To Shave or Not to Shave – Based on Science

Hello! What’s it like outside today? Depending on where you are, if it’s winter, it may be cold. If it’s summer, it may be hot. Either way, your core body temperature is probably hovering around 98.6∘F/37∘C. That’s because you’re an endotherm. You use internally generated heat to maintain your body temperature. Body temperature tends to stay steady regardless of your environment. What about our dogs?

We as humans tend to dress differently depending on the season, but what about our dog’s coat? Many [double-coated breeds] wear the same all year round for fear of overheating the dog or disrupting growth. It seems that the science doesn’t exist for a double coated dog but clipping any other breed—of the same species—is less discussed.

It’s summer and you have an appointment with your groomer. “Shave him, he’s so hot,” is often what we hear. What’s the answer to keeping your pet cool? Does anyone really know? Every year this question is asked.

What’s the fastest way to start an online argument?

Ask if a double coated dog should be shaved; cue thermal image of a Golden Retriever in a lion cut.

This is one of the most controversial topics there is in the grooming and veterinary industry each year; whether or not shaving your dog keeps them cooler in the heat (never whether or not to grow them longer for the winter; though, same science applies). This is a persistent dispute with mostly mixed anecdotes and unfortunately little scientific information to be found.

It is imperative that pet owners and pet professionals have an understanding of an animal’s homeostatic temperature mechanism of thermoregulation and the skin and coat before you decide whether or not to proceed with shaving your dog. Only then can you make an informed decision for the individual animal in your care. It comes down to just that, an individual choice based on the animal’s condition and environment.

This Golden Retriever in a lion trim claims that the clipped area is warmer than the long haired area and that it is unspeakable to clip double coated breeds. Of course more heat is coming from the clipped area than the long-haired area. This displays the coat keeping the heat from leaving the body while the clipped area was allowing heat to leave the body more rapidly; a job well done! However, it detects the peripheral microcirculation controlled by the autonomous nervous system, so we don’t know any other factors about the dog in this photo. This parasympathetic element causes the peripheral vasoconstriction of the capillaries nearest the skin, produced by the neurosecretion of catecholamines. It quantifies the skin’s surface temperature based on visualizations of thermographic changes. They detect infrared radiation; the release of surface heat in the form of thermographic images.

Infrared Thermography

Thermal cameras detect infrared radiation and converts the temperatures into images where these thermal emissions can be easily visualized.

When we view an infrared image (thermography) in this case, the image of a dog, it is measuring the heat at the body’s skin surface. These measurements are directly correlated to the circulation in the skin. Temperature data directly correlates to changes within the circulatory, nervous, and musculoskeletal systems. Infrared imaging is actually a very useful complimentary diagnostic veterinary tool in animals.

Thermal Imaging Answered – Veterinary Edition: Everything you wanted to know in video below

A Dog’s Purpose – Skin and Coat

The coat of the dog demonstrates a wide range of not only appearance of colours and patterns at first glance, but textures, lengths, coat types and styles that serve as an important purpose and function of the nature and attributes of that breed’s ideal coat through their history. Eventually, a developed breed standard was developed for the function the dog was bred for.

Nothing has more diversity like canines. Most species look quite similar, but canines—it’s obvious how they can be so different looking, but yet, they are the exact same species. Take a look at the Chihuahua and the Great Dane; the Xoloitzcuintle and the Old English Sheepdog.

The bond and humans’ attachment to dogs goes way back; and as this grew, the practice of breeding dogs also grew increasingly popular as humans realized just how much of a helpful companion a dog could be, so they were purposefully bred. This caused dogs to start looking very different from one another as they were selected for specific purposes that relied on their size, agility, and yes, appearance and more. However, due to socioeconomic changes, the main purpose of today’s dogs are to provide companionship and comfort mainly as a family member. This unique diversity and heritage has been lost. As has the predictable coat type, we now have many combination coats. Often as a result, every coat type ends up being groomed exactly the same. Does this matter? Let’s dissect the integumentary system.

Canine Integument and related structures

The Skin:

The skin is the largest and most visible organ of the body. It is the anatomic and physiologic barrier between the dog and its environment. The skin, hair, and subcutis of a newborn puppy represent 24% of its body weight; these structures constitute only 12% of the body weight by the time a dog reaches maturity.

The skin forms a protective barrier without which life would be impossible.”

Skin provides protection from injuries

  • Physically

  • Chemically

  • Micro-biologically

Its sensory components perceive heat, cold, pain, pruritus (itch), touch, and pressure. Additionally, the skin is synergistic with the animal’s internal organ systems and can reflect pathological processes that are either shared with other tissues or elsewhere. The skin is not only an organ that has its own reactions and patterns, but it is a reflection of interior health and the whimsical world to which it is exposed to. One of the main ways your veterinarian can assess the health of your dog is by looking at the condition of their skin and coat.

