Understanding the words on this site
Horse and genetics glossary
A word slowing you down? Find its meaning here, with an example where useful and links to fuller explanations for selected topics. Dotted underlines in the articles lead to these definitions.
Equids and counting animals
Equid
An animal in the horse family, which includes horses, donkeys and zebras. Ponies are horses; mules and hinnies are also equids. In a population figure, check which of these animals the source includes.
Mule
The offspring of a male donkey and a mare. A mule has parents from two different species. The reverse cross, between a stallion and a female donkey, produces a hinny.
Hinny
The offspring of a stallion and a female donkey. It differs from a mule in which species the father and mother belong to. Both are horse–donkey hybrids.
Census
A systematic count within a defined area, period and set of categories. An agricultural census counts animals within its agricultural coverage, which may leave out horses kept elsewhere. Its total is not automatically a count of every equid in a country.
Breeding and registration
Identification transponder
A small electronic device carrying a code read by a suitable scanner. For equids, this is usually a microchip implanted under the skin. Its code links an animal to identification records; it does not contain its genome or a complete pedigree.
Animal traceability
The ability to follow an animal’s identity and movements through linked records. For an equid, an identifier, an electronic device, a passport and a database can all contribute to this system. Traceability alone does not describe the animal’s pedigree or establish its breed.
Stud farm
A place devoted to breeding horses and raising youngstock. France’s former royal and national studs also supplied stallions for breeders to use.
Studbook
A studbook records the identity and known ancestry of horses, ponies or donkeys belonging to a recognised breed or population. It is often held as a database today. Each studbook has its own entry rules: some allow specified crosses, while others require parents that are already registered.
Studbook registers and sections
A studbook may divide animals into registers or sections according to their ancestry and the requirements they meet. The letters A and B do not mean the same thing in every breed. Registering a foal and approving an adult for breeding are also separate procedures.
Breeding programme
A breeding programme sets out a breed’s breeding goals and how they are to be pursued. It describes desired characteristics, which animals may breed and the assessments used. The document’s date identifies its version; it does not mean the breed was created that year.
Breed standard
A breed standard describes the characteristics sought in a breed, such as body proportions, height, colour or movement. It provides a reference for assessments. A standard describes breeding aims; it does not mean that every animal in the breed looks the same.
Pedigree and ancestry
A pedigree lists an animal’s known parents and ancestors, like a family tree. Ancestry means those family origins. These records make it possible to trace families and crosses through generations, provided the recorded parentage is reliable.
Parentage
Parentage is the relationship between an animal and its parents. Establishing a foal’s parentage means identifying its dam and sire. DNA testing can check whether the parents declared by the breeder are compatible with the foal’s genetic profile.
DNA parentage test
A DNA parentage test compares genetic markers in a foal with those of its declared parents to check whether that relationship is compatible. It helps verify pedigree records. It is not, by itself, a test for inherited diseases.
Breeding animal
A breeding animal is an animal used to produce offspring. In horses, this may be a stallion or a mare; a mare used for breeding is called a broodmare. Some studbooks require assessments or tests before accepting an animal for breeding.
Breeding approval
Breeding approval is a breed organisation’s decision to accept an animal for breeding under its rules. It may depend on ancestry, conformation, performance or test results. Studbook registration therefore does not always mean the animal is approved to breed.
Estimated breeding value
An estimated breeding value predicts qualities an animal may pass on to its offspring. It may use the animal’s performance, relatives’ results and, in some methods, DNA data. It helps compare breeding animals but cannot guarantee a future foal’s performance.
Purebred animal
A purebred animal meets the ancestry and registration requirements set for its breed. Appearance alone cannot establish that status. The term describes membership of a breeding population; it does not mean its DNA is identical to that of every other animal in the breed.
Crossbreeding
Crossbreeding combines parents from different breeds or populations. For example, a mare of one breed may be mated to a stallion of another. Any studbook that might register the foal applies its own rules; a cross does not automatically qualify for registration.
Inbreeding coefficient
The inbreeding coefficient, often written F, estimates the probability that an individual’s two copies at a genetic location trace back to the same ancestral copy. The calculation depends on the data and method. An F of 12.5% does not mean a 12.5% disease risk.
Inbreeding depression
Inbreeding depression is a decline in average performance, such as reproduction or survival, associated with inbreeding in a population. It can arise in part when harmful variants occur in two copies. It does not predict the condition of a particular horse.
Conformation and movement
Conformation
Conformation describes the shape and proportions of an animal’s body, such as back length, neck shape and limb alignment. Breeders assess the horse standing and in motion to understand its physical build.
