Dog coat

{{Short description|Hair that covers a dogs body}} {{About|a dog's natural fur|garments worn by dogs|Rug (animal covering)|coats made from dog fur|Fur clothing}}thumb|350px|Coat variation of the dog

The coat of the domestic dog refers to the hair that covers its body. Dogs demonstrate a wide range of coat colors, patterns, textures, and lengths.

As with other mammals, a dog's fur has many uses, including thermoregulation and protection from cuts or scratches; furthermore, a dog's coat plays an important role in the showing of purebred dogs. Breed standards often include a detailed description of the nature and attributes of that breed's ideal coat.

A dog's coat is composed of two layers: a top coat of stiff guard hairs that help repel water and shield from dirt, and an undercoat of soft down hairs, to serve as insulation.<ref>{{cite web|url=http://spoiled-pets.com/blogs/a-day-in-the-life-of-a-spoiled-pet|title=How to Keep Your Dog Warm This Winter|year=2014|publisher=Spoiled Pets Shop|access-date=November 10, 2014}}</ref> Dogs with both under coat and top coat are said to have a ''double coat''. Dogs with a ''single coat'' have a coat composed solely of guard hairs, with little or no downy undercoat.

The terms fur and hair are often used interchangeably when describing a dog's coat, however in general, a double coat, like that of the Newfoundland and most livestock guardian dogs, is referred to as a ''fur coat'', while a single coat, like that of the Poodle, is referred to as a ''hair coat''.

==Genetics== {{Main|Dog coat genetics}} thumb|A Labrador exhibiting a yellow coat colour

Domestic dogs exhibit diverse coat colours and patterns. In many mammals, different colour patterns are the result of the regulation of the Agouti gene, which can cause hair follicles to switch from making black or brown pigments to yellow or nearly white pigments. The most common coat pattern found in modern wolves is agouti, in which the upperside of the body has banded hairs and the underside exhibits lighter shading. The colour yellow is dominant to the colour black and is found in dogs across much of the world and the dingo in Australia.<ref name=Bannasch2021/>

In 2021, a study of whole genome sequences taken from dogs and wolves focused on the genetic relationships between them based on coat colour. The study found that most dog colour haplotypes were similar to most wolf haplotypes, however dominant yellow in dogs was closely related to white in arctic wolves from North America. This result suggests a common origin for dominant yellow in dogs and white in wolves but without recent gene flow, because this clade was found to be genetically basal to the golden jackal and genetically distinct from all other canids. The most recent common ancestor of the golden jackal and the wolf lineage dates back to 2 million years ago. The study proposes that 35,000 years ago there was genetic introgression into the Late Pleistocene grey wolf from a ghost population of an extinct canid which had diverged from the grey wolf lineage over 2 million years ago. This colour diversity could be found 35,000 years ago in wolves and 9,500 years ago in dogs. A closely related haplotype exists among those wolves of Tibet which possess yellow shading in their coats. The study explains the colour relationships between modern dogs and wolves, white wolves from North America, yellow dogs, and yellowish wolves from Tibet. The study concludes that during the Late Pleistocene, natural selection laid the genetic foundation for modern coat colour diversity in dogs and wolves.<ref name=Bannasch2021/>

During evolution of the dog from their wolf ancestors, coat colors in dogs were probably the inadvertent outcome of some other selective process, and were not likely initially selected for intentionally by humans.<ref>{{Cite book |editor = James Serpell |year = 1995 |title = The Domestic Dog: Its Evolution, Behaviour and Interactions with People |publisher = Cambridge University Press |location = Cambridge, United Kingdom |page = [https://archive.org/details/domesticdogitsev00serp/page/284 284] |isbn = 978-0-521-42537-7 |url-access = registration |url = https://archive.org/details/domesticdogitsev00serp/page/284 }}</ref> Research has found that tameness brings associated physical changes, including coat colouring and patterning.<ref>{{cite journal |author=Lyudmila N. Trut |title=Early Canid Domestication: The Farm-Fox Experiment |journal=American Scientist |volume=87 |issue=2 |pages=160–169 |date=March–April 1999 |doi=10.1511/1999.2.160 |bibcode=1999AmSci..87.....T }}</ref>

Domestic dogs often display the remnants of countershading, a common natural camouflage pattern. The basic principle of countershading is when the animal is lit from above, shadows will be cast on the ventral side of the body. These shadows could provide a predator or prey with visual cues relating to the movement of the animal. By being lighter colored on the ventral side of the body, an animal can counteract this, and thereby fool the predator or prey. An alternative explanation is that the dorsal and ventral sides of an animal experience different selection pressures (from the need to blend into different backgrounds when viewed from above and below) resulting in differing coloration.<ref>{{cite journal |author1=Graeme D. Ruxton |author2=Michael P. Speed |author3=David J. Kelly |title=What, if anything, is the adaptive function of countershading? |journal=Animal Behaviour |volume=68 |issue=3 |pages=445–451 |date=September 2004 |doi=10.1016/j.anbehav.2003.12.009 |s2cid=43106264 }}</ref>

==Nomenclature of colours and patterns==

===Colors=== The same colour may be referred to differently in different breeds. Likewise, a same term may mean different colourations in different breeds.

