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Roan
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(True) Roan
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A horse that is a true roan will have white hairs scattered throughout its coat on its body, but the head, legs, mane and tail will remain the base color of the horse.
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Generally, the dark to white ratio is about 50/50 and the mixture tends to be quite uniform overall. The horse often appears from a distance to be a light color, and it's only apparent
upon closer inspection that the light appearance is caused by a mixture of white and dark individual hairs.
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R : True roan is caused by the
gene abbreviated R , which is dominant; a horse must *be* a roan in order to have a roan offspring, and a roan can never come from two non-roan parents.
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r : the absence of the
roan gene, which is recessive, is represented by the lower-case
r.
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Dominant and recessive genes are explained in the
Beginning Genetics section.
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The R gene has long been
believed to be lethal in the homozygous
(RR) state, with those embryos being resorbed very
early in the pregnancy (usually before the owner knew the mare had
conceived).
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There is a test for roan, which does show homozygosity in some
living, adult horses, but since the Hancock bred horses were used for
the research leading up to this test, and those horses have many
"frosty" roaned individuals (including those with true roan and
frosty
also), some color researchers believe that this test
may actually be detecting "frosty", a different form of "roaning" (see
frosty,
currently on the leopard complex page.)
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Roan is not progressive -- it doesn't increase over the
years, as gray does. But it often varies with the season; usually
lighter in winter and darker in summer; and can also vary from year to
year.
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Roan horses often have dark, rounded spots within the roaned areas,
commonly called "corn spots".
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Roan may be "e" linked, that is, inherited together with the e, or
red, gene.
Pictures coming, etc. etc. |
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