Question 1

How do you predict a foal's color?

Accepted Answer

Foal color is predicted using genetic inheritance patterns from both parents. The two primary genes determining base color are Extension (E/e) and Agouti (A/a). Each parent passes one copy of each gene to offspring. Extension determines if the horse produces black (E) or red (e) pigment, while Agouti (A) restricts black to points, creating bay. By calculating all possible combinations, you can determine probabilities for bay, black, and chestnut foals.

Question 2

What is the Extension gene in horses?

Accepted Answer

The Extension gene (E/e) controls whether a horse produces black or red pigment. E (Extension) is dominant and produces black-based colors (bay or black). e (no extension) is recessive - horses with ee genotype are always chestnut/red, regardless of other genes. A horse needs only one E allele (EE or Ee) to be black-based. The Extension gene is the most fundamental color gene in horse genetics.

Question 3

What is the Agouti gene in horses?

Accepted Answer

The Agouti gene (A/a) restricts black pigment to the horse's points (mane, tail, ear tips, and lower legs), creating bay coloring. It only affects black-based horses (E_) - it has no visible effect on chestnuts (ee). A is dominant, so horses with AA or Aa genotypes will be bay if they're black-based. Horses with aa genotype will be solid black if black-based (E_).

Question 4

What are the three base horse colors?

Accepted Answer

The three base horse colors are Bay (E_ A_), Black (E_ aa), and Chestnut (ee __). Bay has a brown/reddish body with black points. Black is solid black throughout. Chestnut is reddish-brown with no black pigment. All other horse colors are modifications of these three bases through dilution genes (Cream, Dun, Champagne, Silver), pattern genes (Tobiano, Overo, Appaloosa, Roan), or white markings.

Question 5

Can two bay horses have a chestnut foal?

Accepted Answer

Yes, if both bay parents are heterozygous for Extension (Ee). Bay horses have genotype E_ A_, meaning they have at least one E allele and one A allele. If both parents are Ee, each has a 50% chance of passing e to offspring. When both pass e, the foal is ee (chestnut), with 25% probability. Two EE bay horses cannot produce chestnut foals. Genetic testing can determine if bay horses carry the e allele.

Question 6

Can two chestnut horses have a bay or black foal?

Accepted Answer

No, two chestnut horses can only produce chestnut foals. Chestnut horses have ee genotype, meaning they have no E allele to pass on. Since they can only pass e alleles, all offspring will be ee (chestnut). This is why chestnut 'breeds true' - chestnuts always pass their base red color. However, foals may vary in shade or have dilutions (palomino, cremello) if parents carry dilution genes.

Question 7

What is horse color genetics testing?

Accepted Answer

Horse color genetics testing analyzes DNA to determine exact genotypes for color genes. Tests are available for Extension, Agouti, Cream, Dun, Champagne, Silver, Tobiano, Frame Overo, Leopard Complex, and other genes. Testing costs $25-75 per gene. Labs include UC Davis VGL, Animal Genetics, and Etalon Diagnostics. Knowing exact genotypes helps breeders predict foal colors with certainty and avoid producing unwanted colors or lethal combinations like Frame Overo.

Question 8

How accurate is a horse color calculator?

Accepted Answer

Horse color calculators are 100% accurate for base colors (bay, black, chestnut) IF you know the exact parent genotypes. However, most calculators only predict base colors, not dilutions or patterns. Without genetic testing, you must estimate parent genotypes from phenotype and offspring history, reducing accuracy. For complete accuracy including all color possibilities, genetic testing is recommended. Calculators are educational tools and helpful for understanding inheritance patterns.

Question 9

What other genes affect horse color besides Extension and Agouti?

Accepted Answer

Many genes affect horse color: Cream (dilutes red/black to palomino/buckskin/cremello), Dun (primitive markings, lighter body), Champagne (dilutes all pigment), Silver (dilutes black), Gray (progressive whitening), Roan (white hairs throughout coat), Tobiano/Overo/Sabino (white patterns), Appaloosa/Leopard Complex (spotted patterns), and Dominant White. Each follows Mendelian inheritance with different dominance patterns and interactions.

Question 10

What is the rarest horse color?

Accepted Answer

The rarest horse colors are: True White (Dominant White homozygous), Brindle (vertical striping, cause unknown), Mushroom (champagne + cream on chestnut), and certain dilution combinations. White and Cremello/Perlino are rare but not rarest. Black is less common than bay but not rare. Color rarity varies by breed - some colors are common in certain breeds but rare overall. Rarity doesn't indicate value - breed quality and conformation matter most.

Horse Color Calculator - Foal Color Genetics & Breeding Predictor

Sire (Father) Genetics

Dam (Mother) Genetics

Predicted Foal Colors

Bay

Chestnut

Black

Base Horse Colors & Genetics

Quick Example Result

How the Horse Color Calculator Works

Horse Color Genetics Rules

Understanding Horse Color Inheritance

Sources & References

Horse Color Calculator Examples

Parent Genotypes:

Possible Outcomes:

Chestnut × Chestnut

Black × Chestnut

Frequently Asked Questions

Found This Calculator Helpful?

Related Calculators