====Brown, chocolate, liver==== '''Brown''', '''chocolate''' and '''liver''' are the most common terms used to refer to the bb-dilution of black pigment to a dark brown. Depending on breed and exact shade, terms such as mahogany, midtone brown, grey-brown, blackish brown are used. ''Sedge'' and ''deadgrass'' are used to describe the desired Chesapeake Bay Retriever color that resembles "that of its working surroundings" as closely as possible. <gallery mode="packed" widths="250px"> File:Chesapeake Bay Retriever1.jpg|Brown Chesapeake Bay Retriever File:Hilu the Australian Kelpie dog.jpg|Red Australian Kelpie File:Chocolate Labrador Retrievers pair.jpg|Dark and light chocolate Labrador Retrievers </gallery>

====Red==== '''Red''' refers to reddish shades of orange, brown, and tan. Terms used include orange, red-gold, cinnamon, tan, and ruby. Genetically a dog called red is usually a clear sable (with little to no eumelanin tipping on hairs) or a ruddy recessive yellow.

In some breeds, "red" refers to what would usually be called brown, chocolate, or liver. A "red merle" is always a liver-based merle. In Australian Cattle Dogs, "red" stands for a densely ticked liver-based colouration with an overall red-grey appearance.

<gallery mode="packed" widths="250"> File:Seter irlandzki profil 5o899.jpg|Red Irish Setter File:01 Chow Chow.jpg|Red Chow Chow File:Owning the back step (3641313887).jpg|Red Standard Poodle File:Ariel Cavalier King Charles Spaniel.jpg|Ruby Cavalier King Charles Spaniel File:Australian Cattle Dog red.JPG|Red Australian Cattle Dog File:A Shiba Inu.jpg|Red Shiba Inu File:Basset Fauve de Bretagne portrait.jpg|Red Basset Fauve de Bretagne File:Cocker spaniel angielski zlotyy.jpg|Red Cocker Spaniel File:Vizsla-profile.jpg|Vizsla </gallery>

====Gold and yellow==== '''Gold''' refers specifically to a rich reddish-yellow and its variants, whereas '''yellow''' can refer to any shade of yellow and tan. Terms used include yellow-gold, lion-colored, fawn, apricot, wheaten, tawny, straw, yellow-red, mustard, sandy, honey, blond, and lemon. Dogs called golden or yellow tend to be recessive yellow, but can also be sable. <gallery mode="packed" widths="250"> File:Agility Poodle.jpg|Apricot Poodle File:3 Golden Retrievers in the water.jpg|Dark Golden Retrievers File:Stretched Dachshund.jpg|Yellow Dachshund File:YellowLabradorLooking.jpg|Yellow Labrador Retriever File:Golden retriever.jpg|Dark Golden Golden Retriever File:Milù 050.JPG|Orange Pomeranian (dog) File:Zazu the dog on Lion's Head mountain 24.jpg|Yellow mixed breed of unknown parentage </gallery>

====Cream==== '''Cream''' refers to a pale yellowish or tannish colour which can be almost white.

<gallery mode="packed" widths="250px"> File:Poodle, white standard 01.jpg|Pale cream Standard Poodle File:FrenchBulldog.jpg|Cream French Bulldog File:Yuki and Branca - Japanese Akita.jpg|Cream Akita </gallery>

====Fawn==== '''Fawn''' typically refers to a yellow, tan, light brown, or cream dog that has a dark melanistic mask.

With Weimaraners, ''fawn'' refers to their typical brownish grey colouration that with other breeds is usually called lilac.

<gallery mode="packed" widths="250"> File:Pug 600.jpg|Silver Fawn Pug File:Westgort Anticipation.JPG|Fawn English Mastiff File:Malinois puppy.JPG|Fawn Belgian Shepherd Malinois with breed-typical ''extended [dark] mask'' File:Male fawn Boxer undocked.jpg|Fawn Boxer File:HuntHillBoerboelsGunston1.jpeg|Fawn Boerboel </gallery>

====Black==== '''Black''' is a pure black that can get grizzled as the dog ages, or have a tendency to gain a brownish cast when exposed to the elements.

<gallery mode="packed" heights="150"> File:Newfoundland dog.jpg|Newfoundland File:Black_labrador_on_green_grass.png|Elderly black Labrador Retriever with age-related grey hairs on head and feet File:Schipperke image 001.jpg|Black Schipperke File:Crni Patuljasti šnaucer.jpg|Black Schnauzer </gallery>

====Blue==== '''Blue''' is a cool-toned, metallic grey. It typically means a ''d/d'' dilution of black pigment, a grey colouration that is grey from birth, but has a wide range of breed-specific meanings.

In Kerry Blue Terriers, Poodles, and Bearded Collies, "blue" refers to colouration that is black at birth and progressively greys out as the dog matures. In Australian Shepherds, Rough Collies, and Shetland Sheepdogs, blue means a blue (black-based) merle. In Australian Silky Terriers, blue means a saddle-type black and tan pattern, where the black parts of the coat progressively fade to a steel grey as the dog matures and in Australian Cattle Dogs, blue stands for a densely ticked black-based colouration with an overall blue-grey appearance.

<gallery mode="packed" widths="250px"> File:Standing_Neo.jpg|Blue Neapolitan Mastiff

File:PastorBelga-AlemaoDSC 2788.jpg|Blue mixed-breed dog File:Australian Silky Terrier Karlyermai Classic Touch.jpg|Blue Australian Silky Terrier File:Australian blue cattle dog 04.JPG|Blue Australian Cattle Dog </gallery>

====Grey==== '''Grey''' simply means a grey colouration of any shade. It can be used as an alternative synonym of blue, but tends to mean some other type of grey than the ''d/d'' dilution of black. Synonyms include silver, pepper, grizzle, slate, blue-black grey, black and silver, steel. Greys of a dusty or brownish cast are often lilac, a ''d/d'' dilution of liver, and this colouration does not have much of a commonly recognised name. Across various breeds, it is called lavender, silver-fawn, isabella, fawn, café au lait or silver beige.

