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Horse Coat Colours Presentation 2008

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<strong>Horse</strong> <strong>Coat</strong> <strong>Colours</strong> and<br />

Markings<br />

Cindy Harper<br />

Onderstepoort Laboratory for Applied<br />

Veterinary Genetics


Basic <strong>Colours</strong><br />

Black<br />

Bay<br />

Chestnut


Genetic Control of the Basic <strong>Colours</strong><br />

• Melanocytes produce melanin pigment<br />

• 2 Pigments responsible for coat and skin<br />

colour – eumelanin (black and brown) and<br />

phaeomelanin (red and yellow)<br />

• Colour genes control either the pigment<br />

producing cell or pigment production<br />

• 2 genes control the main colour switches<br />

in horses<br />

Extension (E) and Agouti (A)


Genetics<br />

Sire<br />

Dam<br />

Locus (address of a gene and each has a<br />

name) occurs on a pair of chromosomes – 1<br />

from sire and 1 from dam<br />

Form of gene (allele) on 1 chromosome of pair<br />

can be same as on other – homozygosity<br />

Or different – heterozygosity<br />

Different – dominant and recessive where 1<br />

allele is expressed and other is not<br />

Function: Gene that codes for protein<br />

Protein: Effect e.g. stimulates melanocyte to<br />

produce eumelanin<br />

Chromosome pair<br />

Result: Black horse


The Extension Gene/Locus (E)<br />

• Difference between black and red lies in the action of 1<br />

gene – MC1R<br />

• Allele symbols are E and e<br />

E extends black (eumelanin(<br />

eumelanin) ) in coat<br />

e extends red (phaeomelanin(<br />

phaeomelanin) ) in coat<br />

Combination of alleles at the extension locus:<br />

EE<br />

Ee<br />

ee<br />

Allows black in the coat: Black, brown, bay,<br />

buckskin, grullo<br />

Black in the skin but not in the coat: Chestnut,<br />

palomino


Black Pattern<br />

The Agouti Gene / Locus (A)<br />

AA<br />

Aa<br />

Black pattern limited to the legs , mane and tail<br />

aa<br />

Black distributed uniformly through the coat<br />

The combination of alleles at the extension and agouti<br />

genes / loci control the basic colour of the horse


Interaction between Extension and<br />

Agouti<br />

EEAA<br />

EEAa<br />

EeAA<br />

EeAa<br />

Black in coat<br />

Black at the points<br />

Bay, Brown<br />

EEaa<br />

Eeaa<br />

eeAa<br />

eeAA<br />

eeaa<br />

Black in coat<br />

Black throughout coat<br />

Only red in the coat coat<br />

Black,<br />

Chestnut,


Red Factor (e)<br />

• Extension locus – 2 alleles E and e<br />

ee breeding principles<br />

Chestnut + chestnut = all<br />

chestnut<br />

e<br />

e<br />

e<br />

ee<br />

ee<br />

e<br />

ee<br />

ee


Red Factor (Ee(<br />

Ee)<br />

and Black Pattern factor (Aa(<br />

Aa)<br />

Sire: eeAa<br />

chestnut<br />

eA ea<br />

chestnut + chestnut = All<br />

chestnut<br />

Extension (red) locus<br />

dominant over the Agouti<br />

(black) locus<br />

Dam: eeaa<br />

chestnut<br />

ea<br />

ea<br />

eeAa<br />

eeAa<br />

eeaa<br />

eeaa


Red Factor (Ee(<br />

Ee)<br />

and Black Pattern factor (Aa(<br />

Aa)<br />

Sire: EEaa<br />

black<br />

Ea<br />

Ea<br />

Dam: eeAA<br />

chestnut<br />

eA<br />

eA<br />

EeAa<br />

Bay<br />

EeAa<br />

Bay<br />

EeAa<br />

Bay<br />

EeAa<br />

Bay


Red Factor (Ee(<br />

Ee)<br />

and Black Pattern factor (Aa(<br />

Aa)<br />

Sire: Eeaa<br />

black<br />

Ea<br />

ea<br />

Dam: Eeaa<br />

black<br />

Ea<br />

ea<br />

EEaa<br />

Black<br />

Eeaa<br />

Black<br />

Eeaa<br />

Black<br />

eeaa<br />

Chestnut


Breeding Black<br />

• Avoid recessive e!<br />

Genetic test for E/e<br />

Is this a true black (aa(<br />

aa) ) or dark bay / brown<br />

(Aa)?<br />

Genetic test for A/a


Principle<br />

Each horse has all the genes that can possibly code for any colour, BUT an<br />

individual allele combination that in total gives it a specific appearance!<br />

Extension Locus<br />

E e<br />

Agouti Locus<br />

A A<br />

Cream Locus<br />

CR N<br />

Grey Locus<br />

g g<br />

Tobiano Locus<br />

TO N<br />

1<br />

2<br />

3<br />

4<br />

5<br />

Genotype: E/e A/A N/CR g/g N/TO<br />

Phenotype: Diluted Bay (Buckskin) Nongrey<br />

with a Tobiano Paint pattern


What colour?