Withers
The withers are the raised area at the base of the neck, above the shoulders. A horse’s height is measured from the ground to the top of the withers, rather than to its head. A height of 1.60 m at the withers refers to this measurement.
Limb alignment
Limb alignment describes how the legs are positioned and how the feet sit beneath the body. It is assessed from the front, side and rear. This helps show how the horse bears weight and moves.
Feathering
Feathering is the long hair around the lower legs and fetlocks, the rounded joints above the hooves, sometimes extending over the hooves. It is particularly abundant in some draught breeds and the Irish Cob. The word describes hair, not the shape of the bones or joints.
Cannon region
The cannon region lies between the knee and fetlock in a foreleg, or between the hock and fetlock in a hind leg. Cannon circumference measures around this region. It gives information about limb build, but does not measure overall soundness on its own.
Croup
The croup is the upper rear part of the body, between the back and the base of the tail. Its length, slope and muscle development are among the features assessed when describing a horse’s conformation.
Gaits
Gaits are the different ways a horse moves. Walk, trot and canter or gallop differ in the sequence and rhythm of hoof contact with the ground. Some breeds also perform additional gaits, such as the Icelandic horse’s tölt.
Coat colour
Coat colour describes the colour of a horse’s body hair, mane and tail, together with their patterns and distribution. It can change with age. For example, a grey horse is born coloured and gradually develops more white hair.
Hand (height unit)
A unit used to measure a horse’s height at the withers. One hand equals four inches, or 10.16 cm. The notation 14.1 means fourteen hands plus one inch, about 1.45 m; the digit after the point counts inches, not tenths of a hand.
Forelimb
Either of the horse’s front legs, on the shoulder side of its body. Identifying which forelimb touches the ground helps explain the footfall sequence of a gait.
Hindlimb
Either of the horse’s rear legs, beneath the hindquarters. The hindlimbs contribute to forward thrust and balance as the horse moves.
Genetics and populations
Lineage
A group of animals connected by shared ancestry. Researchers can identify a lineage by comparing DNA, while breeders can follow a family through pedigrees. An ancient lineage is not necessarily a modern breed: breeds and their registries take shape at different times.
DNA
DNA is the molecule that carries genetic information in cells. A foal inherits genetic information from each parent. A DNA test examines selected parts of this molecule to answer a particular question, such as checking parentage or looking for a variant.
Gene
A gene is a stretch of DNA that contributes to how the body works, including instructions for making particular molecules. A gene can have different versions. Horses still have the gene when they do not carry a particular variant targeted by a test.
Allele
An allele is a version of a DNA sequence at a particular location. For most genes, a horse has two copies, one inherited from each parent. Those copies may be the same allele or different alleles.
Genetic variant
A genetic variant is a difference in a DNA sequence. Depending on the variant, it may alter coat colour, increase disease risk or have no known effect. Finding a variant therefore does not automatically mean a horse is ill.
Genotype
A genotype describes the DNA versions an animal has at the location being examined. In a test result, it often specifies the two copies being tested. It describes DNA; appearance and clinical signs are separate observations.
Phenotype
A phenotype is an animal’s observable characteristics, such as coat colour, height or signs of disease. It depends on DNA and, for many traits, also on age and environment. Two horses with the same result for one DNA test can therefore differ in appearance or health.
Dominant inheritance
A variant is dominant for a particular effect when that effect can occur with one copy. Dominant does not mean more common or more severe. Depending on the trait or condition, horses carrying the variant may show different effects.
Recessive inheritance
For a simple recessive trait that is not sex-linked, the effect appears when the horse receives two copies of the variant, one from each parent. A horse with one copy can pass on the variant without showing that effect. Two parents without disease signs can therefore produce an affected foal.
Unaffected carrier
For a particular recessive condition, an unaffected carrier has one copy of the variant and can pass it on without having that condition. This describes the specific variant, not the horse’s overall health. It does not automatically describe an outwardly healthy horse carrying a dominant disease variant.
Inbreeding
Inbreeding results from mating animals that share ancestors. It increases the chance that a foal inherits two copies of the same DNA version from a common ancestor. This can increase the occurrence of recessive conditions and reduce genetic diversity.
Genetic diversity
Genetic diversity is the variety of DNA versions within a population. Keeping several families contributing to breeding helps preserve that variety. A large headcount alone is not enough if nearly all the horses descend from the same few breeding animals.
Study population
A population is the group of animals considered for a particular question. It might mean a breed worldwide, registered breeding animals in one country or horses on a farm. To interpret a figure, check which animals, place and period it covers.