In Poodles, a blue is a very slowly fading, very dark steel grey, whereas a silver is a quicker to clear, much lighter grey that can range from a pale platinum to a steel grey. Both are black at birth with minimal markings to indicate future change. Similarly, café au lait is a slower and darker and silver beige a quicker and lighter progressively greying brown, i.e. liver.

<gallery mode="packed" widths="250px"> File:Waterloo 027 4x6.JPG|Lighter and darker fawn Weimaraners File:Miniature Schnauzer 2.jpg|Silver Miniature Schnauzer File:Spooky (8359203146).jpg|Young Silver Standard Poodle in the earliest stages of graying out File:Doberman Fawn 001.jpg|Isabella/fawn Dobermann </gallery>

====White==== '''White''': Such a light cream that it is seen and described as pure white, making them distinct from albino dogs. A white dog, as opposed to an albino one, has dark pigment around the eye rims and nose, often coupled with dark-colored eyes. There is often some coat identifiable as cream between the dog's shoulder blades. Extreme piebald dogs can also appear all white, but are caused by a separate factor.

<gallery mode="packed" widths="250"> File:American Eskimo Dog.jpg|White American Eskimo Dog File:Bichon Frise 600.jpg|White Bichon Frisé File:Maltese at NZ National Dog Show.jpg|White Maltese dog File:Coton de Tulear puppy.jpg|White Coton de Tulear puppy File:Bruno spitz japones.jpg|White Japanese Spitz File:Samoyed Image 001.jpg|Samoyed dog File:Westhighlandterrier.jpg|West Highland White Terrier </gallery>

===Patterns=== The same pattern may be referred to differently in different breeds.

{| class=wikitable |- |align=center|100x100px Black and Tan Dachshund |align=center|110x110px Black and tan Miniature Pinscher |'''Black and tan, liver and tan, blue and tan''': Coat has both colors but in clearly defined and separated areas, usually with the darker color on most of the body and tan (reddish variants) underneath and in highlights such as the eyebrows. Black and brindle and liver and brindle, in which the same pattern is evident with brindling in place of tan, are also possible, but less common. |- |align=center| 100px Black and white Border Collie |align=center| 100px Blenheim (Red-brown and white) Cavalier King Charles Spaniel |'''Piebald''' or '''pied''' (also called '''bicolor''', '''tricolor''', '''Irish spotted''', '''Flashy''', '''Patched''', '''Tuxedo'''): any color or pattern coupled with white spotting. This can range anywhere from white toes and tail tip to a mostly white dog with color around the base of the ears and tail. Some breeds have special names for the color combinations; for example, Cavalier King Charles Spaniel uses ''Blenheim'' for reddish brown (chestnut) and white. Irish Spotted or flashy pattern is symmetrical and includes a white chest, white band around the neck, white belly, and white feet or "boots". This pattern is commonly seen in herding dogs, and Boxers, among others. The piebald gene is responsible for this pattern. |- |align=center| 100px Extreme piebald Borzoi with small colored patches |align=center| 100px Piebald white Dogo Argentino |'''Extreme piebald''' or '''piebald white''': an extensive piebald pattern that renders the dog mostly or all white with pink skin. Usually some pigmented specks remain. Governed by the piebald gene.

|- |align=center|109x109px Tricolor Basset Hound |align=center|100px Tricolor Beagle |'''Tricolor''': Three clearly defined colors, usually either black, liver, or blue on the dog's upper parts, white underneath, with a tan border between and tan highlights; for example, the Smooth Collie, the Rough Collie, the Papillon, or the Sheltie. Tricolor can also refer to a dog whose coat is patched, usually two colors (such as black and tan) on a white background. |- |align=center| 100px Blue merle tricolor Shetland Sheepdog |align=center| 100px Red merle Catahoula Leopard Dogs |'''Merle''': Marbled coat with darker patches and spots of the specified color. Merle is referred to as "Dapple" in Dachshunds. |- |align=center |100px Tuxedo Lab mix. |align=center| 85px Tuxedo Collie mix |'''Tuxedo''': Solid (often black) with a white patch (shirt front) on the chest and chin, and white on some or all of the feet (spats.) Named after the tuxedo dinner suit, the pattern is common in dogs that carry only one piebald gene (a heterozygous carrier). |- |align=center |100px Harlequin Great Dane |align=center |100px Harlequin Great Dane |'''Harlequin''': "ripped" splotches of black on white. The Great Dane is the only breed with this pattern. The term harlequin is also sometimes used to describe a piebald spotting pattern, such as parti-colored poodles. |- |align=center|100px Spotted Dalmatian |align=center |100px Spotted mutt in Sinamaica, Venezuela |'''Spotted''' Coin-sized pigmented spots on a white background. The spotting on Dalmatians is unique as it involves mutations in at least three different spotting genes.<ref name="Murphy2">{{cite book |author=Edward J. Cargill1, Thomas R. Famula, Robert D. Schnabel, George M. Strain & Keith E. Murphy |title=The color of a Dalmatian's spots: Linkage evidence to support the TYRP1 gene |journal=BMC Veterinary Research |volume=1 |issue=1 |page= 1|date=July 2005 |isbn=978-1-74661-481-2 |pmid=16045797 |pmc=1192828 |doi=10.1186/1746-6148-1-1 |doi-access=free }}</ref> |- |align=center|100px Red-speckled Australian Cattle Dog |align=center|100px Liver-ticked German Shorthaired Pointer |rowspan=2|'''Flecked, ticked, speckled''': also called '''belton''' in English Setters |- |align=center| 100px Orange belton (orange and white speckled) English Setter |align=center| 100px Blue speckled Australian Cattle Dog |- |align=center|100x100px Brown brindle and white Boxer |align=center| 100px Very sparsely brindled Great Dane |'''Brindle''': A mixture of black/liver/blue/lilac and red/yellow/cream arranged in a vertical "tiger stripe" pattern. |- |align=center| 100px Airedale Terrier with large black saddle |align=center| 100px Norwegian Dunker with merle-affected black saddle |'''Saddle''' or '''blanket''': A different color, usually darker, over the centre of the back. |- |align=center|100px Dark orange sable Pomeranian |align=center|131x131px Sable Pembroke Welsh Corgi |{{anchor|Sable (dog)}}'''Sable''': Black-tipped hairs overlaid onto a different coloured, lighter background, including grey, silver and gold.{{r|Cunliffe}} |- |center|135x135pxHairless Chinese Crested Dog |center|150px Xoloitzcuintle |'''Hairless''': Some dogs are born without a fur coat. |}