General Functions and Properties of the Skin:

  • Enclosing barrier for internal environment for all other organs; maintains an effective barrier to the loss of water, electrolytes, and macro-molecules

  • Environmental protection from external physical injurious and chemical agents

  • Provides bodily motion, flexibility, elasticity and shape

  • Adnexa production – produces keratinized structures such as hair, claws, and the horny layer of the epidermis

  • Temperature regulation: it is skin that plays a role in the regulation of body temperature through its support of the hair coat, regulation of cutaneous blood supply, and sweat gland function

  • Storage: is a reservoir of electrolytes, water, vitamins, fat, carbohydrates, proteins, and other materials

  • Important health indicator: internal disease, and the effects of substances applied topically or taken internally

  • Contributes to physical and sexual identity

  • Immunoregulation

    • Keratinocytes, Langerhans’ cells, and lymphocytes together provide the skin with an immuno-surveillance capability that effectively protects against the development of cutaneous neoplasms and persistent infections

  • Pigmentation: melanin formation, vascularity, and keratinization processes help determine the colour of the coat and skin

    • Pigmentation aids in preventing damage from solar radiation

  • Antimicrobial properties

  • Sensory perception as a primary sense organ for touch, pressure, pain, itch, heat, and cold

  • Secretory organ of the epitrichial (apocrine), atrichial (eccrine), and sebaceous glands

  • Excretory organ

  • Vitamin D production through stimulation by solar radiation

    • While in the epidermis, vitamin D3 (cholecalciferol) is formed from provitamin D3 (7-dehydrocholesterol), via previtamin D3, on exposure to sunlight. The vitamin D-binding protein in plasma translocates vitamin D from the skin to the circulation. Vitamin D3 is then hydroxylated in the liver to hydroxyvitamin D3 and again hydroxylated in the kidney to form dihydroxyvitamin D3. This is important in the regulation of epidermal proliferation and differentiation

Generally the surface of the skin of haired mammals are acidic; canine skin has been reported to range from about 5.5 to 7.5 pH (where in a study, values actually varied at different sites on the skin and varied from day to day.)

layers of the skin

Layers of the Skin:

Consists of three layers:

Epidermis: the outer-most layer of skin; is composed of multiple layers of cells defined by position, shape, polarity, morphology and state of differentiation of the keratinocytes

  • There are four distinct cell types within the epidermis:

    • Keratinocytes: produce keratin, the tough fibrous, waterproof protein that gives skin its resiliency and strength

    • Melanocytes: produce melanin pigment

    • Langerhans’ cells: Found in stratum spinosum; potentially involved in allergic and cell-mediated immune responses in the skin. They are the macrophages of the skin.

    • Merkel’s cells: sensory receptor cells that transmit signals

  • The epidermis is thin, but varies in thickness depending on its location on the body. (two to three nucleated cell layers, not counting the horny layer) in haired skin

For identification purposes, certain areas of the epidermis are classified as layers and are named, from inner to outer:

  • Basal layer (stratum’ basale)

  • Spinous layer (stratum spinosum)

  • Granular layer (stratum granulosum)

  • Clear layer (stratum lucidum)

  • Horny layer (stratum corneum)

Basal Layer

  • Single row of columnar to cuboidal cells

  • Resting on the basement membrane zone that separates the epidermis from the dermis

  • Most cells are keratinocytes, constantly reproducing and pushing upward to replenish the epidermal cells above

  • Melanocytes are regulated by genes and hormones, and stimulated by sunshine or irritation, to produce melanin, which gives the skin its color.

Hypodermis / Subcutaneous Layers of Skin

  • Thick layer of the integument made of loose areolar connective tissue rich with adipose

Spinous layer (stratum spinosum)

  • Epidermal layer; still displays some cell division and contains a large number of Langerhans cells

  • Located in thick and thin skin

Granular layer (stratum granulosum)

  • Epidermal layer

  • Consists of multiple rows of keratinocytes filling with keratin; the nuclei degenerates

Clear layer (stratum lucidum)

  • Layer found only in thick skin

Horny layer (stratum corneum)

  • Outermost layer of the epidermis

  • Outer layer of terminally differentiated keratinocytes that is constantly being shed

Epidermis of Hairy Skinmammals usually consists of three epidermal layers rather than five (stratum basale, stratum spinosum, and stratum corneum)

Dermis:

  • Composed of dense, irregular connective tissue of collagen, elastic, and reticular fibres

  • Includes hairs follicles, nerve endings, glands, smooth muscle, blood vessels, and lymphatics

  • Fibroblasts, adipocysts, and macrophages

  • Two layers: papillary and reticular layer

Papillary Layer:

  • Underneath epithelial layer of epidermis

  • Composed of loose connective tissue and loosely woven fibres and ground substance

  • Dermal papillae assist in cementing the epidermis and dermis together

  • Blood vessels, pain, temperature, and touch receptors are presented

Reticular layer

  • Consists of dense irregular connective tissue

  • Bundles of collagen fibres, from papillary layer blend into this layer

Hypodermis:

  • Permits skin to move freely over underlying bone and muscle without putting tension on skin

Hair

Hair, fur, they are chemically the same thing, from the scientific approach; they are both chemically indistinguishable. If you want to know the difference, they can differ in their growth cycles, their textures, and their grooming needs. Understanding the life cycle of your dog’s hair can help you appreciate investing in better selecting the right tools, products and techniques needed in order to correctly groom the dog presented to you, aesthetically talking.

Hair is made of keratin; which is protein (polymers of amino acids).

Hair and fur fall into two basic genetic categories:

Predetermined length (PDL – Fur)

Undetermined length (UDL – Hair)

Hair is actually the characteristic of mammals. It is important in thermal insulation and sensory perception. It acts as a barrier against chemical, physical, and microbial injury to the skin, which we now know how important skin is. Hair is photoprotective. The coat is important for many reasons and the dog does require some insulation particularly for warmth. However, shaving to the skin is not necessary or recommended for summer comfort. That said, increasing air flow is necessary for efficient heat loss.

According to Muller & Kirk’s Small Animal Dermatology, the ability of a hair coat to regulate body temperature correlates closely with its length, thickness, and density per unit area, and with the medullation of individual hair fibres.

In general, hair coats composed of long, fine, poorly medullated fibres, with the coat depth increased by piloerection, are the most efficient for thermal insulation at low environmental temperatures. Coat colour is also of some importance in thermal regulation;

  • Light-coloured coats are more efficient in hot, sunny weather

  • The glossiness of the hair coat is important in reflecting sunlight

  • Transglutaminase is a marker of early anagen hair follicles, and it is important in the protein cross linking that contributes to the shape and remarkable physical strength of hair

  • The diameter of the hair shaft is largely determined by the volume of the hair matrix epithelium, and the final length of the hair shaft is determined by both the rate of hair growth and the duration of anagen

Hair Coat Types

Hair types in dogs are extremely diverse. You will find various authors have attempted to classify them on the basis of colour, length, and other characteristics, Muller & Kirk’s Small Animal Dermatology divides dog hair types into normal (intermediate length), short, and long coats.

Normal Coat

  • Seen in the German shepherd, the Welsh Corgi, and wild dogs such as wolves and coyotes

  • Composed of primary hairs (coarse guard hairs or bristles)

    • And secondary hairs (fine hairs or undercoat)

Short Coat

  • Classified as coarse or fine as seen in the Rottweiler and many of the terriers

  • This type of coat has a strong growth of primary hairs and a much lesser growth of secondary hairs

  • Total weight of hair is lower, and the secondary hairs weigh less and are fewer in number than those in the normal coat

  • Fine short coat is illustrated by Boxers, Dachshunds, and Miniature Pinschers.

    • This type of coat has the largest number of hairs per unit area. The secondary hairs are numerous and well developed, and the primary hairs are reduced in size as compared with those of the normal coat

Long Coat

This can be arranged into two subdivisions: the fine long coat and the woolly or coarse long coat.

The Fine Long Coat

  • Found in the Cocker Spaniel, the Pomeranian, and the Chow Chow

  • Has a greater weight of hair per unit area than does the normal coat, except in the toy breeds (which the weight of the hair may be less because it is finer)

  • The woolly or coarse long coat is found in the Poodle and in the Bedlington terrier and the Kerry blue terrier

  • Secondary hairs make up 70% of the total weight of these coats and 80% of the number of hairs; compared with other secondary-type hairs, these are relatively coarse

  • These breeds (above) have less tendency to shed hair than do many breeds. The genetic aspects of coat colour in dogs are said to represent a complex issue

  • Pigmentation in individual hairs may be uniform throughout the length of the shaft, or it may vary

Hair Follicles

The growth of hair occurs within hair follicles in a sequence of stages.