Sample or cohort
A sample may mean a group of animals selected for a study or biological material collected for analysis, such as blood or hair. A cohort is a defined group, often followed over time. Results from the animals studied do not necessarily represent their whole breed.
Locus
A locus is a specific location in DNA, like an address. The plural is loci. Two alleles at the same locus are two possible versions at that address.
Homozygous
A horse is homozygous when it has two identical alleles at the locus being examined. For example, E/E describes this combination at Extension, the gene MC1R.
Heterozygous
A horse is heterozygous when it has two different alleles at the locus being examined. For example, E/e describes this combination at Extension, the gene MC1R.
Epistasis
Epistasis is an interaction in which one locus changes or hides the effect of another. For example, Agouti cannot visibly change the distribution of black pigment in a chestnut horse because its hair produces none.
Penetrance
Penetrance is the proportion of individuals with a particular genotype who actually show the associated trait. If some do not show it, penetrance is incomplete. The genotype then cannot predict the observed outcome with certainty.
Expressivity
Expressivity describes how a trait appears in individuals who show it. With the same genetic combination, disease signs may differ in severity, or the amount of white in a coat may vary.
Haplotype
A haplotype is a set of variants carried on the same copy of a chromosome. They may be inherited together. This arrangement helps explain why nearby variants do not always pass to offspring independently.
Chromosome
A chromosome is a long DNA molecule packaged with proteins. It carries many genes. In body cells, chromosomes usually come in pairs, with one copy inherited from each parent.
Autosomal
An autosomal gene is on a chromosome other than the sex chromosomes X and Y. A horse usually has two copies of that gene, one from each parent. An autosomal trait can therefore affect both males and females.
Genome
The genome is an organism’s complete set of genetic information. A genomic analysis examines many locations across that information. It can cover more than one gene without necessarily testing every possible cause of disease.
Genetic linkage
Genetic linkage is the tendency for nearby regions of the same chromosome to be inherited together. Multiplying their inheritance probabilities as if they were independent can give an incorrect result.
Recombination
Recombination exchanges segments between the two chromosomes of a pair during the formation of reproductive cells. It creates new combinations of genetic versions and can separate variants that were previously inherited together.
Genetic marker
A genetic marker is an identifiable signpost in DNA. It can help compare horses, check parentage or track a region associated with a trait. The marker is not necessarily the change that causes the trait.
Mutation
A mutation is a change in the DNA sequence. It may first arise in an individual or be passed to offspring. The word alone does not mean that the change causes disease.
Compound heterozygote
A compound heterozygote has two different variants of the same gene, one on each copy inherited from the parents. A Cr/Prl horse, for example, has one Cream version and one Pearl version of SLC45A2. It passes one or the other to a foal.
Incomplete dominance
Incomplete dominance means that two different alleles at a location produce an effect distinct from either matching pair. For Cream, one copy and two copies of the variant lighten the coat differently.
Sample
In a laboratory, a sample is the material being analyzed, such as hairs with roots. In a study, the word can also mean the group of individuals examined. Findings in that group do not automatically describe the entire breed.
Allele frequency
Allele frequency is the share of a particular allele among all copies counted at the same DNA location in a group. It differs from the proportion of horses carrying it: one horse may contribute one or two copies to the count.
Run of homozygosity
A run of homozygosity, or ROH, is a long DNA region where both chromosomes have the same versions at the markers examined. The proportion of the genome covered by these runs can help estimate inbreeding. Results depend on the markers and thresholds used.
Deletion
A deletion is the loss of a DNA segment. It can remove a few letters of the sequence or a much longer region. Its effects depend on what is missing and the role of that region.
Insertion
An insertion adds material to the DNA sequence. Even a small addition can sometimes change how a gene’s instructions are read. Its effect depends on where the addition occurs.
Chromosomal inversion
A chromosomal inversion is a rearrangement that reverses a DNA segment. Depending on its location, it can affect how nearby genes work. Tobiano is associated with an inversion near KIT.
SNP
A SNP is variation in a single DNA letter at a particular position. Many SNPs can be examined together as genetic markers. Measuring a SNP does not mean that it causes disease.
Equestrian disciplines
Doma vaquera
A Spanish riding tradition associated with working cattle on horseback. It develops the responsiveness and manoeuvrability needed for that work. Its sporting form brings exercises derived from those rural tasks into an arena, under rules separate from those of classical dressage.
Tbourida
A Moroccan equestrian tradition in which a troupe of riders performs a parade and a galloping charge with blank rifle fire. Inscribed as UNESCO intangible cultural heritage in 2021.
Dressage
Dressage is a discipline in which horse and rider perform a planned sequence of precise movements. Judges assess qualities including regularity of the gaits, balance and execution. In a broader sense, dressage also refers to the horse’s training.