Basic Colour Modification<br />

Sooty / Shaded<br />

Black hairs between coat hairs<br />

Bay – topline to extensive covering most of<br />

the body


Basic Colour Modification<br />

Sooty / Shaded<br />

Bay – extensive shading<br />

“Brown”<br />

How to distinguish from true black?<br />

Genetic test aa – black / Aa or AA - brown


The Brown Gene<br />

• There is a brown gene – (TYRP1) dilutes<br />

black to chocolate<br />

• Most obvious in dogs, but not common<br />

colour in horses and chocolate and dun<br />

horses are caused by other genes


When is a horse Brown?!<br />

• Brown in horses is a term used to<br />

describe a shade of bay in horses.<br />

• Some breeders describe all bays with<br />

shading / sootiness as Brown<br />

• Some breeders describe all bays<br />

regardless of shading as bays<br />

• Most commonly breeders describe the<br />

dark, extensively shaded bay as<br />

brown and all other bays as bay<br />

• Heritability?


Brown Heritability<br />

• Some believe that brown can be bred and is in fact a<br />

sub-division of the agouti locus or extension locus (A t or<br />

E B )<br />

• Black is allowed in the coat and is more extensive than<br />

the points in a bay<br />

• This would support the proposal that brown (“extensive(<br />

bay”) ) is heritable and “breedable”


Colour terms<br />

• Terms that describe a phenotype – what<br />

you see<br />

• Depend on breed / society / country /<br />

individual<br />

• Only right or wrong is to find and test the<br />

actual genetic control!<br />

• FEI rulebook states that the definition of<br />

colour differs according to country.


Basic Colour Modification<br />

Sooty / Shaded<br />

Chestnut – usually distributed throughout<br />

the coat<br />

Liver Chestnut


Basic Colour Modification<br />

Mealy<br />

• Mealy causes lighter areas on<br />

the belly, muzzle, inner legs,<br />

and over the eyes. It is<br />

usually ignored in color<br />

description.<br />

• Black - Seal brown (test aa is<br />

modified black / Aa or AA is<br />

bay with lots of shading)<br />

• Chestnut to sorrel for<br />

breeders of draft horses


Mealy<br />

Dun<br />

Bay


Bay<br />

• Black Points<br />

• Legs<br />

• Ear tips<br />

• Mane<br />

• Tail


Variations of Bay


Black<br />

• No Brown in coat<br />

• White markings are<br />

allowed<br />

•Genetic test aa vs Aa<br />

or AA and EE or Ee


Feature of Bay vs Black<br />

• A black horse, even with a sun-bleached<br />

hair coat will have solid black hairs around<br />

the eye.<br />

Bay<br />

Black


Chestnut<br />

e<br />

e<br />

e<br />

ee<br />

ee<br />

e<br />

ee<br />

ee<br />

Recessive traits are expressed<br />

phenotypically when in homozygous form!<br />

Red coat throughout – no black points.