== Length and texture == [[File:Bearded Collie 600.jpg|alt=Bearded Collie showing furnishings|thumb|170x170px|frameless|170x170pxBearded Collie (top, with facial furnishings) vs border collie (bottom, no furnishings)]] {{hatnote|For more detail see: Genes associated with hair length, growth, and texture}}

Dogs demonstrate an enormous diversity in coat length and texture, from the very short and smooth coat seen in the vizslas, to the wiry coat of a Scottish Terrier and the corded coat of the Puli and the Komondor.

Generally, coats vary along three categories: length (long vs. short), texture (curly vs. straight), and coarseness (wire-haired vs. non-wire). These three categories all interact with one another; thus, one can see a short, curly, and wired coat in the Wirehaired Pointing Griffon, and a long, straight, and non-wired coat in the Pomeranian.<ref name=":0">{{Cite book|title=Coat variation in the domestic dog is governed by variants in three genes.|author=Elaine Cadieu|author2=Edouard Neff|author3=Mark Quignon|author4=Pascale Walsh|author5=Kari Chase|author6=Kevin Parker|author7=Heidi Vonholdt|author8=Bridgett Rhue|author9=Alison Boyko|author10=Adam Byers|author11=Alexandra Wong|author12=Aaron Mosher|author13=Dana Elkahloun|author14=Abdel Spady|author15=Tyrone André|author16=Catherine Lark|author17=K Gordon Cargill|author18=Michelle Bustamante|author19=Carlos Wayne|author20=Robert Ostrander|oclc=799147453}}</ref>

Additionally, breeds show variation in patterns of growth - that is to say, parts of the dog's body where the coat may be longer or shorter. The same gene that controls wiriness of hair also causes furnishings to be present (e.g. beard, moustache, eyebrows) <ref name=":0" /> - compare the bearded collie, furnishings present, to the border collie, which lacks furnishings. Some breeds show feathering: fringes of longer hair on the ears, belly, tail, and back of the legs (e.g., Saluki and any of the setters).

Dogs also vary in the thickness of the undercoat. Some dogs have only a single (rather than a double) coat, or a very reduced undercoat (e.g. the Vizsla), which results in a thinner coat. Certain breeds, especially spitz-type breeds, tend to have a thicker undercoat, which helps retain heat in cold and wet weather.

Furthermore, complete hairlessness on parts of the body is present in breeds such as the Chinese Crested or the Xoloitzcuintli.

== Shedding == {{anchor|blowing the coat}} thumb|left|A slicker brush with wire bristles, used for removing loose hair from the coat Shedding of hair can occur continuously, but in many breeds is strongly influenced by hormones. Seasonal shedders shed most in spring and fall, following an increase or decrease in day length, and least in summer and winter, in response to constant day length. Cold temperatures stimulate hair growth, so that the heaviest shedding is in spring on dogs living in cold climates. Artificial lighting can alter the seasonal shedding pattern of dogs who live indoors. Other hormonal influences include dietary factors, reproductive hormones in intact dogs, and various medical conditions and disorders. Shedding that is done in a short period of time is known as "blowing the coat" or "blowing coat".<ref name="Blackburn">{{cite book|url=https://books.google.com/books?id=r_LsDQAAQBAJ&q=blowing+coat&pg=PT110|title=The Everything Dog Grooming Book: All you need to help your pet look and feel great!|last=Blackburn|first=Sandy|date=2008|publisher=Simon & Schuster|isbn=978-1-4405-1214-8|location=Avon, Massachusetts|page=110|access-date=2017-07-04}}</ref><ref>{{cite book|url=https://books.google.com/books?id=j8EJBgAAQBAJ&q=blow+coat&pg=PT36|title=Pug|author=Dog Fancy|date=2011|publisher=Lumina Media|isbn=978-1-59378-839-1|location=New York|page=36|author-link=Dog Fancy|access-date=2017-07-04}}</ref> Among the other coat types, dogs with fine silky coats (e.g., spaniels) are generally moderate shedders, those with an intermediate coat texture (e.g., mountain dogs) are generally heavy shedders, and those with thick stand-offish coats (e.g., spitzes) are generally very heavy shedders.

[[File:Cão de agua Português 1.jpg|thumb|The Portuguese Water Dog is an example of a breed with single, low-shedding coat.]]

