To Shave or Not to Shave – Based on Science

This means dogs maintain a fairly constant body temperature of 101 to 102 degrees, according to James H. Jones, an expert in comparative animal exercise physiology and thermoregulation at University of California at Davis. “The trick to being a homeotherm is to be able to adjust internal heat gain and heat loss. . .in order to maintain a constant body temperature.”

Homeotherms use behavioral thermoregulation (i.e., habitat choice) to adjust their body temperatures. However, (unlike a poikilotherms), they do not depend solely on the outside environment as a source of body heat. Rather, homeotherms use physiological mechanisms to regulate their body temperatures independently from ambient temperatures.

Homeothermic animals, such as dogs, increase heat production to maintain body temperature at low ambient temperatures. The ambient temperature below which heat production starts to increase is termed the lower critical temperature and appears to vary with the thickness of an animal’s coat (Scholander et al., 1950b). Metabolic rate also increases in homeotherms in high ambient temperatures because cooling mechanisms require energy. The temperature above which energy consumption increases is the upper critical temperature. The range of temperatures at which normal temperatures are maintained with no increase in metabolic rate is the thermoneutral zone. (NRC 2006).

The Thermal Neutral Zone:
• Normal range of temperatures at which a species can maintain their body temperatures without expending energy to increase heat production or heat loss
• In dogs, this is 68-86F (20-30C)
• Coat thickness and other specific breed or individual properties will affect the upper and lower critical temperature zones
• When a dog’s temperature rises above this UCT, hyperthermia is the result (increased body temperature along with other symptoms).
• When a dog’s temperature drops below the LCT, hypothermia is the result

Thermoregulatory Mechanisms of Action

All thermoregulation mechanisms are designed to return the body back to homeostasis. Animals have body structures and physiological responses that control how much heat they exchange with the environment.

Body temperature is controlled by thermostatic mechanism in the anterior hypothalamus, known as preoptic area, which is the main organ responsible for thermoregulation and keeping the balance between heat gain and heat loss. Changes in ambient and internal temperature are conveyed from peripheral and central thermoreceptors to the thermoregulatory centre. As dictated by the thermostatic temperature setting or set point, the appropriate physiologic responses to heat loss or heat gain is initiated.

The body is affected by four processes of heat transfer: Radiation, Evaporation, Convection and Conduction.

Thermal Radiation

• Natural process of the body releasing heat into the environment

◦ Less effective when ambient temperature reaches body temperature

• Emission of electromagnetic “heat” waves

• Heat comes from the sun in this manner and radiates from dry skin the same way

Evaporation

• Endothermic process of a fluid changing to a vapour

• Heat can be removed with liquid from a surface

• This occurs when a mammal sweats

• In sweating, glands in the skin release water containing various ions

• A dog pants, breathing rapidly and shallowly with its mouth open to increase evaporation from the surfaces of the mouth; one of the most important ways a dog thermoregulates

◦ Most effective when the ambient temperature reaches 89.6°F (32°C); less efficient with high ambient humidity, which increases the risk for  heatstroke

Convection

• Currents of air remove heat from the surface of dry skin as the air passes over it; as seen with use of a fan or with wind

Conduction

• Heat will be conducted from one surface to another during direct contact with the surfaces, such as an animal resting on a warm rock

Mechanisms to Conserve Heat

When the environmental temperature falls, the body attempts to reduce heat loss by vasoconstriction in the skin. To improve the insulating qualities of the skin and coat, the hairs stand upright (piloerection). Critical temperature is what is known at which heat production has to be increased and the external temperature at which the heat-retaining mechanisms are no longer able to maintain a constant body temperature. Normal dogs with intact pelage have a critical temperature of 14°C (57°F); when their coats are shaved off, however, they have a critical temperature of 25°C (77°F). Thick subcutaneous fat also acts as efficient insulating material.

