HorseHorse CoatCoat ColoursColours andand MarkingsMarkings

Cindy Harper Onderstepoort Laboratory for Applied Veterinary Genetics BasicBasic ColoursColours

Black

Bay Chestnut GeneticGenetic ControlControl ofof thethe BasicBasic ColoursColours

 MelanocytesMelanocytes produceproduce melaninmelanin pigmentpigment  22 PigmentsPigments responsibleresponsible forfor coatcoat andand skinskin colourcolour –– eumelanineumelanin (black(black andand brown)brown) andand phaeomelaninphaeomelanin (red(red andand yellow)yellow)  ColourColour genesgenes controlcontrol eithereither thethe pigmentpigment producingproducing cellcell oror pigmentpigment productionproduction  22 genesgenes controlcontrol thethe mainmain colourcolour switchesswitches inin horseshorses ExtensionExtension (E)(E) andand AgoutiAgouti (A)(A) GeneticsGenetics

Locus (address of a gene and each has a name) occurs on a pair of chromosomes – 1 from sire and 1 from dam Sire Dam Form of gene (allele) on 1 chromosome of pair can be same as on other – homozygosity Or different – heterozygosity

Different – dominant and recessive where 1 allele is expressed and other is not

Function: Gene that codes for protein

Protein: Effect e.g. stimulates melanocyte to produce eumelanin

Chromosome pair Result: Black horse TheThe ExtensionExtension Gene/LocusGene/Locus (E)(E)

 Difference between black and red lies in the action of 1 gene – MC1R  Allele symbols are E and e E extends black (eumelanin) in coat e extends red (phaeomelanin) in coat Combination of alleles at the extension locus:

EE Allows black in the coat: Black, brown, bay, Ee buckskin, grullo

Black in the skin but not in the coat: Chestnut, ee palomino BlackBlack PatternPattern TheThe AgoutiAgouti GeneGene // LocusLocus (A)(A)

AA Black pattern limited to the legs , mane and tail Aa

aa Black distributed uniformly through the coat

The combination of alleles at the extension and agouti genes / loci control the basic colour of the horse InteractionInteraction betweenbetween ExtensionExtension andand AgoutiAgouti

EEAA EEAa Black in coat Bay, Brown EeAA Black at the points EeAa

EEaa Black in coat Eeaa Black throughout coat Black,

eeAa eeAA Only red in the coat coat Chestnut, eeaa RedRed FactorFactor (e)(e)

 ExtensionExtension locuslocus –– 22 allelesalleles EE andand ee eeee breedingbreeding principlesprinciples Chestnut + chestnut = all chestnut

ee

e ee ee

e ee ee RedRed FactorFactor ((EeEe)) andand BlackBlack PatternPattern factorfactor ((AaAa)) chestnut + chestnut = All chestnut Sire: eeAa Extension (red) locus chestnut dominant over the Agouti (black) locus eA ea

ea eeAa eeaa

Dam: eeaa chestnut ea eeAa eeaa RedRed FactorFactor ((EeEe)) andand BlackBlack PatternPattern factorfactor ((AaAa))

Sire: EEaa black

Ea Ea eA EeAa EeAa Bay Bay eA EeAa EeAa

Dam: eeAA chestnut Bay Bay RedRed FactorFactor ((EeEe)) andand BlackBlack PatternPattern factorfactor ((AaAa))

Sire: Eeaa black

Ea ea Ea EEaa Eeaa Black Black ea Eeaa eeaa Dam: Eeaa black Black Chestnut BreedingBreeding BlackBlack

 AvoidAvoid recessiverecessive e!e! GeneticGenetic testtest forfor E/eE/e IsIs thisthis aa truetrue blackblack ((aaaa)) oror darkdark baybay // brownbrown ((AaAa)?)? GeneticGenetic testtest forfor A/aA/a PrinciplePrinciple Each horse has all the genes that can possibly code for any colour, BUT an individual allele combination that in total gives it a specific appearance!