"Non-shedding" dogs have greatly-reduced shedding due to alterations to the hair follicle growth cycle:

* homozygosity for the furnishings (wire) allele - Most breeds with facial furnishings (including ones whose faces are usually shaved removing the furnishings) are low-shedding, but they must be homozygous, so dogs of mixed wire/non-wire parentage (e.g., terrier crosses or breeds with wire and non-wire varieties) can be heavy shedders. There are a few furnished breeds that shed more (e.g., Old English Sheepdog, Bearded Collie, Briard, Otterhound); * at least one copy of the single-coat (non-shedding) allele - Most dogs with a smooth coat are low shedding, as well as the fringed or flat coat. There are breeds with a very short coat that shed more (e.g., Basset Hound, English Bulldog, Pug, Toy Fox Terrier, Dalmatian, Vizsla, German Shorthaired Pointer); * single coat (no undercoat) plus furnishings (homozygous) - These breeds shed the least (e.g., Poodle, Soft-coated Wheaten Terrier).

===Hypoallergenic coat=== {{main|Hypoallergenic dog breed}} "[D]ogs are a relevant source of allergens, but diagnosing dog-related allergies may present difficulties ..."<ref name="ARHeutelbeck(2008)">{{cite journal|vauthors=Heutelbeck AR, Schulz T, Bergmann K, Hallier E|date=Jan 2008|title=Environmental Exposure to Allergens of Different Dog Breeds and Relevance in Allergological Diagnostics|journal=Journal of Toxicology and Environmental Health, Part A|volume=71|issue=11–12|pages=751–8|doi=10.1080/15287390801985513|pmid=18569573|bibcode=2008JTEHA..71..751H |s2cid=37091773}}</ref> Some dog breeds have been promoted as hypoallergenic (which means ''less allergic'', not free of allergens) because they shed very little. However, no canine is known to be completely nonallergenic. Often the problem is with the dog's saliva or dander, not the fur.<ref>{{cite news|url=https://www.nytimes.com/1997/02/05/us/nonallergenic-dog-not-really.html?n=Top%2FNews%2FScience%2FTopics%2FAnimals|title=Nonallergenic Dog? Not Really|last=Grady|first=Denise|date=February 5, 1997|newspaper=New York Times|access-date=April 3, 2011}}</ref> Although breeds such as poodles, Bedlington terriers, bichons, yorkies, and wire-haired terriers are commonly represented as being hypoallergenic due to reduced shedding, the reaction that an individual person has to an individual dog may vary greatly. In a report, describing dog allergen extracts of dog hair, belonging to patients' dogs or from dogs of the same breed, with low molecular mass that are absent in extracts of commercial allergen test kits, it has been found that "[f]actors related to individual dogs seem to influence the allergenicity more than breed or gender."<ref name="ARHeutelbeck(2008)" />

==Show coats== The nature and quality of a purebred dog's coat is important to the dog fancy in the judging of the dog at conformation shows. The exact requirements are detailed in each breed's breed standard and do not generalise in any way, and the terminology may be very different even when referring to similar features. See individual breed articles for specific information.

== Nutritional impacts on coat == A dog's coat is an outward indicator of internal well-being.<ref name=":42">{{Cite journal|last1=Kirby|first1=Naomi A.|last2=Hester|first2=Shaleah L.|last3=Bauer|first3=John E.|title=Dietary fats and the skin and coat of dogs|journal=Journal of the American Veterinary Medical Association|language=en|volume=230|issue=11|pages=1641–1644|doi=10.2460/javma.230.11.1641|pmid=17542730|year=2007|doi-access=free}}</ref> For this reason, coat health is an important aspect of pet care to many dog owners.<ref name=":42"/> Dog coats can be impacted by nutritional components from the diet.<ref name=":52">{{Cite journal|last=Watson|first=Tim D. G.|date=1998-12-01|title=Diet and Skin Disease in Dogs and Cats|journal=The Journal of Nutrition|language=en|volume=128|issue=12|pages=2783S–2789S|issn=0022-3166|pmid=9868266|doi=10.1093/jn/128.12.2783S|doi-access=free}}</ref> Below is a table that summarizes the effects of several nutrients (minerals, vitamins) on the domestic canine coat, based on current evidence: {| class="wikitable" ! Nutrient ! Role ! Impacts when deficient ! Benefits |- | Zinc | Gives strength to collagen<ref name=":72">{{Cite journal|last1=Goldberg|first1=L.|last2=Lenzy|first2=Y.|date=2010|title=Nutrition and hair|url=http://www.cidjournal.com/article/S0738-081X(10)00062-3/references|journal=Clinics in Dermatology|volume=28|issue=4|pages=412–419|doi=10.1016/j.clindermatol.2010.03.038|pmid=20620758|url-access=subscription}}</ref> | Dry and brittle coat<ref name=":72"/> | Contributes to coat growth and prevents brittle and dry coat<ref name=":72"/> |- | Copper | Involved in keratinization<ref name=":02">{{Cite journal|last=Tewari, Singh, Gautam, Dwivedi|date=December 2013|title=Nutritional dermatosis - a review|url=http://go.galegroup.com.subzero.lib.uoguelph.ca/ps/i.do?&id=GALE|A375288515&v=2.1&u=guel77241&it=r&p=AONE&sw=w&authCount=1|journal=Intas Polivet|volume=14|pages=199–202|via=GALE}}</ref> | Brittle fur, hypo-pigmentation, discoloration<ref name=":02"/> | Improved color and keratinization<ref name=":02"/> |- | Selenium | Cell growth; antioxidant<ref name=":92">{{Cite journal|last1=Guo|first1=E.|last2=Katta|first2=R.|date=2017|title=Diet and hair loss: effects of nutrient deficiency and supplement use|journal=Dermatol Pract Concept|volume=7|issue=1|pages=1–10|doi=10.5826/dpc.0701a01|pmc=5315033|pmid=28243487}}</ref><ref name=":1">{{Cite journal|last1=Kapun|first1=A. Plevnik|last2=Salobir|first2=J.|last3=Levart|first3=A.|last4=Kalcher|first4=G. Tavčar|last5=Svete|first5=A. Nemec|last6=Kotnik|first6=T.|date=2014-12-06|title=Vitamin E supplementation in canine atopic dermatitis: improvement of clinical signs and effects on oxidative stress markers|url=http://veterinaryrecord.bmj.com/content/175/22/560|journal=Veterinary Record|language=en|volume=175|issue=22|page=560|doi=10.1136/vr.102547|issn=0042-4900|pmid=25205675|s2cid=23201891|url-access=subscription}}</ref> | Sparse coat growth<ref name=":92"/> | Coat growth promotion<ref name=":1" /> |- | Vitamin{{nbsp}}A | Proliferation of keratinocytes<ref name=":22">{{Cite journal|last=Baviskar, Jayanthy & Nagarajan|date=2013|title=Vitamin - a responsive dermatosis in a dog|journal=Intas Polivet|volume=14|page=210}}</ref> | Rough coat<ref name=":22"/> | Proliferation of keratinocytes; hair follicle growth<ref name=":32">{{Cite journal|last1=Kurtenbach|first1=Stefan|last2=Mayer|first2=Christoph|last3=Pelz|first3=Thomas|last4=Hatt|first4=Hanns|last5=Leese|first5=Florian|last6=Neuhaus|first6=Eva M.|date=2011-08-09|title=Molecular evolution of a chordate specific family of G protein-coupled receptors|journal=BMC Evolutionary Biology|volume=11|issue=1 |page=234|doi=10.1186/1471-2148-11-234|pmid=21827690|pmc=3238225|issn=1471-2148 |doi-access=free |bibcode=2011BMCEE..11..234K }}</ref><ref name=":22"/> |- | Biotin | Saturation of Coat<ref name=":172">{{Cite journal|jstor=30158351|title=The Effects of Biotin Deficiency on Hair Development and Pigmentation|journal=Physiological Zoology|volume=25|issue=2|pages=145–149|last1=Rauch|first1=Harold|year=1952|doi=10.1086/physzool.25.2.30158351|s2cid=87665589}}</ref> | Alopecia and achromotrichia beginning at the root of the coat<ref name=":172"/> | Contributes to coat shine, thickness/distribution of hair follicles<ref name=":172"/> |}