Eventing
Eventing combines three tests performed by the same horse and rider: dressage, a cross-country course over obstacles in varied terrain, and show jumping. It requires a range of abilities, including balance, stamina and accuracy.
Driving
In driving, one or more equids pull a vehicle controlled by a driver. It may be used for leisure, transport or competition.
Endurance riding
Endurance riding is a racing discipline over an outdoor route, with veterinary checks assessing horses during the event. When describing an animal more generally, endurance can also mean its ability to sustain effort over time.
Fox trot
A four-beat gait associated with the Missouri Fox Trotter. A front foot lands just before the opposite hind foot, instead of the diagonal pair landing together as in an ordinary trot. That separation reduces the bounce felt by the rider.
Flat foot walk
An active, regular four-beat walk, with each foot landing separately. It is one of the gaits assessed in Missouri Fox Trotters.
Running walk
The Tennessee Walking Horse’s ground-covering four-beat gait, faster than an ordinary walk. The hind feet land beyond the tracks left by the front feet, while the head nods in time with the movement.
Pace
A two-beat gait in which the legs on one side move together, followed by the legs on the other side. In a trot, the legs instead move in opposite diagonal pairs. Some Standardbred races are run at the pace.
Sulky
A small, lightweight two-wheeled vehicle pulled by a horse, especially in harness racing. The driver sits in the sulky and guides the horse with reins.
Health and genetic testing
Polysaccharide storage myopathy type 1 (PSSM1)
Stiffness after work, muscle pain or reluctance to move can have several causes. PSSM1 is one inherited explanation. It changes how muscle makes and stores glycogen, a reserve of energy. A DNA test can identify the responsible variant, while a veterinary assessment establishes what is happening in the individual horse. A genetic result and a clinical examination answer different, complementary questions.
Read the full explanation: Polysaccharide storage myopathy type 1 (PSSM1)
Hyperkalemic periodic paralysis (HYPP)
Muscle twitching, sudden weakness and an apparently normal horse afterwards can be part of HYPP. This inherited disorder changes the electrical signals involved in muscle contraction. Some episodes are subtle, while severe attacks can threaten breathing and life. DNA testing identifies a specific variant; it cannot tell an owner when the next episode will happen or how serious it will be.
Read the full explanation: Hyperkalemic periodic paralysis (HYPP)
Hereditary equine regional dermal asthenia (HERDA)
Skin that tears easily, wounds under the saddle and extensive scarring can reveal HERDA. This inherited condition weakens supporting tissue, most visibly in the skin. A foal can appear normal before lesions develop. DNA testing identifies the relevant variant and distinguishes an unaffected carrier from a horse with the two copies responsible for disease. That distinction matters both for the horse and for future foals.
Read the full explanation: Hereditary equine regional dermal asthenia (HERDA)
Fragile foal syndrome type 1 (WFFS / FFS)
Fragile foal syndrome type 1, or FFS, is a severe inherited disorder of the tissues that support the body. Affected foals may be born with extremely delicate skin and extensive injuries. Before breeding, a DNA test can establish whether the mare and stallion carry the FFS variant. It also helps vets investigate this disease in a foal with suspicious signs.
Read the full explanation: Fragile foal syndrome type 1 (WFFS / FFS)
Severe combined immunodeficiency (SCID)
A foal with SCID can look normal at birth and later develop overwhelming infections. This inherited condition prevents essential parts of its immune defenses from working. A DNA test distinguishes a horse without the tested variant, an unaffected carrier and an affected foal.
Read the full explanation: Severe combined immunodeficiency (SCID)
Cerebellar abiotrophy (CA)
A foal with head tremors or poor balance has not necessarily been injured in a fall. Cerebellar abiotrophy, or CA, is an inherited condition affecting coordination. Signs vary considerably, and a genetic result needs to be considered alongside examination of the horse.
Lethal white overo syndrome (LWO)
A white foal does not necessarily have a fatal condition. Lethal white overo, or LWO, is a specific intestinal disorder caused by two copies of the frame overo variant. One copy of the same variant can change the coat without causing this intestinal syndrome.
Read the full explanation: Lethal white overo syndrome (LWO)
Hoof wall separation disease (HWSD)
Hoof wall separation disease, or HWSD, weakens the hoof wall so that it splits, crumbles or separates, often in a young pony. It is best documented in Connemaras. Its inherited origin does not mean every Connemara is affected, or that every cracked hoof has this cause.