Extension Locus Agouti Locus Cream Locus Grey Locus Tobiano Locus E e A A CR N g g TO N

1 2 3 4 5

Genotype: E/e A/A N/CR g/g N/TO

Phenotype: Diluted Bay (Buckskin) Non- grey with a Tobiano Paint pattern WhatWhat colourcolour?? BasicBasic ColourColour ModificationModification SootySooty // ShadedShaded BlackBlack hairshairs betweenbetween coatcoat hairshairs BayBay –– toplinetopline toto extensiveextensive coveringcovering mostmost ofof thethe bodybody BasicBasic ColourColour ModificationModification SootySooty // ShadedShaded BayBay –– extensiveextensive shadingshading ““BrownBrown”” HowHow toto distinguishdistinguish fromfrom truetrue black?black? GeneticGenetic testtest aaaa –– blackblack // AaAa oror AAAA -- brownbrown TheThe BrownBrown GeneGene

 ThereThere isis aa brownbrown genegene –– (TYRP1)(TYRP1) dilutesdilutes blackblack toto chocolatechocolate  MostMost obviousobvious inin dogs,dogs, butbut notnot commoncommon colourcolour inin horseshorses andand chocolatechocolate andand dundun horseshorses areare causedcaused byby otherother genesgenes WhenWhen isis aa horsehorse Brown?!Brown?!

 BrownBrown inin horseshorses isis aa termterm usedused toto describedescribe aa shadeshade ofof baybay inin horses.horses.  SomeSome breedersbreeders describedescribe allall baysbays withwith shadingshading // sootinesssootiness asas BrownBrown  SomeSome breedersbreeders describedescribe allall baysbays regardlessregardless ofof shadingshading asas baysbays  MostMost commonlycommonly breedersbreeders describedescribe thethe dark,dark, extensivelyextensively shadedshaded baybay asas brownbrown andand allall otherother baysbays asas baybay  Heritability?Heritability? BrownBrown HeritabilityHeritability

 Some believe that brown can be bred and is in fact a sub-division of the agouti locus or extension locus (At or EB)  Black is allowed in the coat and is more extensive than the points in a bay  This would support the proposal that brown (“extensive bay”) is heritable and “breedable” ColourColour termsterms

 TermsTerms thatthat describedescribe aa phenotypephenotype –– whatwhat youyou seesee  DependDepend onon breedbreed // societysociety // countrycountry // individualindividual  OnlyOnly rightright oror wrongwrong isis toto findfind andand testtest thethe actualactual geneticgenetic control!control!  FEIFEI rulebookrulebook statesstates thatthat thethe definitiondefinition ofof colourcolour differsdiffers accordingaccording toto country.country. BasicBasic ColourColour ModificationModification SootySooty // ShadedShaded

ChestnutChestnut –– usuallyusually distributeddistributed throughoutthroughout thethe coatcoat LiverLiver ChestnutChestnut BasicBasic ColourColour ModificationModification MealyMealy

 MealyMealy causescauses lighterlighter areasareas onon thethe belly,belly, muzzle,muzzle, innerinner legs,legs, andand overover thethe eyes.eyes. ItIt isis usuallyusually ignoredignored inin colorcolor description.description.  BlackBlack -- SealSeal brownbrown (test(test aaaa isis modifiedmodified blackblack // AaAa oror AAAA isis baybay withwith lotslots ofof shading)shading)  ChestnutChestnut toto sorrelsorrel forfor breedersbreeders ofof draftdraft horseshorses MealyMealy

Dun

Bay BayBay

 BlackBlack PointsPoints

 LegsLegs

 EarEar tipstips

 ManeMane

 TailTail VariationsVariations ofof BayBay BlackBlack

• No Brown in coat • White markings are allowed •Genetic test aa vs Aa or AA and EE or Ee FeatureFeature ofof BayBay vsvs BlackBlack

 AA blackblack horse,horse, eveneven withwith aa sunsun--bleachedbleached hairhair coatcoat willwill havehave solidsolid blackblack hairshairs aroundaround thethe eye.eye.

