratory tract is wet and the evaporation that occurs as air passes over its surfaces results in heat loss. A dog’s normal rate of respiration may be 30 – 40 breaths per minute; but when she pants to cool herself, she may breathe as much as 300 – 400 times per minute. Another way a dog cools himself is by diverting blood flow from internal organs toward the surface of the skin. A dog may stretch out on a cool floor or lay belly up to expose more of his skin to dissipate the heat.
When outdoor temperatures climb to high levels, metabolic temperatures can increase. Humidity also plays a role because it reduces the evaporative capabilities of respiratory cooling. During exercise, muscle activity is the primary internal heat producer. Twenty to thirty percent of the energy expended by the muscles is utilized for work while the balance is released as heat. And this heat is normal and helpful. It becomes a problem, however, when other factors – like environmental heat and humidity are elevated.
It’s important to know and recognize the difference between hyperthermia and heatstroke. Hyperthermia is when body temperature exceeds the normal range of 100 – 102 degrees. And as you’ll read shortly, a little elevation outside of this range may not be a problem for well conditioned dogs. Signs that your dog’s core temperature is rising include panting, reducing workload (e.g. laying or sitting down instead of playing, or moving more slowly), settling in cooler locations (e.g. shade or water).
Heatstroke is dangerous and can be fatal. Clinical signs include weakness, loss of balance, confusion, rapid breathing or roaring breath sounds, excessive salivation or thick saliva, collapse, vomiting or diarrhea, tacky or dry gums, change in color of the gums (gums should always be bubblegum pink), bright red tongue, and a high core body temperature (above 106 degrees). Organ failure can begin at 107 degrees so the situation is quite serious.
Breed also plays a role. Dogs with short snouts are more prone to heat-related distress than their long-nose cousins. Any kind of lingering, injury, infection or illness in your dog also can accelerate the problem as these things generally elevate body temperature on their own. Death from heatstroke can happen in as little as 20 minute but these are generally situations where dogs have been left in cars or trapped in greenhouses. And don’t think just because your dog is swimming she’s not at risk. If the water is warm (75° F or above) and your dog is exerting herself a lot, heat related distress and heatstroke can still result.
It’s probably no surprise that overweight dogs are more intolerant of the heat than their lean counterparts. But what about athletic conditioning? Studies have shown that the more physically fit the dog, the more acclimated she becomes to higher core temperatures and the less impact those temperatures have on her. That’s right. Walk two dogs of the same breed and relatively the same size and weight side by side on a summer day, one that is routinely exercised so as to be considered athletic and one that is not, and the unfit dog will be at a greater health risk for overheating and heatstroke than her athletic companion.
Studies of well-conditioned, working, athletic dogs show that they can have body temperatures of 102 – 106 degrees while exercising and not exhibit the signs of heatstroke or distress that would typically be seen in other dogs. The normal resting body temperatures for these dogs can be 99 – 100 degrees and this lower homeostatic temperature is a result of the dog acclimating to routine activity.
Eating the right foods also can help keep dogs cool. In general, the daily diet profile for a healthy dog should be high protein, moderate fat, and low carbohydrate. But on hot days you might want to modify that a bit.
Numerous studies of canine nutrition show that dogs metabolize fat differently from humans – especially during exercise. Studies of racing greyhounds, sled dogs, and even non-sporting beagles have shown that high fat/low carbohydrate diets increase stamina. One of the reasons is that dogs get their energy from fat oxidation during exercise (whereas humans and other less aerobic animals get it primarily from glucose oxidation.) But there’s another benefit to higher fat fuel choices during exercise or periods of higher ambient heat and humidity. And it has to do with the byproducts of metabolism of fat vs. protein or carbohydrates.
One of the byproducts of fat metabolism is water. Proteins and carbohydrates each produce about 55 grams of water per 100 grams burned. Fat, however, produces 107 grams of water for every 100 grams of fat burned. Training a dog’s metabolism to use fat as an energy source may actually benefit the dog’s hydration status.
Another study has shown that dietary fiber may have some health benefits for athletic dogs. Volatile fatty acids produced by bacterial fermentation of soluble fiber in the canine colon promote water and electrolyte absorption.
So if you’re going out on a long hike on a warm day with your canine companion, you might want to choose a fuel for her that’s higher in fat and fiber as a way to help maintain proper hydration and body temperature. Goodness Gracious cookies are a great choice for a healthy balance of protein and fat. Frequent splashes in streams or periods of rest in the shade also are good ideas.
Some breeds, like huskies with their thick coats, are more intolerant of heat than other breeds like Chihuahuas. When the heat becomes oppressive or the humidity makes it feel that way for your particular dog its best to keep things cool and low key. Swimming in cool waters or frolicking around on a shoreline is a good exercise choice if your dog needs to let off some steam, but long walks or running are not. Remember too that pavement, sand and other surfaces heat up. And while you might not feel it through your shoes it could be giving your dog’s paws a serious burn.
If you suspect that your dog is showing signs of serious heat-related distress get her into a cool environment – a cool (not cold) tub of water is great – and call your vet immediately. It’s important to know that excessively cold water or ice can actually cause a decrease or depletion of skin circulation and delay cooling. Also, please remember to keep a look out as you go about your day for other dogs that may be tied up outdoors or stuck in cars. A simple knock on the door of the dog’s home or that of a neighbor, or a phone call to your local animal shelter or animal control officer (generally reached through the police department), can save another dog’s life.
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