Read the full explanation: Hoof wall separation disease (HWSD)
Glycogen branching enzyme deficiency (GBED)
A very weak newborn foal can have many different illnesses. GBED is one particularly serious inherited cause, affecting the way cells build their energy reserve. It can also lead to pregnancy loss or stillbirth. The parents may nevertheless be healthy: a horse with one copy of the variant is unaffected by GBED but can pass that copy to a foal.
Read the full explanation: Glycogen branching enzyme deficiency (GBED)
Malignant hyperthermia (MH)
A horse can carry an RYR1 variant that makes a malignant hyperthermia episode more likely while appearing entirely healthy. This increased inherited risk is called genetic susceptibility. During an episode, the muscles become overactive, use excessive energy and generate dangerous heat. Certain anaesthetic drugs can trigger that reaction. DNA testing identifies the known equine variant. It cannot promise that an episode will occur, but provides information the veterinary team needs when planning a procedure.
MYH1-associated myopathy (MYHM)
Rapid muscle loss or a painful muscle episode without exercise may lead a veterinarian to investigate MYHM. The name covers two clinical presentations associated with a variant in MYH1. The MYHM test looks for a MYH1 variant that increases the risk of these muscle disorders. That increased risk is called genetic susceptibility. Having one or two copies of this variant does not mean the horse will necessarily develop disease. Keeping genetic risk separate from current health is essential when reading a report or making plans for the horse.
Lavender foal syndrome (LFS)
Lavender foal syndrome, or LFS, combines severe neurological disease with an often unusually pale coat. Affected foals may be unable to stand or nurse normally from birth. This fatal inherited condition is mainly documented in Arabians and Arabian crosses. Prevention depends on knowing both parents’ genetic results before mating.
Foal immunodeficiency syndrome (FIS)
A foal with FIS may appear normal at birth, then become weak, anemic and highly vulnerable to infections. Foal immunodeficiency syndrome affects red blood cell production as well as an essential part of the immune system. This fatal inherited disease is documented particularly in Fell and Dales ponies.
Read the full explanation: Foal immunodeficiency syndrome (FIS)
Junctional epidermolysis bullosa (JEB)
In a foal with junctional epidermolysis bullosa, ordinary pressure can cause serious wounds because the skin is not securely attached to underlying tissue. Two genetic forms are tested in horses, JEB1 and JEB2. Their clinical signs overlap, but they involve different genes and require separate interpretation.
Read the full explanation: Junctional epidermolysis bullosa (JEB)
Congenital stationary night blindness (CSNB)
A horse may move confidently in daylight yet see little when the light fades. Congenital stationary night blindness, or CSNB, is present from birth and affects vision in dim conditions. Two genetic causes can be investigated with separate tests: LP in TRPM1 and CSNB2 in GRM6.
Read the full explanation: Congenital stationary night blindness (CSNB)
Multiple congenital ocular anomalies (MCOA)
Silver can dilute black pigment in a horse’s coat, but the same variant can also affect eye development. The condition is called multiple congenital ocular anomalies, or MCOA. One and two copies have different usual effects, and a chestnut can carry the variant without showing its coat dilution.
Read the full explanation: Multiple congenital ocular anomalies (MCOA)
B4GALT7-associated Friesian dwarfism
The dwarfism described in Friesians is more than being a horse smaller than average. Parts of the skeleton grow differently: limbs are shortened and joints can be excessively flexible. This inherited form is associated with a B4GALT7 variant. Unlike several fatal foal disorders, it can be compatible with a good quality of life.
Read the full explanation: B4GALT7-associated Friesian dwarfism
Inherited hydrocephalus (B3GALNT2)
An unusually large head in a foal may reflect hydrocephalus: fluid accumulates within the developing brain’s cavities. A severe inherited form in Friesian horses is associated with a B3GALNT2 variant. It can also make delivery difficult for the mare. DNA testing is especially useful for identifying unaffected carriers before a mating.
Read the full explanation: Inherited hydrocephalus (B3GALNT2)
Skeletal atavism (SA)
Deforming limbs and increasing difficulty moving can reflect abnormal bone development. Skeletal atavism is one inherited condition investigated in Shetland ponies and described in miniature horses. Testing looks for two losses of DNA, Del1 and Del2. Small size alone is not the problem: the important change is how particular limb bones develop.
DNA test
A DNA test examines a sample for specific genetic information, such as a coat variant, a disease variant or parentage markers. Its result applies to what the laboratory actually tested. A negative result does not rule out every genetic condition.
Test panel
A test panel groups several genetic tests together. Its contents depend on the laboratory and the version offered. Read the list of tested variants: the panel’s name alone does not tell you which conditions or colors it covers.
