Heat Stress in Hunting Dogs

by Delores E. Gockowski, DVM

What canine is more genetically motivated and chase-persistent than the hunting dog? In hot weather, this warrior mentality can end a dog’s life quickly if owners don’t recognize the subtle signs of heat stress early.

Heat stress is a combination of the heat, humidity, strenuous exercise, the inability to sweat and dehydration. Risk factors include age extremes (young and geriatric dogs), thick hair coat, lack of conditioning, stress and a prior history of heat-related illness.

HEAT and HUMIDITY

It is not the heat alone, but the heat and the humidity that sets the stage for heat stress. A quick method to calculate heat stress is to add the environmental temperature (in °F) to the percent of humidity. If this number is greater than 150, watch your dogs for signs of heat stress. If the number is 180 or greater, this is a RED ALERT and your dog risks heat exhaustion or heatstroke. In humans, heat stroke may follow the day after heat exhaustion and is referred to as the 1-2 punch.

LACK OF CONDITIONING

Athletes train for months before competition. Likewise, hunting dogs are conditioned two to three months before the season to build endurance and prevent injury. Dog owners learn to read their individual dog’s physical and mental fitness during the training phase. Some dogs can and will run until the end. Others stop whether it is due to genetics, poor conditioning or health problems.

During the training phase, nutrition is adjusted based on body condition. The amount fed depends on the quality of the food, the dog’s energy level and body condition. The goal is to build lean muscle and decrease body fat. The over-conditioned dog is a poor endurance candidate. High fat and protein and low carbohydrates are the basis of performance diets. A high quality protein should be the first ingredient on dog food label. Fats are energy-dense and supply more than double the calories of protein and carbohydrates. Most commercial diets have adequate vitamins and minerals, but some hunting dogs may need supplemental antioxidants and vitamin E to prevent work related cell damage. Digestion requires increased blood supply to the GI tract; the same blood supply needed for muscle function during a run. Schedule feeding 2-3 hours before or after a run, decrease the amount fed, and offer water after the dog has cooled down.

When you know your job and the routine to get there, the day is less stressful. Dogs need to be acclimated to transport and the environment they will work in. Hunting in locations where the environment is different can put your dog behind the eight ball. Dogs should readily accept the ride and you should plan for minimal stops before your destination or if a long drive, plan for multiple rests especially during hot weather. Offer fluids before and after transport. Decrease mental anxiety by preventing competition and aggression by other dogs. Following a run, don’t immediately place heat-stressed dogs in transport until they have recovered. There is a misconception that wind will aid in cooling. Only after the dog has been re-hydrated, will a cool breeze be beneficial and then it should be less than 80F. At home, provided a shaded or sheltered area with a breeze or ventilated kennel. Ground surfaces should be selected to help to dissipate body heat. Keep fresh water available at all times.

Dogs can’t sweat to remove excess heat. They pant and increase breathing rates, but these are inefficient cooling processes. They may salivate leading to electrolyte loss and dehydration. Performance may decline, but they will be on a run, out of your sight and still determined to keep moving. Panting, increased breathing rate, salivation and decreased performance are the first subtle signs that heat stress is occurring. It is important to offer fluids before and after a run, but don’t over-hydrate. A rule of thumb to determine how much your dog should drink before a run is for every 10 ponds of body weight, a dog should drink 1 ½ ounces. A 50–pound dog needs about 1 cup of water. A squirt-bottle can be used to help measure or limit how much your dog drinks. Before a dog will drink voluntarily, 6% of their body weight can be lost. Compare pre-run and after-run weights to know how your dog is handling the heat. If dogs refuse water consider bringing water from home or flavoring it with a “soup cube”. Commercially prepared powdered electrolyte solutions, like Tech-Mix’s K-9 Restart™ or K-9 Bluhte™ are good choices as they can be added dry to food or mixed in water and easily transported.

HEAT EXHAUSTION and HEAT STROKE

As heat stress progresses to heat exhaustion, the dog’s heart rate, breathing rate and body temperature continue to increase and they may act disoriented (failure to respond to commands, staring or anxious expression). The dog may vomit or experience diarrhea if fed recently. Heat exhaustion can develop several days after exposure to high temperatures and lack of water.

A rectal thermometer can quickly tell if the dog’s normal temperature (102F) has been exceeded. The palm of your hand held on the chest behind the elbow can give you a heart rate. The key is to know the resting rates of your dog before the run and compare it to the rate right after the run. When a dog shows signs of heat stress it is important to cool the dog FIRST, then give oral fluids. Cooling can be done with a garden hose or submerging in cool, not ice cold water. Wet the dog, then massage the dog to remove the water and repeat applying the water until panting decreases significantly. Concentrate cool water on the hairless areas of the abdomen and hind legs to speed the cooling process. Ice paks can be used in an emergency. Monitor rectal temperature and stop cooling before body temperature reaches a normal range. Offer only small amounts of electrolyte water or water as too much volume results in vomiting, which results in more dehydration. If the dog isn’t responding, transport to a veterinarian immediately.

If heat stress is not recognized or treated promptly, heatstroke, the most serious of heat related illness results. This is a veterinary emergency. Convulsions or collapse follows severe fatigue and muscle weakness. At this point, cool water-cooling is not recommended as the dog’s peripheral blood vessels are constricted and cannot allow heat loss. Dogs cooled below normal body temperature and in comas have a lower chance of survival. In running dogs, muscle tissue is being broken down and the by-products result in kidney failure that may not be evident for 48-72 hours. Internal organ damage begins at 107.6F resulting in multi-organ failure including the brain, liver, kidney, blood and muscle.

Any dog showing signs of heat stress needs days to weeks to recover and they will always be more prone to heat stress injury.

PREVENTION is the key to prevent heat-related illness. Be aware when temperatures soar and humidity is high. Pre-condition dogs with good nutrition and exercise programs. Remember the value of water before and after the hunt. If you are having a difficult time with the heat, your dog likely will, too. Unfortunately, your dedicated hunter won’t always tell you until it is too late.

Dr. Gockowski owns North Ridge Veterinary Service, LLC, a mobile mixed animal veterinary practice based in Sturgeon Lake, MN.

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