Exertional HRI in Dogs

Running gun dogs in the summer can seriously harm them. Here’s how owners can keep them safe

As late spring turns to summer, we all want to shake off the winter doldrums and enjoy the increasing warmth, sunshine and fresh air of longer days. Hiking, biking, kayaking, running or, in the case of sportsmen, conditioning and training your hunting dog or participating in hunt tests and field trials. No matter the activity, rising temperatures present dangers for dogs – both well-conditioned and, especially, those who’ve lived the easy life on the couch since last season’s end.

We all see the headlines every summer; somebody leaves their dog in a locked car and it leads to the dog overheating, bystanders getting involved, citations and more. That type of overheating is known as non-exertional Heat-Related Illness (HRI). It’s brought on when the dog can’t properly cool herself because environmental factors don’t just hinder cooling but exacerbate and compound overheating. Cramped spaces with too little ventilation, such as in a car with the windows up, or even lack of water and shade outside, like in a backyard, can induce non-exertional HRI.

two hunting dogs
Air flow in thick grasses and coverts is low, and can cause dogs to overheat. Eukanuba

However, what we don’t hear about are the countless dogs who suffer HRI issues (heat cramps, heat stress, heat exhaustion or heat stroke) while participating in activities with their owners. In fact, one study suggests that a larger percentage of dogs suffer from HRI issues triggered by exercise than do because of being locked in hot cars. I’ve seen dogs suffer heat-related issues at summer hunt tests in the north and while hunting in Texas during February. A myriad of factors, including not just outside temperature and humidity, but also hydration, nutrition, acclimation, physical conditioning and age, contribute to a dog’s ability to stave off HRI.

How Dogs Deal with Heat

Today’s dogs are uniquely adapted to conserve heat. Nearly every physiological function allows the dog to internalize heat, from the respiratory and cardiovascular systems to the amount and type of hair they have keeps dogs warm with little effort – which was great for dogs’ ancestors living in the wild but presents issues for working and sporting dogs in modern society.

A canine’s body temperature is dependent on a balance between heat inputs from the internal and external environment and the ability of the dog to release that heat.

When a panting dog inhales cold air, he easily expels heat through respiration while dissipating internalized body heat. However, the closer the ambient temperature of the external environment is to the dog’s body temperature, the less effective the dog becomes at cooling itself. If the temperature exceeds the dog’s body temperature, the dog actually begins to absorb more heat from his surroundings. On top of respiration, a dog produces heat through exercise and muscle or metabolic activity. Even metabolizing food will produce heat, which stokes an internal fire that’s insulated by the dog’s body.

Hunting dog takes a rest in the shade.
There always is shade available for break time. Sometimes it’s in your truck’s shadow. Eukanuba

An evolutionary necessity, a dog’s ability to compound heat preservation is actually quite remarkable, especially give the limited ways a dog can release heat. Under normal circumstances, more than 70% of a dog’s total body heat dissipates through radiation and convection; that is, released from the skin into the environment. This is where cool water becomes so important in keeping a dog from overheating – it acts as a heat sink and absorbs the body heat from the dog’s skin. However, as the temperature of the air or water increases, this again becomes less effective.

Because dogs only minimally sweat through their paws and nose, it’s not an effective cooling mechanism when large amounts of heat need to be removed (it’s even less effective if the pads are hard and calloused, as is the case with many sporting dogs). That leaves panting as the primary mover of internal heat into the environment. But, like radiation and convection, as the environmental temperatures increase, the effectiveness of panting decreases. Likewise, when humidity hits 35 percent, effectiveness of panting begins to become compromised, and at 80 percent humidity, it’s nearly completely ineffective

Dogs at Greatest Risk

I abhor comparing dogs to humans, but it’s often the easiest way to get a point across, especially when it comes to exercise issues. Like humans, weight, physical conditioning and acclimation play vital roles in determining whether a dog will suffer heat stress, exhaustion or stroke.

Overweight, out of shape dogs with thick hair or double coats, like retrievers, who have sat on the couch in a balmy 68-degree forced-air living room will have a greater chance of heat-related issues if suddenly expected to run hard and long in hot, humid weather. Chances are, you would too. However, unlike you, who can more efficiently release heat and will likely call it quits before there’s an issue, a dog will keep working, running or playing long after she’s started down the overheating path – and once that process starts, it compounds quickly, becoming harder to stop as the dangers increase and treatment options decrease.