Hereditary
A hereditary trait can pass from parents to offspring through genetic information. An inherited condition does not have to be visible at birth; its signs may appear later.
Congenital
A congenital condition is present at birth, even if it is discovered later. It may result from a genetic cause, the environment during pregnancy or several factors together. Congenital does not automatically mean hereditary.
Genetic predisposition
A genetic predisposition is a DNA characteristic that increases the likelihood of developing a condition. It does not mean that every horse with it will become ill. Other factors may contribute, depending on the condition.
Causal variant
A causal variant directly contributes to the trait being studied, rather than simply lying nearby in DNA. A pathogenic variant is involved in causing disease. Its consequences depend in part on the number of copies and the condition’s inheritance pattern.
Protein
A protein is a molecule made by cells using genetic instructions. Proteins have many jobs, including building tissues, carrying substances and enabling chemical reactions.
Enzyme
An enzyme speeds up a chemical reaction in the body. Most enzymes are proteins. A genetic change that disrupts an enzyme can affect how the body makes or uses particular substances.
Glycogen
Glycogen is a stored form of sugar found especially in muscles and the liver. The body can use it for energy. Some genetic conditions affect how it is made, stored or used.
Lethal
Lethal describes an effect that causes death. In genetics, the variant and combination matter: a variant may be compatible with life in one copy but lethal in two copies.
Myopathy
A myopathy is a disease affecting muscles. The term covers several possible causes, genetic or otherwise. It does not identify one specific condition or DNA test.
Melanoma
A melanoma is a tumor that develops from melanocytes, the pigment-producing cells. Gray horses are particularly affected, but coat color alone cannot diagnose a lump or predict how it will develop.
Coat colors, pigments and markings
Extension
Two chestnut-based parents produce a chestnut-based foal, while two bay horses can also have a chestnut foal. Extension explains this difference. Other genes can then change the coat color you see.
Agouti
A bay has a brown body with black mane, tail and lower legs. A black horse has black pigment over its body too. Agouti helps explain that distribution.
Cream
Cream can turn chestnut into palomino and bay into buckskin. With two copies, the coat becomes much paler. The inherited base still matters.
Pearl
A horse can carry Pearl without looking dilute. Two Pearl copies, or a Pearl copy paired with Cream, can change the coat substantially.
Dun
Dun changes how pigment is distributed within colored hairs. A dark stripe along the back is a useful clue, but a stripe on its own does not prove the horse has Dun dilution.
Champagne
Champagne lightens red and black pigment and also affects skin and eye color. A golden body alone is not enough to identify it.
Silver
Silver mainly changes black pigment. It can be invisible in a chestnut’s coat while still being inherited and associated with eye abnormalities.
Mushroom
Mushroom can turn a chestnut-based coat toward muted sepia tones. It is best documented in Shetland ponies and can resemble other dilutions.
Gray
A gray horse grows more white hairs over time while keeping the genetic information for its original base color. Its current appearance does not reveal all the variants it can pass on.
Tobiano
Tobiano produces white patches, often crossing the back. A horse can carry one or two copies of the associated DNA variant, and the amount of white does not reliably distinguish them.
Frame overo
A horse with one frame variant may have extensive white or almost none. A foal inheriting two copies develops lethal white syndrome and dies after birth because its intestine cannot function normally.
Sabino and Sabino 1
Sabino describes an appearance: irregular white markings, sometimes edged with mixed white hairs. Sabino 1, or SB1, is one identified DNA variant that can produce it; other variants can look similar.
Splashed white
Splashed white often combines white legs, a broad white face and blue eyes. Several DNA variants can produce it, so a useful result names the particular variant rather than just saying splash.
Dominant white and white spotting
Dominant white is the historical name for a group of KIT variants. Some give small white markings and others an almost white coat from birth; their health implications must be considered individually.
Read the full explanation: Dominant white and white spotting
Leopard complex and PATN1
Leopard complex can give spots, a white blanket or progressive mixing of white hairs. LP helps produce these features; PATN1 changes their extent. Two LP copies also cause impaired vision in dim light.
Classic roan
Classic roan mixes white hairs through the body while leaving the head and lower legs darker. DNA tests often use nearby markers rather than the causal variant itself. Their reliability depends on which markers are tested and whether they have been validated for the horse’s genetic background.
Rabicano
Rabicano describes white hairs concentrated especially around the flanks and tailhead. Researchers have studied a candidate DNA region, but the cause and a universal model of inheritance remain unconfirmed.
Pangaré or mealy
Pangaré lightens the muzzle, belly and other local areas without producing the unpigmented white patches seen in spotting patterns. Researchers have proposed candidate DNA regions, but no single molecular explanation or diagnostic test applies to all horses.