The hair shaft is divided into:

Medulla

  • The innermost region of the hair

  • Composed of longitudinal rows of cuboidal cells/cells flattened from top to bottom

  • The cells are solid near the hair root, but the rest of the hair shaft contains air and glycogen vacuoles

Cortex

  • The middle layer

  • Consists of entirely cornified, spindle-shaped cells; long axis is parallel to the hair shaft

  • Cells contain the pigment that gives the hair its colour

  • Pigment may also be present in the medulla, but it has little influence there on the colour of the hair shaft

  • Accounts for one-sixth to one-third of the width of the hair shaft

  • Contributes the most to the mechanical properties of hair fibres

Cuticle

  • The outermost layer of the hair

  • Formed by flat, cornified, anuclear cells arranged like slate on a roof; the free edge of each cell facing the tip of the hair

  • Secondary (“down”) hairs have a narrower medulla and a more prominent cuticle than primary hairs, and “lanugo” hairs have no medulla

Follicles:

  • Usually positioned at a 30- to 60-degree angle to the skin surface

  • Dogs have a compound hair follicle arrangement; a cluster consists of two to five large primary hairs surrounded by groups of smaller, secondary hairs

  • One of the primary hairs is the largest (central primary hair), and the remaining primary hairs are smaller (lateral primary hairs)

  • Each primary hair has sebaceous and sweat glands and an arrector pili muscle

  • Secondary (down) hairs may be attended only by sebaceous glands

  • Primary hairs generally surface by themselves through separate pores;

    • The secondary hairs appear through a “common pore”

      • Anywhere from 5 to 20 secondary hairs may travel each primary hair

  • Has five major components: the dermal hair papilla, the hair matrix, the hair itself, the inner root sheath, and the outer root sheath.

If you look at a strand of hair, the visible hair above the skin is called the shaft.

  • Below, you have the root of the hair. Each hair is secured by the hair follicle, while the deepest part of the hair follicle forms a hair bulb

  • The papilla is at the base of this bulb, it is covered with rapidly dividing epithelial cells (the matrix)

  • These cells need to be nourished by blood flow from the vessels under the papilla. The nourishment stimulates even further cell division and growth. As these cells divide, older cells are “pushed” up into the passageway. As they lose contact with their provided nutrition, these cells become keratinized; dying and becoming a part of the developing hair. The root hair plexus is a web of sensory nerve endings in the root. This makes it an important receptor to touch when the hair is bent or folded

Hair follicle

Hair Cycle

Hairs do not grow continuously, but rather, in cycles.. Each cycle consists of a growing period. Factors that may control or influence the growth of hair have complicated the analysis due to the evolutionary history of the dog.

  • Anagen: the follicle actively produce hair

  • Telogen: resting phase; the hair is retained in the follicle as a dead (or club) hair that is subsequently lost

  • Catagen: transitional period between previous two stages

    • It is often stated that certain breeds of dogs, such as Poodles, Old English Sheepdogs, and Schnauzers, have continuously growing hair coats, but there has been no scientific investigation that would support this. (i.e. UDL)

The relative duration of the phases of the cycle will vary. This includes:

  • Due to the age of the individual

  • The region on the body

  • The breed of the dog, and

  • Even with the gender

Additionally, it can be modified by a variety of physiologic and pathologic factors.

Hair coats and the hair cycle are controlled by photoperiod, ambient temperature, nutrition, hormones, all around general state of health, genetics, and lastly poorly understood intrinsic factors. These may include growth factors and cytokines produced by the follicle, the dermal papilla, and other cells in the environment.

Canine hair growth cycle

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 hair coat. Severe illness or systemic stress can cause many hair follicles to enter synchronously and sharply 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.

The hair cycle and hair coat can also be affected by hormonal changes.

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.” Muller & Kirk’s Small Animal Dermatology

  • 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

Therefore, the answer to: Will my dog’s coat grow back? or in the rare instances they don’t – this is due to underlying conditions or pre-existing medical issues and not due to shaving a dog’s coat.

Sweat Glands Suoriferous glands – How do Dogs Sweat

Footpads

The canine footpad is a specialized area of integument.

  • Thick epidermis

  • Protects against trauma

  • Many atrichial sweat glands produce a secretion that actually improve traction during activity and important in scent marking

  • Large fat deposits provide shock absorbing elasticity

  • Provides generous amount of nerve supplies

  • Provides an important sensory function

Sweat Glands Suoriferous glands

There have been analyzes into the physiology and ultrastructural aspects of sweat production according to Muller & Kirk’s Small Animal Dermatology, and it has been suggested that the apocrine and eccrine sweat glands be more accurately called the epitrichial and atrichial sweat glands.

