My dog will not get hot if I remove his coat – Fact or fiction

Spring has sprung here in Australia and the forecast is for a hot spring and summer with reduced rainfall. Groomer’s telephones have started ringing with clients needing appointments to “take off the matted long hair my dog has been carrying over winter, so that he will be cooler”

But is a dog actually cooler or not when they are shaved down? Should dogs be allowed to develop heavily matted pelts during winter that are never brushed and then put into a boom or bust scenario during the hotter months? Do we shave Shih Tzu’s and Maltese off to make them cooler or just to make them easier to maintain?

Dogs come in a multitude of shapes, sizes and colours; they also have different grooming needs.  What they don’t vary in is that they are susceptible to heat stroke and get matted if not brushed effectively.

Humans cool by producing sweat from our biggest organ, the skin. We perspire and cool by the evaporation of this perspiration as air moves across our skin. The human body controls temperature regulation using the sweating centre located in the part of the brain called the hypothalamus. This centre stimulates the sweat glands to release sweat and for each gram of sweat that evaporates half a calorie of heat is dissipated¹.

Dogs however have a panting centre which stimulates panting. Panting is rapid sallow breathing that causes air to be passed through the nose and over the tongue allowing efficient evaporation to occur. The tongue has a rich blood supply and heat produced in the muscles and tissues enters the blood and is transported to the tongue. A dog’s nose maximizes this process due to its many tissue folds that increase the surface area the air can come in contact with. This tissue also perspires and has a large blood supply, so like a car radiator, body heat is reduced. Air is brought in via the dog’s nose and then exhaled through the mouth and it picks up moisture and heat from the nose, thereby cooling and drying it. Exhaling through the mouth where there is less blood supply and a lesser surface area, results in almost all of the moisture being absorbed and heat leaving the dog’s mouth via to the surrounding air. When he no longer wishes to lose body heat he exhales the air brought in via the nose back out the nose. This causes a greater proportion of moisture and heat to be returned to the large surface area in the nose thereby minimizing heat loss.¹

Dog’s also have a spleen that is much larger relative to its body size than a human. The spleen stores blood and during exercise it contracts, releasing blood into the blood stream. This extra blood is then available to carry more heat to the tongue for removal. This is what gives dog’s much better endurance than people.

Dogs do have sweat glands in their feet and ears, however they are inefficient and play a very small role in thermoregulation. A dog’s fur also acts as insulation both against heat and cold, functioning much like the insulation in the roof or walls of your house. It keeps in warm air and cool air as required. Their skin has more than one hair growing through each follicle with a guard hair that is normally longer than the others. Dog’s can piloerect (raise these guard hairs) by contracting or lengthening muscle fibres. The dog’s hair insulates against cold and heat with degree of insulation increasing with fur thickness. The natural seasonal shedding in summer and winter is the dog’s natural way of dealing with the amount of hair required to cope with winter and summer temperature demands if the dog is kept well groomed.   Kittens and puppies are born as cold blooded animals and if shortly after birth they are removed from their surroundings will rapidly lose body heat, hence mother dogs and cats will snuggle with their babies for long periods up until they develop coat.   Dog’s also utilise behavioural adaptations to handle heat, resting in the heat of the day and being more active at dusk and dawn. So let’s say we decide to clip off a Border collie or Belgian shepherd what happens to its ability to deal with heat?   Biophysics in the form of Newton’s law of cooling provides a formula for measuring temperature at the tip of a hair and temperature at the surface of the skin. It can estimate the ability of a hair to conduct heat. ²   Most mammals attempt to keep their skin at about 85^oC (29^oC).The sun can heat the tip of a hair to more than 150^oF (66^oC). Using the formula for Newton’s law of cooling (see the full articlefor the details) it can be determined that if a dogs hair is six inches long the number decreases however if the dog’s hair is clipped to 1 inch then the number rises with a higher number meaning increased heat at the dogs skin. Therefore a dog with longer hair will have less heat at their skin than a dog with shorter hair i.e. the hair insulates. If you surgically clip with a very short blade such as a 10 or 30 the number becomes dangerously high. Hence many groomers will attempt to find a happy medium between clipping short and clipping off half the length of the coat with snap on combs. If the dog’s coat is heavily matted and the night time temperature decreases then the dog will be losing skin heat i.e. becoming hypothermic. A matted coat impedes the dog’s ability to vary the length of the hair (piloerection) and the mats also alter the dog’s ability to dump heat from their skin surface to the outside air, thereby causing hyperthermia. Exercise makes this situation even worse. When dog’s are suffering from heat stress they are soaked in tepid water which makes the hair more conductive to temperature, and also flattens the coat, allowing body heat to be dissipated more rapidly thereby reducing the core temperature of the dog.

Many owners will state that they think their dog feels better after a clip as they see them running around. I posed this question to a number of American master groomers via the Groomers email list at Groom-TNT, the largest international professional pet grooming E-mail network in the world. Barbara Bird, Certified Master Groomer, recognised at a leading groomer educator worldwide summed this up nicely

“As to the matter of the dog running around and seeming to feel better after clipping, we have no comparison of how the dog might “feel” after a professional deshedding and removal of the excess shedded undercoat.

In the US, a growing number of groomers are declining to do shave downs on double coated breeds, or will do them only when the owner signs a release form that states that they are aware of the possible outcomes and agree to hold the groomer harmless in the event of poor regrowth, sun damage, or heat related episodes”

I also posed the question to a facebook site on which many experienced animal behaviour observers comment on behaviour and the speculation was that the zoomies seen after a grooming session are actually more a stress relief reaction to how different a dog feels once the coat is removed rather than what owners see as a reaction in which the dogs are “running around because they feel cooler”

Do I clip off my black Belgian Shepherds when we get consistent temperature over 30^oC in summer?

No I don’t but I do try to ensure they have well groomed out, dematted coats and plenty of drinking water and a cool place to lie. I do some clipping for my very old dogs to remove some coat weight around the britches and sanitary area to allow the dog to lie on a cool damp place as  most older long haired dogs normally have a great deal of coat build up in this area. I also refuse to clip off dogs that I believe will be adversely affected by the process, no matter how much the owner attempts to persuade me otherwise. As a scientist I have now examined too much scientific information that I believe points to this practice being detrimental to our canine companions.