Mushroom  -  a Newly Recognised Dilution
For important updates see Kellas Chiffon 2nd pony on right in photo below & page 3
Clibberswick Hammerite  page 4
Smevallens Lotus  2nd pony on page 6
 


left - right: Barclay Arms Wilma (page 2), Kellas Trinket (page 3), Kellas Chiffon (page 3), April Girl of Clonyard (page 2)
 

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.  Some of these ponies are a very pale beige, as in a young mushroom, some much darker in colour, as in an older mushroom.
 

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. Similar 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 some examples on the following pages. 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. The true shade seems very difficult to capture in photographs as different light makes the coat appear a different shade & looking at the pony at different angles alters the perceived shade.
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? A number of people have said it is 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. 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. Two of my unrelated mushroom ponies, Clibberswick Hammerite & Kellas Chiffon, were red factor tested at the Swedish University of Agricultural Sciences at Uppsala & the result for both proved they are chestnut base colour.
N.B. Recent tests conducted at the Swedish University of Agricultural Sciences, show that neither Clibberswick Hammerite nor Kellas Chiffon carry the silver gene. Since then, many other mushroom Shetlands have been tested for red & silver.  All have proved to be red but negative for silver.
 
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 lower 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. There are several ponies registered in past UK Shetland Pony Stud-Book Society volumes that may have been mushroom. As far back as 1893, a filly, Unornia II, was born to a black mare, Guddonia II (1226). Unornia was registered as "Brown, whitish mane & tail". She retained this colouring when registered as a mare (reg. no.1313) in 1898. More recently, the Avening Stud had several foals described as "dun" from chestnut parents. Avening Festina (born 1951) was "silver, flaxen mane & tail" from chestnut parents.
 
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 Stud Book. I have no reason to doubt that Trot's 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 as the ponies that have been tested for silver have proved negative. 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. It is important to remember that all the research into mushroom coloured ponies has been done on UK registered Shetland ponies & their descendants only.  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.


Hair samples left to right: 1) Barclay Arms Wilma body, then, 2) Wilma under mane so not faded; 3) light chestnut; 4) dark chestnut; 5) April Girl of Clonyard body and 6) April under mane where it does not fade. When looking at these samples, it must be remembered that one sees only the tips when viewing any pony. For photos of these ponies, see next page, 'Houlland Connection'.
 

Kellas Chiffon
The mushroom colour blends superbly with surrounding dead grass which makes perfect camouflage.
 

EQUINE COLOR GENETICS

Note: A chapter on the mushroom colour, giving more details, is given in Professor Sponenberg's book "Equine Color Genetics", published in February 2009. This book should be obtainable through Amazon.co.uk or other on-line book stores.

Text & photographs on all Mushroom pages are copyright of Beth  Mead unless otherwise stated  

 

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