Flaxen mane and tail
Flaxen describes a chestnut horse whose mane and tail are much paler than its body. The appearance is familiar, but a single causal DNA variant and universal inheritance rule have not been established.
Sooty or shaded
Sooty describes dark hairs or shading over a coat, often most visible along the upper body. Studies of bay shade offer leads, but they do not yet explain every horse given this description.
Brindle and Brindle 1
Brindle means a striped appearance, which can have different causes. Brindle 1 is one identified DNA variant affecting hair texture; its inheritance depends on the X chromosome and on the horse's sex.
Pigment
A pigment is a substance that gives color. Horse hair mainly contains two pigment families: black-to-brown eumelanin and red-to-yellow pheomelanin. Their amount and distribution help determine the coat’s appearance.
Eumelanin
Eumelanin is the black-to-brown pigment in hair. In a bay horse, it colors areas including the mane, tail and lower legs. Variants in several genes can alter its production, distribution or appearance.
Pheomelanin
Pheomelanin is the red-to-yellow pigment in hair. It produces the base color of a chestnut horse. Some dilutions lighten this pigment and can greatly change how that base looks.
Dilution
A dilution is an inherited change that lightens the coat’s pigment color. Its effect depends on the variant, the number of copies and the base color. A pale coat alone does not identify the dilution responsible.
White pattern
A white pattern describes the arrangement of white areas in the coat. Different genetic causes can produce similar-looking patches. Their shape does not always identify the variant, and several patterns can occur in the same horse.
Melanocyte
A melanocyte is a cell that makes pigments called melanins. These pigments contribute to skin and hair color. Differences in how these cells develop, where they are present and how they work help explain coat variation.
Dorsal stripe
A dorsal stripe is a line of darker hair along the back, running from the mane toward the tail. It can accompany Dun dilution, but a dark stripe alone does not prove that the Dun variant is present.
Primitive markings
Primitive markings are darker areas such as a dorsal stripe or bars across the legs. They are often seen with Dun. Some can also occur without the body lightening associated with that dilution.
Chestnut
A chestnut horse has red hair ranging from pale copper to very dark brown. Its mane and tail are red or lighter. Unlike a bay horse, a chestnut has no naturally black mane, tail or lower legs.
Bay
A bay horse has brown to reddish-brown hair on its trunk and neck, with a black mane, tail and lower legs. Some bays are light brown; others are very dark, almost black.
Black
A black horse has black hair on its trunk, neck, mane and tail. Sunlight can fade some of the coat to brown. Fading does not turn the horse into a bay: new hair grows back black.
Palomino
A palomino horse has golden hair on its trunk and neck, with a cream or almost white mane and tail. Shades range from pale yellow to deep gold. Some palominos have darker hairs or darker manes.
Buckskin
A buckskin horse has yellow to golden hair on its trunk and neck. Its mane, tail and lower legs usually remain black. Golden hair combined with black points distinguishes buckskin from palomino.
Smoky black
A smoky black horse may look black or very dark brown. It nevertheless carries one Cream copy, the same variant that makes a chestnut horse palomino. On a black horse, that Cream copy can be almost invisible.
Cremello
A cremello horse has very pale cream hair on its trunk and neck, an almost white mane and tail, pink skin and usually blue eyes. A slight cream tint remains even when the horse looks white from a distance.
Perlino
A perlino horse has very pale cream hair on its trunk and neck. Its mane, tail and lower legs may retain a stronger beige or reddish tint. Skin is pink and eyes are usually blue.
Smoky cream
A smoky cream horse has very pale cream hair, pink skin and usually blue eyes. Its mane and tail may retain a slightly stronger tint. The horse’s original black color is strongly lightened.
Bay dun
A bay dun horse has sandy to ochre hair on its trunk and neck, with darker mane, tail and lower legs. A dark dorsal stripe follows the spine, and bars may appear on the legs.
Red dun
A red dun horse has peach to reddish-sand hair on its trunk and neck. Its dorsal stripe and any leg bars are red or reddish brown. Those markings are not black because the horse’s base color is chestnut.
Grullo (black dun)
A grullo horse has mouse-gray or slate-colored hair on its trunk and neck, with a black mane and tail. Its dorsal stripe is dark and its legs may be barred. The grayish body hairs are still pigmented hairs.
Gold champagne
A gold champagne horse has golden hair on its trunk and neck, often with a lighter mane and tail. Pinkish skin develops dark freckles. A foal’s initially pale eyes generally become amber.
Amber champagne
An amber champagne horse has golden to tan hair on its trunk and neck. Its mane, tail and lower legs are brown rather than black. Skin develops dark freckles and eyes are often amber.
