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"Mushroom" - a New
Dilution or Silver Variant? |
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| Some years ago, while looking through some
U.K. Shetland pony stud books, I came across some entries for "mushroom"
coloured foals. Intriguing, but it was not until a couple of years later
that I realised that these entries would become so significant. In the expansion of my Shetland pony herd, I purchased several ponies. Among these were a cream chestnut dun stallion Firth Honeyclover and a cream chestnut dun filly Grimpowood Tammy. The first foal from this pair, initially appeared to be a pale cream chestnut dun filly, but as she coated out, she became much paler in colour, almost resembling a cream foal. The following year, a chestnut mare of my own breeding produced a foal by Honeyclover that appeared palomino. A palomino was impossible, there being no crème gene in the pedigree at all. More of these foals followed over the years and I began to research the colour more thoroughly. Letters, photos & hair samples were sent to acknowledged authorities
all over the world but no-one could tell me what this colour is.
Suggestions were put forward but none seems to fit the results from my own
herd as yet. I
continue to use the word "mushroom" not knowing what alternative to use.
Some of these ponies are a very pale beige, as in a young mushroom, some
much darker in colour, as in an older mushroom. In a letter, Professor
Phillip Sponenberg said he thought mushroom was as good a word as any owing
to mushrooms growing in the dark & he felt completely in the dark on this
colour. |
| So, what are the characteristics of this
colour? The foals I have bred, have been pale at birth, some a pale beige,
some more beige with a greyish or pinkish tint. Some foals have been
registered by other breeders as "grey", "dark chestnut", "roan" or
"cream". The pedigrees & photographs show that the foals are none of
these. Other foals are born pale but turn much darker when adult. I have
researched some of the more common lines where these foals appear & give a
couple of examples. Some lines are chestnut bred for several generations
with no unexpected bays or browns appearing. Other "mushrooms" have
appeared from a black to black mating. All appear sporadically &
in low numbers, a mare perhaps only producing one in a life time. The
summer coat seems to be much the same colour as the winter coat. When the
new coat grows in, it seems to be a little darker than the old coat but
fades very quickly, regardless of the weather. Often, if the pony has a
long thick mane, the coat colour underneath the mane is much darker. The
paler "mushrooms" seem to have paler roots to the hair while the darker
coats have a greyish root to the hair. Some have a very light coloured
mane & tail while others have a lot of dark, near black, & silver hair
through the mane & tail. Some of these ponies have white ticking through
the body coat. An equine vet has looked at the eyes of some of my "mushrooms". So far, they appear to lack pigment at the back of the eye,
so their eyes resemble the eyes of a chocolate labrador dog. Some do have
paler eyes, not blue, but other dilutions such as dun or palomino, can
have paler eyes too. There is no sign of the ASD that exists in some
silvers. None of the "mushrooms" I have, show any redness in the coat. The
coats all have a rather faded look as opposed to the hard, shiny colour of
the normal base colour coat. It is as if someone has removed all the red
from the colour pigment. The darker "mushrooms" sometime show creamy ends
to the long guard hairs & pony's beard. So far, I have found that breeding
mushroom" to "mushroom" has produced "mushroom" coloured foals only.
Hoof colour varies. Some are black, some horn colour & some have varying
degrees of white stripes although there may be no white leg markings. |
| Could it be silver? Silver is said to only
dilute black pigment and not to show if present in chestnuts, but
"mushroom" appears when there is no black pigment present. I have had 2 of
my unrelated "mushroom" ponies, Clibberswick Hammerite & Kellas
Chiffon, red factor tested & the result for both
said they are chestnut base colour. Other "mushrooms" in Sweden that were
red factor tested had
the same answer. When put to black base mares, my "mushroom" stallions
have so far thrown no "mushroom" or silver foals, only black base colour or chestnut
foals. When put to chestnut base mares, most of the foals have been
chestnut, no bays or browns or obvious silvers. My chestnut base mares
have never thrown an unexpected bay, brown or black foal. So "mushrooms" do not seem
to follow the known inheritance pattern of silver. Silver is relatively
common in Miniature Horses but where it is present, it usually occurs in
obvious & spectacular form. If silver is present in the Shetland pony
breed, why is it not seen in similar forms? I would love to see a classic
silver bay Shetland that is registered in the U.K. Shetland pony stud
book. N.B. Recent tests conducted at the Swedish University of Agricultural Sciences at Uppsala, show that neither Clibberswick Hammerite nor Kellas Chiffon carry the silver gene. |
| Could it be champagne? Much has still to
be learned about this dilution but, so far, "mushroom" does not seem to
conform. Neither the eye colour nor the skin colour seem to follow
the acknowledged champagne pattern. The skin colour of my own "mushrooms"
seems to be mainly grey in colour. In some, there is a degree of
mottling around the dock area but nothing really unusual. Could it be pangaré? I have found that pangaré shows as some degree of near white mealiness of the muzzle & belly in the first place. Where the effect is more pronounced, the near white hair on the belly extends up the lower sides, in front of the stifle, behind the elbow, on the legs & around the eyes, but the muzzle always shows some of the mealy effect. In many of these "mushrooms", there is no sign at all of mealiness on the muzzle or belly. |
| Could it be flaxen? Many of these "mushrooms" do have flaxen manes & tails &, in the dun forms, the eel stripe is sometimes missing from the mane & tail, although present as a liver dorsal stripe. However, there are some darker "mushrooms" that have darker manes & tails that have silver hairs through them. They seem to vary greatly. |
| Could it be an, as yet, unrecognised modification of chestnut? The breeding results I have had, although few, do not seem to appear to conform to the accepted silver inheritance pattern but they do conform to chestnut breeding results. It seems to have been present in Shetland ponies for many years but shows more now, perhaps because of closer breeding.. |
| In 1953, W. E. Castle & F. H. Smith wrote a paper on silver dapple in the Shetland pony, where they claimed the gene had mutated in the Shetland pony mare, Trot. Since then, we have learned that the silver gene existed in other breeds, probably long before Trot was born but the colour had not been recognised by science prior to Castle's research. Trot was born in America in 1886 from Jeff & Budge, 2 imported Shetland ponies. At that time, a great many Shetland ponies went from Shetland to America where they were registered in the American Shetland Pony Stud Book according to very strict regulations concerning importation & identification. I have no reason to doubt that her credentials were correct. Trot 31 was registered as "fawn, white mane & tail". Her claim to fame was that she was said to be the origin of spectacularly dappled chestnuts. No mention of spectacular bays with white manes & tails. Was Trot a silver or was she the first recorded "mushroom"? |
| I am not a geneticist & can only report my own findings with regard to study and breeding results. So far, I have no proof of what this colour might be. I find it difficult to call it silver if in the future it may prove to be something else. I do know that breeders should make sure that a foal's registered colour makes it clear that this is not a normal chestnut or crème dilute if great confusion is to be avoided in years to come. If anyone comes across an obvious silver bay with bay body, dark or silver lower legs & near white mane & tail, registered Shetland pony, please do let me know. |
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