The genetics of equine coat colour
Courtesy of Dr Jenny Cahill
Coat colour has long fascinated horse owners and was one of the first groups of genetic traits to be investigated in horses. For definitions of genetic terms refer to genetics and parentage
There are 4 basic coat colours upon which the myriad of complex colours we observe on horses in the field are built:
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grey
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chestnut
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bay
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black
There are 3 genes which interact to produce these 4 base colours, and there are genetic screening tests available for them.
Once you know the genetic recipe for these 3 genes that make up the base coat colour, it is possible to accurately predict the possible coat colours, and the likelihood of each possible coat colour, of future offspring. Every horse has a pair of alleles for each of the 3 colour genes - one from its dam and one from its sire, and will pass one of the pair on to its offspring. Remember though that the law of averages doesn't always perform as expected!
The 3 genes
1. Grey gene, dominant and overrides the other 3 base colours
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GG or Gg will be a grey horse.
- gg will be a non-grey horse
2. Extension/red gene, determines if pigment in the hair is red or black
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ee, recessive will be a chestnut horse
- EE or Ee will have black pigment (bay or black)
3. Agouti/black gene, acts if black pigment is present and determines whether black is all over or distributed to the points
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So if EE or Ee, black pigment will be present
- and aa, recessive will be a black horse, black all over
- and AA or Aa will be a bay horse, black will be distributed to the points
Some simple rules
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All grey horses must have 1 grey parent
- Mating 2 grey horses can produce non-grey foals
- Mating 2 non-grey horses can never produce grey foals
- Mating 2 chestnuts will always result in chestnut foals
- Mating 2 black horses may produce a chestnut, but never a bay
- Mating 2 bays may result in bay or black or chestnut depending on the genetic recipes of each parent
Which test will give maximum information for your horse?
Test for the marker/gene which is hidden by the base coat colour, so you can then predict possible colours of offspring and choose suitable matings. To have your horse colour tested please contact
Dr Jenny Cahill BVSc PhD
Director
Equine Parentage and Animal Genetic Services Centre
Massey University
Palmerston North
j.i.cahill@massey.ac.nz
More information available on this subject at
http://ivabs.massey.ac.nz/centres/EPAGSC