Apocrine Epitrichial Sweat Glands

  • Are generally coiled and saccular or tubular and are distributed throughout all skin that is haird

  • These are NOT present in footpads or the nasal planum

  • These glands are located below the sebaceous glands in the skin, and they usually open through a duct into the pilary canal in the infundibulum, above the sebaceous duct opening

  • Tend to be larger in areas where hair follicle density is lower i.e. largest and most numerous near mucocutaneous junctions, in inter-digital spaces, and over the dorsal neck and rump

  • Consist of a single row of flattened to columnar epithelial (secretory) cells and a single layer of fusiform myoepithelial cells

  • Lined by two cuboidal to flattened epithelial cell layers and a luminal cuticle but no myoepithelial cells

  • Do not appear to be stimulated but rather, has pheromonal and antimicrobial properties (IgA content)

  • Enzyme histochemical studies have demonstrated alkaline phosphatase and acid phosphatase in epitrichial sweat gland secretory epithelium

Atrichial (merocrine) Sweat Glands

  • Found only in the footpads; excretory duct opens directly to the footpad surface

  • Glands are small and tightly coiled

  • Located in the deep dermis and subcutis of the footpads

  • Secretory coils consist of a single layer of cuboidal to columnar epithelial cells and a single layer of fusiform myoepithelial cells

  • Intradermal portion of excretory duct consists of double row of cuboidal epithelial cells

Sweating and Thermoregulation:

Dogs do have sweat glands, yes. Believe it or not, dogs do sweat. So what’s the real science on this? Dogs’ skin does not hold the capacity of the superficial arteriovenous shunts that swine or of us humans feature to circulate heat in hot weather.

The mechanisms of frequency of sweating and the conditions dogs dissipate heat remains ill-defined and a subject left for science yet to define.

“The problem of temperature regulation in dogs and cats 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.” -

Muller & Kirk's Small Animal Dermatology Tweet

Regulating Temperature:

Will shaving keep my pet cool, or am I doing more harm than good? Yes or No

Homeostasis

Homeostasis refers to the relatively stable state inside the body of an animal. Animal organs and organ systems constantly adjust to internal and external changes in order to maintain this steady state.

General Principals:

A feedback system – this is a cycle of events in which information about the status of a controlled condition which is continually monitored and fed back (reported) to a central region

• Any disruption that changes a controlled condition is called a stimulus

Feedback Systems:

Negative Feedback System: if a response reverses the original stimulus (most common in the mammalian body)

Positive Feedback System: if a response enhances the original stimulus

Examples of internal conditions maintained homeostatically are

• The level of blood glucose

• Body temperature

• Blood calcium level

These conditions remain stable because of physiologic processes that result in negative feedback relationships.

When homeostatic mechanisms fail, the results can be harmful for the animal. Homeostatic mechanisms keep the body in a dynamic equilibrium by constantly adjusting to the changes that the body’s systems encounter. Even an inactive animal is maintaining this homeostatic equilibrium.

Another example of factors that are regulated homeostatically are temperature (and the water content of the animal). The processes that maintain homeostasis of temperature and important in this feature is thermoregulation.

The goal of homeostasis: to maintain equilibrium around a specific value of some aspect of the body or its cells, called a set point. There are normal fluctuations from the set point, but the body’s systems will usually attempt to go back to this point.

A change in the internal or external environment is called a stimulus and is detected by a receptor; the response of the system is to adjust the activities of the system so the value moves back toward the set point.

Thermoregulation

Thermoregulation: despite fluctuations in temperature of the external environment, the ability of an endothermic organism to maintain a relatively constant body temperature. This is a vital part of homeostasis

You’ve probably heard the [outdated] phrases “warm-blooded” and “cold-blooded”. We can divide animals into categories, depending on how they regulate their temperature.

In the face of differing environmental temperatures, some animals maintain a constant body temperature while others have a body temperature that is the same as their environment and varies.

*Homeotherm: animals that maintain a constant body temperature in the face of environmental changes

Ectotherms:

• Animals that do not control their body temperature

• They rely on external energy to dictate their body temperature

• Formally known as “cold-blooded”, but the term may not apply to an animal in the desert with a very warm body temperature

Endotherms: *dog

• Animals that rely on internal sources for body temperature and can exhibit extremes in temperature

• Are able to maintain a level of activity at cooler temperature, which an ectotherm cannot due to differing enzyme levels of activity

Poikilotherms

• Animals with constantly varying internal temperatures

Dogs are endotherms. They have specific physiological adaptations for regulating their body temperatures.

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

Come back next year as I’m sure the science will have changed!

Synergistically Yours,

Danielle & Sheepdog Riggs

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