Bay Black ChestnutChestnut

ee e ee ee e ee ee

Recessive traits are expressed phenotypically when in homozygous form! Red coat throughout – no black points. ChestnutChestnut ModificationsModifications

Liver

Flaxen

Flaxen and mealy WhiteWhite onon basicbasic coatcoat

 AnyAny whitewhite oror whitewhite patternpattern isis SUPERIMPOSEDSUPERIMPOSED onon aa basicbasic colourcolour  CoverCover thethe wholewhole oror partpart ofof thethe horsehorse  PatternPattern –– namename GreyGrey RoanRoan RoaningRoaning SpottingSpotting PaintsPaints WhiteWhite markingsmarkings GreyGrey  BornBorn anyany colourcolour –– becomesbecomes greygrey  UsuallyUsually startsstarts onon headhead andand isis progressiveprogressive  SpeedSpeed ofof greyinggreying individualindividual  GradualGradual processprocess –– completelycompletely whitewhite withwith pigmentedpigmented skinskin GreyGrey BreedingBreeding

 DominantDominant traittrait GGGG andand GgGg –– alwaysalways greygrey i.e.i.e. aa horsehorse doesdoes notnot carrycarry aa hiddenhidden greygrey genegene  AA greygrey foalfoal mustmust havehave atat leastleast 11 greygrey parent!parent! GG  HomozygousHomozygous greygrey ++ nonnon Gg greygrey 100%100% GreyGrey g Gg g Gg Gg GreyGrey BreedingBreeding

 A horse can have any combination of base coat genes, but G overrides all e/e a/a N/RN to/to C/C G/g = GREY  Grey is going to obliterate any other colour pattern  2 greys can  produce a non-grey Gg  DNA Test available G GG Gg

g Gg gg GreyGrey VariationsVariations  VariationsVariations ofof greygrey cancan givengiven differentdifferent names:names: Rose grey

Fleabitten grey Steel grey

Dapple grey RoanRoan  PermanentPermanent colourcolour,, whitewhite doesdoes notnot progressprogress withwith age!age!  DarkDark headhead andand limbslimbs  CharacteristicCharacteristic invertedinverted ““VV”” aboveabove kneesknees RoanRoan GeneticsGenetics  RNRN isis causedcaused byby aa dominantdominant gene.gene. RNrnRNrn oror rnrnrnrn (not(not roan)roan) –– nono testtest yetyet  THUS:THUS: AA roanroan mustmust havehave 11 roanroan parent!parent!  HomozygousHomozygous dominantdominant roanroan RNRNRNRN == lethallethal resorptionresorption?? RoanRoan VariationsVariations

Chestnut Roan

Blue Roan RabicanoRabicano // RoaningRoaning

 Rabicano, also called white ticking or roaning, is characterized by limited roaning in a specific pattern, usually in the flank, sides and the tailhead  Also in breeds which do not possess any true roan Thoroughbreds and Arabians SpotsSpots

 THETHE LEOPARDLEOPARD COMPLEXCOMPLEX  ProducedProduced byby aa thethe leopardleopard genegene complexcomplex ((LpLp))  ItIt isis aa dominantdominant traittrait –– patternspatterns producedproduced byby modifiermodifier genesgenes  NotNot allall horseshorses withwith thethe dominantdominant leopardleopard alleleallele ((LpLp)) willwill bebe spottedspotted butbut indicatorsindicators ofof thisthis genegene include:include:  WhiteWhite sclerasclera  MottledMottled skinskin  StripedStriped hooveshooves LeopardLeopard BreedingBreeding