Dog trainer with three gun dogs in the field.
Training in the cool time of the day is best, and usually means getting up pre-dawn. Eukanuba

You can literally run your dog to death.

Even active, well-conditioned dogs are at risk if they live inside. This is where acclimation to working conditions becomes so vital. Dogs must have time to adjust to outside temperatures slowly and consistently. Given time and proper acclimation, they can handle the heat (or cold) better and with less risk. Again, a dog will work in heat or cold until it dies – it’s up to you, the owner, to be mindful of environmental working conditions and provide adequate acclimation, plenty of water, rest periods and shade.

Beyond out-of-shape dogs, young, active dogs and those 12 years of age and older are more susceptible to HRI issues, as are neutered females as compared to intact females. Flat-faced dogs, like boxers or bulldogs, struggle in the heat and dogs with health issues are at greater risk. Interestingly, male dogs develop higher body temperatures than females during intense exercise.

Precautionary Strategies

As always, commonsense and caution are the best rules of thumb when working your dog in adverse conditions. Always err on the side of caution and give your dog the benefit of the doubt. To help keep her safe from heat-related illnesses, know the signs of HRI and take these steps before, during or after work sessions.

Know and Prepare Your Dog

Understand your dog’s natural abilities and what they’re capable of physically – don’t push an out-of-shape dog to work beyond its capabilities. Know your dog’s body condition score and strive for an ideal weight; adjust his feed in congruence with exercise to reach ideal body weight over time. Use a consistent, progressive conditioning program that slowly amps up intensity and duration of activity. Dogs conditioned regularly in April, May and June (sooner in the south), handle hot weather better as they gradually work in increasing temperatures and their bodily systems have time to acclimate.

Account for Environmental Factors

Environmental factors are twofold: you must be mindful of your dog’s normal environment, especially if they spend long periods of time indoors, versus the environment you’re asking them to work hard in. Again, acclimation matters. Second, pay attention to the environment you’re working in; temperature, humidity, sun exposure, water access and terrain. Training in the early morning when the air and ground temps are lowest helps, as does working near and in water. Frequent breaks for swims in cool water will help greatly – the warmer the water, however, the longer the break.

Hunting dog takes a drink of water.
When running dogs in the summer, always make sure you have plenty of cool, fresh water on hand. Eukanuba

Active dogs exercising in the heat must be rested in a cool, shady place with plenty of water every 30 minutes to an hour. To determine if it is too hot for training, add together the actual outdoor temperature and the humidity percentage. If the total is over 140, then avoid outside activities. Example: 75 degrees with 80-percent humidity is 155, which is over the 140 threshold. Alternatively, monitor the heat index and exercise extreme caution if it exceeds 75.

Hydrate Your Dog

Water keeps your dog alive and performing to a high standard. Heavy panting will dehydrate a dog quickly. Ensure your dog has frequent access to water before, during and after work. In hot climates, start increasing water volume between 3 to 5 days leading up to the outdoor activity.

Monitor your dog’s water intake to ensure he’s getting enough. A good rule of them is to calculate the minimum water intake through food consumption. Simply multiply the number of cups of dry food offered daily by three cups. So, two cups of food means the dog should drink six cups of water, and so on. Keep in mind that this target is the minimum amount of water your dog should drink daily when working under adverse conditions. To help increase water intake, add water to their dog dry kibble at a 1:1 ratio and feed immediately so the kibble doesn’t soak up the water. You can also bait water by adding a couple of tablespoons of high-fat canned dog food to their water bowl.

Feed Your Dog

Consider your dog’s diet and caloric intake and balance them against her activity level and environmental conditions. If you’re training hard or will start preseason conditioning in August, consider feeding a performance diet designed for her activity level. It can take a dog’s body 8 to 12 weeks to adapt and train the body systems to use the increase in dietary fat found in performance diets.

Summertime training is a necessity for hunting dogs. There’s no way around it. To safely train and condition your hunting partner, you need to consider your dog’s lifestyle, physical condition and abilities, and use commonsense with plenty of breaks for your dog to cool down and drink water. Knowing the signs of HRI will give you a jump on identifying and treating signs so your dog can safely prepare for the rigors of the upcoming hunting season. Learn more about HRI at eukanubasportingdog.com/HRI.