Predict foal coat colour across seven loci, enumerating the genotypes each parent's coat is consistent with instead of assuming one, and naming what a test would settle.
Change the inputs that matter to your decision. Optional assumptions stay collapsed until you need them.
A coat narrows the genotype but rarely settles it. The result says which loci stay open.
Bay over Chestnut / sorrel gives 3 possible colours, most likely bay at 65.6%.
A coat does not determine a genotype. Where a parent's genotype is open — listed below — each possibility is taken as equally likely, which is a stated assumption rather than a fact about these horses. A test on the open loci would replace the assumption with an answer, and can change these figures substantially.
| Bay | 65.6% |
|---|---|
| Chestnut | 25.0% |
| Black | 9.4% |
| Unresolved — Extension | sire could be Ee or EEA E test would settle this. |
| Unresolved — Agouti | sire could be Aa or AA; dam could be aa or Aa or AAA A test would settle this. |
| Unresolved — Silver — not visible | The dam's coat cannot show silver, so it is taken as absent.The allele is rare, but a carrier would pass it undetected. A Z test is the only way to rule it out. |
Extension, agouti, cream, dun, champagne, silver, and grey are modelled. Roan, the white spotting patterns — tobiano, overo, sabino, splash — pearl, mushroom, flaxen, and sooty are not, and any of them can change what a foal looks like without changing the colours above.
Practical notes about the inputs, assumptions, and result.
Because a coat does not determine a genotype. A bay horse may carry two copies of E or one, and one copy of A or two — four genotypes producing an identical animal. A chestnut's agouti is completely unreadable, because agouti only shows on a horse that can make black pigment. Any tool that returns exact percentages from two coats has quietly picked one genotype for you, and picking wrong changes the answer entirely.
No. Chestnut is homozygous recessive at extension, so both parents can only pass e, and every foal is a chestnut. This is one of the few crosses where the coats alone give a certain answer, and the tool reports it as exact rather than as a probability.
Because it is dominant and progressive. A grey foal is born its base colour — bay, chestnut, black, whatever the other loci give — and lightens over several years until it is grey or white. The colour at birth is not the colour it keeps. Where grey appears in the results, the note names what the foal would be born, because that is what you will see first.
Silver dilutes black pigment, lightening the mane and tail and often the body. A chestnut has no black pigment for it to act on, so a chestnut can carry silver and pass it to a foal with nothing visible to warn you. That is why silver is left open for chestnut parents here rather than assumed absent.
The result lists every locus your parents' coats leave open, and each is testable. Extension and agouti are the usual starting point since they set the base colour. If a dilution appears in either parent's pedigree, test for it too — cream, dun, champagne, and silver are all single tests. Testing turns a probability into an answer.
Roan, the white spotting patterns — tobiano, overo, sabino, splashed white — pearl, mushroom, flaxen, and sooty. Any of these can change what a foal looks like without changing the base colours predicted above. The result states this rather than leaving you to assume the list is complete.
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