 OccursOccurs inin manymany breedsbreeds butbut inin somesome itit isis aa fixedfixed characteristiccharacteristic Appaloosa,Appaloosa, KnapstrupKnapstrup,, NorikerNoriker  DominantDominant LpLp alleleallele expressesexpresses aa patternpattern  PatternPattern dependsdepends onon modifiersmodifiers  HorseHorse withwith aa specificspecific patternpattern cancan produceproduce thethe wholewhole rangerange ofof patternspatterns dependingdepending onon thethe modifiersmodifiers inin itsits genegene complexcomplex  NoNo specificspecific testtest LeopardLeopard PatternsPatterns  LeopardLeopard BlanketBlanket VarnishVarnish RoanRoan  NotNot RnRn oror GG  LpLp spottingspotting complexcomplex genegene withwith characteristicscharacteristics andand maymay havehave leopardleopard spotsspots  MottledMottled skin,skin, colorcolor mainlymainly onon bonybony pointspoints (on(on thethe face,face, usuallyusually inin aa distinctdistinct VV onon thethe bridgebridge ofof thethe nose;nose; onon thethe cheeks,cheeks, pointpoint ofof shoulder,shoulder, elbows,elbows, knees,knees, pointpoint ofof hips,hips, hock)hock) andand itit cancan bebe seasonalseasonal asas wellwell  RoansRoans (RN)(RN) areare roanroan fromfrom birth,birth, varnishvarnish roansroans areare bornborn quitequite solidsolid withwith somesome spotsspots andand "roan"roan out"out" asas theythey ageage VarnishVarnish RoanRoan VariationsVariations LeopardLeopard VariationsVariations

Small Blanket Extensive Solid Blankets

Leopards with various sized spots Extensive Spotted Blanket or Near Leopard PaintsPaints  BasicBasic colourcolour withwith aa whitewhite patternpattern superimposedsuperimposed  PatternsPatterns areare controlledcontrolled byby separateseparate genesgenes andand areare heritableheritable  ExtentExtent ofof patternpattern cancan varyvary TobianoTobiano

 Most legs white  White crosses the topline  General head markings (may have no head markings)  Mixed tail  Regular Edges  Dominant gene TO/TO or N/TO  Direct Genetic Test available TobianoTobiano VariationsVariations FrameFrame OveroOvero

 DarkDark legslegs  WhiteWhite patchespatches onon thethe sidessides  IrregularIrregular EdgesEdges  ExtensiveExtensive headhead markingsmarkings  TailTail oneone colourcolour FrameFrame OveroOvero OLWSOLWS

 Frame Overo is associated with Lethal White Foal Syndrome (LWF)  Mutation in gene supposedly produces frame overo – O/O  Test for this mutation  Some solids carry the O mutation (N/O)  N/O x N/N – always to avoid lethal  O/O solid white foal with incomplete intestinal development SabinoSabino

 Legs extensively white – edges mottled  White mottled body spots with ticking and roaning  Extensively marked faces with white chin  Polygenic trait  1 sabino pattern test available – N/SB1 or SB1/SB1 – extensive white sabino but no lethal SabinoSabino VariationsVariations  PaintPaint patternpattern butbut occursoccurs inin manymany breedsbreeds SplashedSplashed WhiteWhite

 Legs,Legs, bodybody andand faceface areare whitewhite  EdgesEdges ofof markingsmarkings areare crispcrisp  DippedDipped intointo whitewhite paintpaint DilutionDilution FactorsFactors

 CreamCream  DunDun  SilverSilver  ChampagneChampagne CreamCream DilutionDilution

 CausedCaused byby DilutionDilution factorfactor CrCr atat thethe creamcream locuslocus  IncompleteIncomplete dominantdominant gene,gene, whichwhich meansmeans thatthat itit isis expressedexpressed toto somesome degreedegree whenwhen therethere isis onlyonly oneone copycopy ofof thethe genegene andand toto aa greatergreater degreedegree whenwhen therethere areare 22 copiescopies  DNADNA testtest availableavailable  11 copycopy ofof dilutiondilution factorfactor N/CrN/Cr DilutesDilutes onlyonly redred toto yellowyellow DoesDoes notnot dilutedilute blackblack PalominoPalomino eeee N/CrN/Cr