Chestnut Modifications<br />

Liver<br />

Flaxen<br />

Flaxen and<br />

mealy


White on basic coat<br />

• Any white or white pattern is<br />

SUPERIMPOSED on a basic colour<br />

• Cover the whole or part of the horse<br />

• Pattern – name<br />

Grey<br />

Roan<br />

Roaning<br />

Spotting<br />

Paints<br />

White markings


Grey<br />

• Born any colour – becomes grey<br />

• Usually starts on head and is progressive<br />

• Speed of greying individual<br />

• Gradual process –<br />

completely white with pigmented<br />

skin


Grey Breeding<br />

• Dominant trait GG and Gg<br />

– always grey i.e. a horse<br />

does not carry a hidden<br />

grey gene<br />

• A grey foal must have at<br />

least 1 grey parent!<br />

• Homozygous grey + non<br />

grey 100% Grey<br />

g<br />

G<br />

Gg<br />

G<br />

Gg<br />

g<br />

Gg<br />

Gg


Grey Breeding<br />

• A horse can have any combination of base coat<br />

genes, but G overrides all<br />

e/e a/a N/RN to/to C/C G/g = GREY<br />

• Grey is going to obliterate any other colour pattern<br />

• 2 greys can<br />

• produce<br />

a non-grey<br />

• DNA Test<br />

available<br />

G<br />

G<br />

GG<br />

g<br />

Gg<br />

g<br />

Gg<br />

gg


Grey Variations<br />

• Variations of grey can given different<br />

names:<br />

Rose grey<br />

Steel grey<br />

Fleabitten grey<br />

Dapple grey


Roan<br />

• Permanent colour, , white does not progress<br />

with age!<br />

• Dark head and limbs<br />

• Characteristic inverted “V” above knees


Roan Genetics<br />

• RN is caused by a dominant gene.<br />

RNrn or rnrn (not roan) – no test yet<br />

• THUS: A roan must have 1 roan parent!<br />

• Homozygous dominant roan RNRN = lethal<br />

resorption?