Classic champagne
A classic champagne horse has taupe to chocolate-brown hair on its trunk and neck, sometimes with darker mane and tail. Pinkish skin becomes freckled and eyes often turn amber.
Silver bay
A silver bay horse retains reddish to brown hair on its trunk and neck, with a silver or very pale mane and tail and lightened lower legs. The contrast between reddish hair and pale mane can be striking.
Silver black
A silver black horse has chocolate to brown hair on its trunk and neck, with a silver or almost white mane and tail. Rounded lighter or darker markings, called dapples, may appear in the coat.
Mushroom (chestnut)
A chestnut mushroom pony has grayish beige, sepia or muted brown hair on its trunk and neck, often with a lighter mane and tail. The usual chestnut red becomes a softer shade that can approach taupe.
History and domestication
Riding a la jineta
A riding practice described in Iberian equestrian history and connected with exchanges involving North Africa. It is associated with shorter stirrups and mobility of horse and rider. Historical texts distinguish it from riding a la brida; these expressions describe practices, rather than horse breeds.
Riding a la brida
A historical riding practice distinguished in Iberian texts from riding a la jineta, notably in accounts of heavy cavalry and its equipment. The expression describes a practice within its historical setting, rather than defining a breed or every use within a community.
Albeitería
A historical Spanish name for equine medicine. Practitioners and treatises addressed matters such as disease, care and horse maintenance. These texts reveal the knowledge of their period; their treatments are not present-day veterinary advice.
Palaeolithic
A long period of prehistory when people made tools from chipped stone and lived on wild resources. Horses depicted in Palaeolithic art predate known domestic breeding. The date of a painting tells us about a representation, rather than how many horses lived in the area.
Zooarchaeology
The study of animal remains found at archaeological sites, particularly bones and teeth. It helps identify species, animal ages, diet and some traces of work or butchery. Remains from a site document animals recovered in that context, rather than providing a census of an entire region.
Animal traction
Using an animal’s strength to pull a load, vehicle or tool. A horse pulling a carriage and a mule pulling a farm implement both provide animal traction. Carrying a load on the back is instead described as pack transport.
Horse-drawn omnibus
A public passenger vehicle pulled by horses along a set route. Horse-drawn omnibuses carried people around cities before motor buses took their place.
Domestication
Domestication is a process across generations in which relationships with humans change how an animal population lives and reproduces. It differs from taming one individual. Evidence of horse keeping alone does not identify the ancestors of all modern domestic horses.
Ancient DNA
Ancient DNA is genetic material recovered from remains of the past, such as bones or teeth. Comparing it with other samples helps researchers study relationships between populations and changes over time. Preservation limits the information available.
Feral population
Animals living freely whose ancestors were domesticated and then escaped or were released. Mustangs are an example. Feral describes that history of domestication and subsequent free living; it is not the name of a single breed.
Warmblood
A term covering several riding and sport-horse populations, particularly European ones such as the Dutch Warmblood and Hanoverian. It does not mean one single breed or a different blood temperature. Each studbook sets its own breeding and registration requirements.
Glossary sources
These sources explain the language of genetics, breeding and horse history. For conditions and coat colors, the detailed articles present the research and laboratory resources behind the explanations.
- RAE — definition of riding a la jineta
- Morales Muñiz — medieval riding and equine care, 2010
- Lira Garrido et al. — ancient Iberian horse genomes, 2025
- MAPA — equid identification and traceability
- RFHE — introduction to doma vaquera
- IFCE — history and role of the national studs
- City of Paris — omnibus and bus history
- UNESCO — tbourida
- Université Paris Descartes — horse–donkey hybrids
- FAO — World Programme for the Census of Agriculture
- IFCE — studbook definition and organisation
- IFCE — breed programmes and registration rules
- IFCE — assessing a horse’s conformation and movement
- UC Davis — genetics glossary
- FFE — equestrian disciplines
- APSL — Lusitano studbook regulations
- ANCCE — PRE studbook documents
- ABPSL — Brazilian registro genealógico and Stud Book
- NHGRI — Genetics glossary
- UC Davis VGL — Equine coat color genetics
- IFCE — The inbreeding coefficient
- UC Davis — Melanoma in horses
- Librado et al. (2024) — Ancient DNA and the spread of horses
- MFTHBA — Missouri Fox Trotter gaits
- WHOA — Tennessee Walking Horse gaits
- USTA — trotting, pacing and harness racing
- BLM — origins of free-roaming horses
- Scottish Government — hands, inches and centimetres
- Oklahoma State University — warmbloods and the KWPN