Chestnut BuckskinBuckskin EEAaEEAa oror EeAaEeAa andand N/CrN/Cr

Bay SootySooty BuckskinBuckskin EEAaEEAa oror EeAaEeAa andand N/CrN/Cr

Shaded Bay SmokySmoky BlackBlack EeEe oror EEEE andand aaNaaN/Cr/Cr

Both tested to carry the cream dilution factor Can produce palomino, buckskin and double dilutes even though it looks black CreamCream DilutionDilution  2 copies of dilution factor Cr/Cr Dilutes red and black Pink skin and blue eyes (not albinos)

Diluted Chestnut = Cremello

Diluted Bay = Perlino CreamCream DilutionDilution

 DNADNA--tested:tested: TOtoTOto EEEE aaaa Cr/CrCr/Cr

Diluted Black = Smoky Cream GreyGrey vs.vs. CremelloCremello DunDun

 Dilution Factor + Primitive Marking Factor: Linked  Primitive marks are the colour of the undiluted base colour

 Simple dominant gene DNDN – dun DNdn – dun dndn – not dun

 Dilutes all colours to a certain extent  Yellow colour more tan than cream dilution  Manes, tails and primitive markings colour of non- diluted base colour  No direct DNA test (zygosity test based on pedigree and other markers) PrimitivePrimitive MarkingsMarkings

•• ListList (dorsal(dorsal stripe)stripe) •• ZebraZebra stripesstripes •• WithersWithers stripestripe •• CobwebbingCobwebbing onon faceface DunDun VariationsVariations

Bay with dun gene – zebra dun Classic Fjord colour DunDun VariationsVariations

Chestnut : orange Black : mouse / smoky + red points coloured horse with black Red Dun points Grullo SilverSilver // TaffyTaffy ((ausaus))

 Silver gene (Z) is a simple dominant  Dilutes black but not red  Results in colors that are frequently confused with chestnut, but that lack the redness of chestnut  Lightens manes, tails, and lower legs to flaxen or silver grey, or can leave them relatively unchanged  Gene has been identified and test is available N/N – no silver mutation present Z/N or Z/Z – silver mutation present SilverSilver VariantionsVariantions N/ZN/Z oror ZZZZ  Bay-based horses will have chocolate lower limbs with flaxen mane and tail and red body  Red Silver SilverSilver VariantionsVariantions N/Z or ZZ  Black-based / Brown horses will be chocolate with flaxen mane and tail  Chocolate Silver or Silver Dapple SilverSilver CharacteristicsCharacteristics

Progressive colour that changes with age

Foals often have silver eyelashes SilverSilver VariationsVariations

 Chestnut will not be affected but may be confused with bay silver

Chestnut confirmed silver carrier ChampagneChampagne

 Simple dominant gene that dilutes hair pigment from black to brown and red to gold  N/Ch and Ch/Ch  The skin of Champagne-diluted horses is pinkish/lavender toned and becomes speckled with age; the speckling is particularly noticeable around the eye, muzzle, under the tail  The eye color is blue-green at birth and darkens to amber as the horse ages.  DNA test is available ChampagneChampagne VariationsVariations

•Chestnut (red) diluted to gold body colour with flaxen mane and tail

•Bay diluted to a tan body color with brown points

•Black to a darker tan body with brown points ChampagneChampagne VariationsVariations

Pinkish skin

Blue to amber eyes

Speckles HorseHorse ColourColour cancan bebe confusingconfusing withoutwithout geneticgenetic testingtesting

Palomino N/Cr

Chocolate Silver Z/Z or N/Z

Flaxen Chestnut HorseHorse ColourColour cancan bebe confusingconfusing withoutwithout geneticgenetic testingtesting

Perlino Smoky Cream E A Cr/Cr E a/a Cr/Cr

Champagne Grullo a/a DN Ch WhiteWhite

 NoNo albinosalbinos  NoNo W/WW/W lethallethal  N/WN/W truetrue whitewhite  SpotSpot andand paintpaint patternspatterns –– extensiveextensive  GreyGrey –– pigmentedpigmented skinskin andand eyeseyes  CremelloCremello andand PerlinoPerlino