Non-fasting animals have a lower critical temperature than fasting individuals; consequently, the latter are better able to tolerate a low environmental temperature. When the mechanisms of heat conservation are no longer effective in preventing a fall in body temperature, an increase in heat production begins. A rapid increase in heat production is accomplished primarily by shivering. Shivering begins when the rectal temperature falls 1°C in normal dogs.

Mechanisms to Dissipate Heat

Heat is regularly lost from the body by radiation, conduction, and convection (75%); the efficiency of these mechanisms varies with the external temperature and humidity, and it is modified further by the animal’s vasomotor and pilomotor responses. At higher temperatures, these responses become ineffective, when heat loss by vaporization of water from the dog’s skin and lungs becomes more influential. Dissipation also occurs through the vaporization of water from the skin and respiratory passages; and excretion of urine and feces. Though, the excretory losses are relatively unimportant in heat dissipation.

Dogs do not produce an abundance of atrichial sweat as we discussed, they have developed the ability to vaporize large volumes of water from their respiratory passages. If the environmental temperature rises above 27° to 29°C (81° to 84°F), the rate of breathing also rises, but the depth of breathing (tidal volume) is markedly reduced. This assists in preventing excess carbon dioxide blow-off and severe blood gas changes.

At a rectal temperature of 40.5°C (105°F), the dog is in danger of a thermal imbalance; at 43°C, collapse is impending.

The trouble of temperature regulation in dogs is often complicated by the physical condition of the coat and by the environmental temperature. Breeds with heavy coats intended for cold climates sometimes suffer when they are moved to regions of high temperatures. The problem is greatly accentuated by a matted, unkempt coat that stifles air circulation through the hair. Proper grooming greatly increases the comfort of these animals.

How to Groom Your Dog for the Summer Heat

This comes back to doing what is right for the individual dog and its environment. Always maintain regular grooming. Fur actually insulates the body very well in cold weather while aiding in preventing the body from taking on too much heat in the warmer weather as a thermal regulator to slow down the process of heat absorption. Dogs can make their coats more suited for hot weather and protection from the heat by shedding appropriately and maintaining the outer layer. No drastic measures like shaving need to be taken.

While dogs are highly adaptable creatures, acclimation does takes time. Moreover, one of the most obvious results of climate change is that environmental temperatures are changing at a fast rate and adaptive thermoregulation in endotherms may alter responses to climate change. 

Acclimatization time should be planned, as small animals can require from 10 to 20 days to adjust; full acclimatization takes 60 days for when changes in ambient temperature are expected to occur.

Special care should be taken with puppies, geriatric dogs, and ill animals as they have a reduced capacity to maintain their body temperature (NRC, 2006).

Some dogs may benefit from a thorough grooming, though, fully shaving a dog is not usually necessary unless neglected and there is matting involved. Keep your dog on a 4-6 week schedule at the professional groomers to maintain the coat, while providing maintenance brushing at home. All breeds can benefit from brushing.

If you’re tempted to shave your dog with a thick double coat, these breeds naturally thin their undercoats during warmer months. When regular grooming is kept up, this isn’t a problem. Grooming is just one factor in keeping dogs cool during the warm winter months.

What can you do instead?

An animal’s coat is there to protect the animal. The skin and coat is the outermost layer of the animal, and serves as a barrier to protect the animal from its environment, including temperature, but as we have witnessed, it does pose restrictions. The coat has insulating functions when properly maintained.

• All dogs, regardless of breed or hair coat type can benefit from regular professional grooming at 4-6 week intervals

  • This provides proper skin and coat stimulation for proper growth

  • For shedding dogs, shaving does not eliminate shedding, but rather, reduces the length of the hairs seen shed

  • As hair is predominantly protein, nutrition has a profound effect on its quantity and quality; a balanced, appropriate diet is important. Without adequate diet, the coat may become dry, brittle, weak, and fall out (increases shedding)

• In order to keep our pets cool in the heat, take the same precautions as you would for yourself:

  • Don’t overwork the animal

  • Exercise dogs only during cooler periods of the day

  • Keep them in the shade and out of direct sunlight

  • Always provide plenty of fresh water

• Make sure the skin and undercoat is groomed out and the coat is properly maintained – all year round

• Never leave dogs alone in closed vehicles (even with “fobs” your vehicle could malfunction)

• Acclimate dogs to warm temperatures for up to 2 months

• Take precautions/Surgically address upper airway obstructions, such as brachycephalic airway disease or laryngeal paralysis

What’s My Risk (Double Coated Breeds) Risks of Coat Not Growing Back

There is a very small risk of abnormal re growth in dogs with underlying health conditions if they are ill and not because of the clipping itself. Under conditions of a dog that has ill health or generalized disease, anagen phase may be considerably shortened; accordingly, a large percentage of body hairs may be in telogen at one time. Disease states may also lead to faulty formation of the hair cuticle, which results in a dull, lusterless hair coat. Severe illness or systemic stress can cause many hair follicles to enter synchronously and aggressively into a telogen shedding of these hairs (telogen defluxion) which occurs simultaneously and can result in a visible thinning of the coat or actual alopecia.

“Hair growth is a confusing subject that needs much research. It should be remembered that the haircoat of pet animals is a cosmetic or ornamental feature. Every effort should be made to minimize procedures (clipping and shaving) that may affect the animal’s appearance for many weeks.”

• Normal or short coats usually take about 3 to 4 months to regrow after shaving

• Long coats may take as long as 18 months

• On occasion, an unexplained and discouraging failure to regrow hair in an area of skin can occur usually following clipping

Post-clipping Alopecia

Failure to regrow a dog’s coat following clipping has been termed post-clipping alopecia, or follicular arrest. This means the hairs may not regrow for up to 24 months, but they usually regrow within 1 year. Although this condition has been described as relatively common, the authors of Muller & Kirk’s Small Animal Dermatology consider it uncommon in their clinical experiences and discussion with groomers and veterinary surgeons. Although it is seen more often in breeds with long, thick coats, such as Siberian Huskies and Chow Chows, it can occur in any dog that is not double coated.

The condition is most commonly seen following clipping for surgical procedures or in severe neglect cases for the removal of matted and pelted coats. Many worry about clipping their double coated breeds to relieve them from the heat for fear of post clipping alopecia.

It has been projected that this syndrome may occur as the result of “vascular perfusion changes in response to cutaneous temperature changes.” Another possibility, however, is that these dogs are in their normal catagen stage of hair growth, between losing and growing a new hair coat. This theory is supported by the histologic changes in biopsies from normal-haired and affected areas; both can show catagen arrest. Most of these dogs do regrow hair in the clipped area after they go through a heavy shedding, or rather, “blowing of their coat”.

An acquired alopecia, however, is a hair loss that develops sometime during the life of the dog. There are also hereditary alopecias and hair losses that develop as a result of specific disease processes, such as

• Dermatophytosis

• Endocrine abnormalities

• Immunologic diseases,

• or self-inflicted hair loss from a hypersensitivity or parasitism.

Whatever the cause, many are poorly understood.

Hereditary follicular dysplasia is also well known among certain breeds, including Siberian Huskies (again, double coated breed) suggesting a genetic basis. There are several endocrine syndromes (adrenal sex hormone imbalances) in addition that may also have abnormalities in follicular receptors, signalling a component of the disease that may be considered a dysplasia. These syndromes also have predisposed breeds,such as the Pomeranian, the Samoyed, and the Chow Chow – also all double coated breeds among the “thou shalt not shave” list. That’s not to say non-predisposed breeds also develop similar findings.

Clinical findings in these dogs include:

• Poor, dry, frizzy hair coats;

• Changes in coat colour

• Loss of primary hairs and retention of secondary hairs

• Development of curly or twisted hairshafts

• Varying degrees of alopecia

• Failure to regrow their coat following clipping

• Cases of dogs were typically clipped because of a poor or dull coat that the owner believed would improve with new growth after clipping