=== Trace minerals ===

==== Zinc ==== {{Main|Zinc}} Zinc contributes to hair growth and can prevent hair from becoming dry and brittle.<ref name=":72" /> In addition to, zinc when supplemented in combination with linoleic acids has been found to improve the coat of canines by reducing water loss in the trans-epidermal layer of the skin.<ref name=":112">{{Cite journal|last1=Marsh|first1=K.|last2=Coe|first2=S.|last3=Ruedisueli|first3=F.|last4=Watson|first4=T.|date=2000|title=Effects of zinc and linoleic acid supplementation on the skin and coat quality of dogs receiving a complete and balanced diet|journal=Veterinary Dermatology|volume=11|issue=4|pages=277–284|doi=10.1046/j.1365-3164.2000.00202.x}}</ref> Dogs can obtain zinc in their diet, through the addition of various ingredients, including; red meats, whole grains, poultry by-product meals, and fish meals.

==== Copper ==== {{Main|Copper}} Copper is a trace mineral that is required in the diet of canines at 7.3 mg/kg.<ref name=":152">{{Cite web|url=http://www.aafco.org/publications|title=The Association of American Feed Control Officials > Publications|website=www.aafco.org|language=en-US|access-date=2017-11-28}}</ref> Copper is involved in multiple enzymatic pathways. In dogs, a lack of copper in the diet, leading to a copper deficiency, results in incomplete keratinization.<ref name=":02" /> This leads to a dry coat, hypo-pigmentation, and discoloration of the coat.<ref name=":02" />

==== Selenium ==== {{Main|Selenium in biology}} Selenium is another one of the many trace minerals essential for a dog's diet. Selenium is typically required in lower levels in comparison to other minerals. It is involved in the prevention of oxidative damage as well as the production of anti-oxidants.<ref name=":92" /> Selenium aids in the promotion of coat growth.<ref>{{Cite journal|last1=Hatfield|first1=D.|last2=Tsuji|first2=P.|last3=Carlson|first3=B.|last4=Gladyshev|first4=V.|date=2014|title=Selenium and selenocysteine: roles in cancer, health and development|journal=Trends Biochem Sci|volume=39|issue=3|pages=112–120|doi=10.1016/j.tibs.2013.12.007|pmc=3943681|pmid=24485058}}</ref> Lack of selenium in the diet of a dog can contribute to the occurrence of sparse coat growth.<ref name=":10">{{Cite journal|last1=Sengupta|first1=A.|last2=Lichti|first2=U.|last3=Carlson|first3=B.|last4=Ryscavage|first4=A.|last5=Gladyshev|first5=V.|last6=Yuspa|first6=S.|last7=Hatfield|first7=D.|date=2010|title=Selenoproteins are essential for proper keratinocyte function and skin development|journal=PLOS ONE|volume=5|issue=8|article-number=e12249|doi=10.1371/journal.pone.0012249|pmc=2923614|pmid=20805887|bibcode=2010PLoSO...512249S|doi-access=free}}</ref> Dogs can obtain selenium in their diet through the addition of various ingredients including; tuna fish, halibut, sardines, beef, chicken, and egg.