Roan Variations<br />

Chestnut Roan<br />

Blue Roan


Rabicano / Roaning<br />

• Rabicano, , also called white ticking or<br />

roaning, , is characterized by limited roaning<br />

in a specific pattern, usually in the flank, sides<br />

and the tailhead<br />

• Also in breeds which do not possess any true<br />

roan Thoroughbreds and Arabians


Spots<br />

• THE LEOPARD COMPLEX<br />

• Produced by a the leopard gene complex (Lp(<br />

Lp)<br />

• It is a dominant trait – patterns produced by<br />

modifier genes<br />

• Not all horses with the dominant leopard allele<br />

(Lp)) will be spotted but indicators of this gene<br />

include:<br />

• White sclera<br />

• Mottled skin<br />

• Striped hooves


Leopard Breeding<br />

• Occurs in many breeds but in some it is a<br />

fixed characteristic<br />

Appaloosa, Knapstrup, Noriker<br />

• Dominant Lp allele expresses a pattern<br />

• Pattern depends on modifiers<br />

• <strong>Horse</strong> with a specific pattern can produce<br />

the whole range of patterns depending on<br />

the modifiers in its gene complex<br />

• No specific test


Leopard Patterns<br />

• Leopard


Blanket


Varnish Roan<br />

• Not Rn or G<br />

• Lp spotting complex gene with<br />

characteristics and may have leopard spots<br />

• Mottled skin, color mainly on bony points<br />

(on the face, usually in a distinct V on the<br />

bridge of the nose; on the cheeks, point of<br />

shoulder, elbows, knees, point of hips, hock)<br />

and it can be seasonal as well<br />

• Roans (RN) are roan from birth, varnish<br />

roans are born quite solid with some spots<br />

and "roan out" as they age


Varnish Roan Variations


Leopard Variations<br />

Small Blanket<br />

Extensive Solid Blankets<br />

Extensive Spotted Blanket or Near Leopard<br />

Leopards with various sized spots


Paints<br />

• Basic colour with a white pattern<br />

superimposed<br />

• Patterns are controlled by separate genes and<br />

are heritable<br />

• Extent of pattern can vary


Tobiano<br />

• Most legs white<br />

• White crosses the topline<br />

• General head markings (may<br />

have no head markings)<br />

• Mixed tail<br />

• Regular Edges<br />

• Dominant gene TO/TO or<br />

N/TO<br />

• Direct Genetic Test available


Tobiano Variations


Frame Overo<br />

• Dark legs<br />

• White patches on the<br />

sides<br />

• Irregular Edges<br />

• Extensive head<br />

markings<br />

• Tail one colour


Frame Overo


OLWS<br />

• Frame Overo is associated with<br />

Lethal White Foal Syndrome<br />

(LWF)<br />

• Mutation in gene supposedly<br />

produces frame overo – O/O<br />

• Test for this mutation<br />

• Some solids carry the O mutation<br />

(N/O)<br />

• N/O x N/N – always to avoid<br />

lethal<br />

• O/O solid white foal with<br />

incomplete intestinal<br />

development


Sabino<br />

• Legs extensively white – edges<br />

mottled<br />

• White mottled body spots with<br />

ticking and roaning<br />

• Extensively marked faces with<br />

white chin<br />

• Polygenic trait<br />

• 1 sabino pattern test available –<br />

N/SB1 or SB1/SB1 – extensive<br />

white sabino but no lethal


Sabino Variations<br />

• Paint pattern but occurs in many breeds


Splashed White<br />

• Legs, body and face<br />

are white<br />

• Edges of markings<br />

are crisp<br />

• Dipped into white<br />

paint


Dilution Factors<br />

• Cream<br />

• Dun<br />

• Silver<br />

• Champagne


Cream Dilution<br />

• Caused by Dilution factor Cr at the cream locus<br />

• Incomplete dominant gene, which means that it<br />

is expressed to some degree when there is only<br />

one copy of the gene and to a greater degree<br />

when there are 2 copies<br />

• DNA test available<br />

• 1 copy of dilution factor N/Cr<br />

Dilutes only red to yellow<br />

Does not dilute black


Palomino<br />

ee N/Cr<br />

Chestnut


Buckskin<br />

EEAa or EeAa and N/Cr<br />

Bay


Sooty Buckskin<br />

EEAa or EeAa and N/Cr<br />

Shaded Bay


Smoky Black<br />

Ee or EE and aaN/Cr<br />

Both tested to carry the cream dilution factor<br />

Can produce palomino, buckskin and double<br />

dilutes even though it looks black


Cream Dilution<br />

• 2 copies of dilution factor Cr/Cr<br />

Dilutes red and black<br />

Pink skin and blue eyes (not albinos)<br />

Diluted Chestnut<br />

= Cremello<br />

Diluted Bay<br />

= Perlino


Cream Dilution<br />

• DNA-tested:<br />

TOto EE aa Cr/Cr<br />

Diluted Black<br />

= Smoky Cream


Grey vs. Cremello


Dun<br />

• Dilution Factor + Primitive Marking Factor: Linked<br />

• Primitive marks are the colour of the undiluted base<br />

colour<br />

• Simple dominant gene<br />

DNDN – dun<br />

DNdn – dun<br />

dndn – not dun<br />

• Dilutes all colours to a certain extent<br />

• Yellow colour more tan than cream dilution<br />

• Manes, tails and primitive markings colour of non-<br />

diluted base colour<br />

• No direct DNA test (zygosity(<br />

test based on pedigree<br />

and other markers)


Primitive Markings<br />

• List (dorsal stripe)<br />

• Zebra stripes<br />

• Withers stripe<br />

• Cobwebbing on face


Bay with dun gene – zebra<br />

dun<br />

Classic Fjord colour<br />

Dun Variations


Dun Variations<br />

Chestnut : orange<br />

+ red points<br />

Red Dun<br />

Black : mouse / smoky<br />

coloured horse with black<br />

points<br />

Grullo


Silver / Taffy (aus(<br />

aus)<br />

• Silver gene (Z) is a simple<br />

dominant<br />

• Dilutes black but not red<br />

• Results in colors that are frequently confused with<br />

chestnut, but that lack the redness of chestnut<br />

• Lightens manes, tails, and lower legs to flaxen or silver<br />

grey, or can leave them relatively unchanged<br />

• Gene has been identified and test is available<br />

N/N – no silver mutation present<br />

Z/N or Z/Z – silver mutation present


Silver Variantions<br />

N/Z or ZZ<br />

• Bay-based horses will have chocolate lower limbs with<br />

flaxen mane and tail and red body<br />

• Red Silver


Silver Variantions<br />

N/Z or ZZ<br />

• Black-based / Brown horses will be chocolate with flaxen<br />

mane and tail<br />

• Chocolate Silver or Silver Dapple


Silver Characteristics<br />

Progressive colour that changes with age<br />

Foals often have silver eyelashes


Silver Variations<br />

• Chestnut will not be affected but may be confused with<br />

bay silver<br />

Chestnut confirmed silver carrier


Champagne<br />

• Simple dominant gene that dilutes hair pigment from<br />

black to brown and red to gold<br />

• N/Ch and Ch/Ch<br />

• The skin of Champagne-diluted horses is<br />

pinkish/lavender toned and becomes speckled with age;<br />

the speckling is particularly noticeable around the eye,<br />

muzzle, under the tail<br />

• The eye color is blue-green at birth and darkens to<br />

amber as the horse ages.<br />

• DNA test is available


Champagne<br />

Variations<br />

•Chestnut (red) diluted to<br />

gold body colour with<br />

flaxen mane and tail<br />

•Bay diluted to a tan<br />

body color with brown<br />

points<br />

•Black to a darker tan<br />

body with brown points


Champagne Variations<br />

Pinkish skin<br />

Blue to amber eyes<br />

Speckles


<strong>Horse</strong> Colour can be confusing without<br />

genetic testing<br />

Palomino N/Cr<br />

Chocolate Silver<br />

Z/Z or N/Z<br />

Flaxen Chestnut


<strong>Horse</strong> Colour can be confusing without<br />

genetic testing<br />

Smoky Cream<br />

E a/a Cr/Cr<br />

Perlino<br />

E A Cr/Cr<br />

Champagne Grullo<br />

a/a DN Ch


White<br />

• No albinos<br />

• No W/W lethal<br />

• N/W true white<br />

• Spot and paint patterns – extensive<br />

• Grey – pigmented skin and eyes<br />

• Cremello and Perlino

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