Join Date: May 2011
Location: Chino Valley, AZ
To the OP regarding passing on the black gene...
All horses are one of two base colors: red (ee) and black (EE or Ee). Then there are modifiers on top of that. In the case of your mare, she carries the brown form of the agouti gene (AtAt or Atat). There's also the bay form of the agouti gene (AA or Aa) and the wild bay form of the agouti gene (not sure the genetic designation for that one). So, your mare, being brown, would have to be EEAtAt, EEAtat, EeAtAt, or EeAtat. In order to produce a bay foal (if the foal was truly bay and not brown), the sire would have to carry bay agouti (AA or Aa). However, since agouti restricts the expression of black to the hard points of the horse and being a red-based horse, the sire wouldn't have any black to restrict, his agouti status would only be known through testing.
NdAppy and Chiila, that brings a related question to mind. Can a horse carry more than one form of agouti? For example, if the OP's mare is homozygous for brown could she be heterozygous for regular bay as well. Or are they mutually exclusive? I think I know the answer, but I'm still curious.
Posted via Mobile Device