=== Vitamins === {{Main|Vitamin}}

==== Vitamin A ==== {{Main|Vitamin A}} Vitamin A deficiency can lead to rough coat, scaling of skin, and other dermatitis issues like alopecia.<ref name=":22" /> It is also essential for cells to properly proliferate keratinocytes,<ref name=":22" /> which are epithelial cells that produce keratin on the outermost layer of the skin for the cortisol cells of the hair follicle.<ref name=":32" /> A deficiency in vitamin A can cause the common symptoms of dermatitis (dry, scaling skin and dull coat).<ref name=":6">{{Cite journal|last1=Beigh|first1=S.A|last2=Soodan|first2=J.S|last3=Bhat|first3=A.M|last4=Singh|first4=V|last5=Tantary|first5=H|date=2013|title=Clinical diagnosis and management of vitamin--a responsive canine dermatosis|journal=Intas Polivet|volume=14|issue=2|pages=207–210}}</ref>

==== Vitamin B7 (Biotin) ==== {{Main|Biotin}} Vitamin B7, also known as biotin, is a water-soluble nutrient that is known to play a role associated with the maintenance and development of hair starting from the follicle. Although it has not been clinically shown to improve hair growth with supplementation alone, it has been shown to reverse deficiency in dogs born deficient.<ref>{{Cite journal|last1=Zempleni|first1=Janos|last2=Hassan|first2=Yousef I|last3=Wijeratne|first3=Subhashinee SK|date=2008-11-01|title=Biotin and biotinidase deficiency|journal=Expert Review of Endocrinology & Metabolism|volume=3|issue=6|pages=715–724|doi=10.1586/17446651.3.6.715|issn=1744-6651|pmc=2726758|pmid=19727438}}</ref>

Symptoms of biotin deficiency include alopecia and achromotrichia. A clinical study of biotin showed the importance of biotin in coat pigmentation. There different stages of hair development, as shown in clinical studies using mice.<ref name=":172"/> Each stage of hair development has a different sensitivity to biotin present in the body. For example, the shaft development is not greatly affected by biotin access.<ref name=":172" /> During the last stage, the amount of biotin available for use by the body will alter the success of that development greatly.<ref name=":172" /> Throughout the hair development, most stages of growth are completed, but it was found that in the last stage, where biotin levels were insufficient, there was an incorrect keratinization of the root of the hair, causing the hair to fall out of the body.<ref name=":172" />

The supplementation of biotin cannot reverse affects caused by deficiency, but as soon as supplementation is given and biotin levels are restored to adequacy, the body begins to produce the usual hair growth and color it would before the deficiency took place.<ref name=":172" />

=== Essential fatty acids === Polyunsaturated fatty acids found in the diet play a critical role in the maintenance of a healthy coat in dogs, and have even been shown to improve coat condition when supplemented in the diet.<ref name=":52"/> Furthermore, diets lacking essential fatty acids in their diet will manifest as unkept, matted coat.<ref name=":42"/> Omega fatty acids 3 and 6 are highly unsaturated fatty acids, making them especially metabolically active.<ref name=":12">{{Cite journal|last1=Murru|first1=Elisabetta|last2=Banni|first2=Sebastiano|last3=Carta|first3=Gianfranca|date=2013|title=Nutritional Properties of Dietary Omega-3-Enriched Phospholipids|journal=BioMed Research International|language=en|volume=2013|article-number=965417|doi=10.1155/2013/965417|pmid=23984423|pmc=3747496|issn=2314-6133|doi-access=free}}</ref>

The proper combination of these omega fatty acids is crucial to achieve optimal benefits. Proper omega 6:3 ratios have been shown to diminish allergy triggered immune responses, thus improving overall coat condition.<ref name=":13">{{Cite book|title=Canine and feline nutrition: a resource for companion animal professionals|date=2011|publisher=Mosby|others=Case, Linda P.|isbn=978-0-323-06619-8|edition=3rd|location=Maryland Heights, Mo.|oclc=664112342}}</ref> The National Research Council (NRC) recommends a 2.6:1 to 26:1 omega 6:3 ratio for adult dog maintenance diets.<ref>{{Cite book|title=Nutrient requirements of dogs and cats|last=Nutrition.|first=National Research Council (U.S.). Ad Hoc Committee on Dog and Cat|date=2006|publisher=National Academies Press|isbn=978-0-309-08628-8|edition=[Rev. ed.]|location=Washington, D.C.|oclc=62741464}}</ref> The proper ratio of these fatty acids is crucial because each has an opposing role in inflammation within the body and both compete for the same enzymatic pathway.<ref name=":42" /> Dogs, like many mammals, lack the desaturase enzymes capable of interconverting omega 3 and 6 fatty acids.<ref name=":12" /> Therefore, the amount of inflammation in the body is dependent on the ratio between omega 3 and 6 fatty acids. Too little inflammation suppresses the immune system and the body's ability to heal, however excessive inflammation can irritate the skin and reduce the coat's overall appearance.<ref name=":42" />

Aside from omega fatty acids, lipid content in the canine diet is an important aspect of coat health.<ref name=":42" /> The fat soluble vitamins (A, D, E and K) require lipids present in the diet for absorption, transport and deposition in canine adipose tissue.<ref name=":14">{{Cite journal|last1=Debier|first1=C.|last2=Larondelle|first2=Y.|date=February 2005|title=Vitamins A and E: metabolism, roles and transfer to offspring|journal=The British Journal of Nutrition|volume=93|issue=2|pages=153–174|issn=0007-1145|pmid=15788108|doi=10.1079/bjn20041308|doi-access=free}}</ref> The specific role of vitamins A and E for coat health are explored elsewhere in this article, as they pertain to immune function.<ref name=":14" /> Another pet food regulating body, the Association of American Feed Control Officials (AAFCO), recommends that Vitamin E supplementation increase as polyunsaturated fatty acids are added to diet in order to counteract lipid oxidation and maintain the potency.<ref name=":152"/> In addition, high fat diets in dogs were shown to dramatically improve coat sheen and appearance.<ref name=":42" /> It is thought excess cholesterol esters are incorporated into the hair follicle, leading to the improved coat appearance.<ref name=":42" /> The same study, by Kirby, Hester and Bauer (2007), stated the optimal approach to an improved coat in dogs is a combination of increased dietary fat and the proper amount of polyunsaturated fatty acids.<ref name=":42" />

==== Omega 3 (linolenic acid) ==== {{Main|Omega-3 fatty acid}} Omega 3 fatty acid, also known as linolenic acid, is an anti-inflammatory compound.<ref name=":13" /> Linolenic acid is found in the oil from flaxseeds, soybean and canola.<ref name=":13" /> Some better known examples of linolenic acid are the metabolic derivatives eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA). EPA inhibits the enzyme delta-5-desaturase, which prevents the synthesis of arachidonic acid which is an inflammatory omega 6.<ref name=":16">{{Cite journal|last1=Lee|first1=Je Min|last2=Lee|first2=Hyungjae|last3=Kang|first3=SeokBeom|last4=Park|first4=Woo Jung|date=2016-01-04|title=Fatty Acid Desaturases, Polyunsaturated Fatty Acid Regulation, and Biotechnological Advances|journal=Nutrients|language=en|volume=8|issue=1|page=23|doi=10.3390/nu8010023|pmid=26742061|pmc=4728637|doi-access=free}}</ref> DHA acts even earlier in omega 6 metabolism, by inhibiting delta-6-desaturase.<ref name=":16" /> The anti-inflammatory properties of omega 3s stem from their ability to inhibit the inflammatory action of omega 6 fatty acids. A functional minimum has not been set forth by AAFCO, as one has yet to be determined.<ref name=":152" /> A reduction in inflammation of somatic tissues, skin especially, supports coat health.<ref name=":42" />

==== Omega 6 (linoleic acid) ==== {{Main|Omega-6 fatty acid}} Omega 6 fatty acid, also known as linoleic acid, is found in poultry fat and the oil from safflower, sunflower, corn and flaxseed.<ref name=":13" /> Arachidonic acid is a well known metabolic derivative of linoleic acid, found only in animal sources.<ref name=":13" /> As mentioned above, arachidonic acid is a pro-inflammatory compound.<ref name=":16" /> It is critical to note once again that canines are unable to interconvert between omega fatty acids and over supplying linoleic acid promotes excessive inflammation in the body, which can potentially reverse the coat benefits seen by supplying omega fatty acids in the diet. In contrast, linoleic acid is also required for epidermal lipid function and water retention, which benefits coat shine.<ref name=":112" /><ref name=":13" /> Having linoleic acid present in the diet has demonstrated a positive effect on skin, and thus by extension, coat.<ref name=":42" />

==References== {{Reflist|refs=

<ref name=Bannasch2021>{{cite journal|doi=10.1038/s41559-021-01524-x|title=Dog colour patterns explained by modular promoters of ancient canid origin|year=2021|last1=Bannasch|first1=Danika L.|last2=Kaelin|first2=Christopher B.|last3=Letko|first3=Anna|last4=Loechel|first4=Robert|last5=Hug|first5=Petra|last6=Jagannathan|first6=Vidhya|last7=Henkel|first7=Jan|last8=Roosje|first8=Petra|last9=Hytönen|first9=Marjo K.|last10=Lohi|first10=Hannes|last11=Arumilli|first11=Meharji|last12=Lohi|first12=Hannes|last13=Kere|first13=Juha|last14=Daub|first14=Carsten|last15=Hytönen|first15=Marjo|last16=Araujo|first16=César L.|last17=Quintero|first17=Ileana B.|last18=Kyöstilä|first18=Kaisa|last19=Kaukonen|first19=Maria|last20=Arumilli|first20=Meharji|last21=Salonen|first21=Milla|last22=Sarviaho|first22=Riika|last23=Niskanen|first23=Julia|last24=Hundi|first24=Sruthi|last25=Puurunen|first25=Jenni|last26=Sulkama|first26=Sini|last27=Karjalainen|first27=Sini|last28=Sukura|first28=Antti|last29=Syrjä|first29=Pernilla|last30=Airas|first30=Niina|journal=Nature Ecology & Evolution|volume=5 |issue=10 |pages=1415–1423 |pmid=34385618|pmc=8484016 |bibcode=2021NatEE...5.1415B |display-authors=1}}</ref>

<ref name=Cunliffe>{{cite book|title=The Encyclopedia of Dog Breeds|last=Cunliffe|first=Juliette|year=2004|publisher=Paragon Publishing|chapter=Coat Types, Colors and Markings|pages=20–23 and various|isbn=978-0-7525-8276-4}}</ref> }}

==Further reading== * {{cite book |title=The New Encyclopedia of the Dog |last=Fogle |first=Bruce |year=2000 |publisher=Dorling Kindersley |chapter=The Breed Section Explained |page=83 and various |isbn=978-0-7513-0471-8}}

==External links== * {{cite web | last = Schmutz | first = Sheila M. | title = Dog Coat Color Genetics | publisher = University of Saskatchewan | date = March 4, 2010 | url = http://homepage.usask.ca/~schmutz/dogcolors.html | access-date = September 12, 2010}}

Category:Animal coat colors Category:Animal hair Category:Dog anatomy