BASE, SINGLE & DOUBLE DILUTE COAT COLOURS EXPLAINED
Reproduced here with the kind permission of the author Sorrel Lambton (BHSAI . ICES)
Fundamental Genetics
Horse coat colour genetics is an interesting, complicated, and sometimes confusing subject! As more research is carried out we gain a greater understanding as to how, why, and where some of the more unusual coat colours stem from. This is a simplified explanation, which I hope will dispel some of the myths surrounding foals born with unusual coat colours. A horse possesses 32 pairs of chromosomes in each cell, which carries unique information from generation to generation. Both the stallion and the mare’s genetic contribution is equal. When conception takes place genes are not lost or diluted in any way but combined. Horses can be described as either:
HETEROZYGOUS: means the horse possess two forms of a particular gene encoding some inheritable characteristic, which may therefore produce offspring differing from their parents and each other in that characteristic. These horses possess one masking gene (the dominant gene) and one hidden gene (the recessive gene). Because the recessive gene is hidden the horse will appear exactly like a homozygous horse.
HOMOZYGOUS: means the horse has two identical genes at the same place on two corresponding chromosomes. When a homozygous dominant horse is bred to a recessive horse (which by definition is always homozygous), all progeny will look like the homozygous dominant parent, but unlike the parent they will be a carrier (heterozygous) for the recessive gene.
The phenotype (outward coat colour appearance) can be the same with two horses but their genotype (genetic makeup and the information carried by the genes in the cells) can differ. Because the recessives are unknown it can be difficult to determine the outcome of coat colour. Unless we know the birth colour of the sire and dam and understand the reasons why a coat colour occurs the resulting foal colour will be difficult to determine. The only 100% reliable decision is to have a blood test or hair sample test to confirm the genetic makeup of each parent to eliminate guess work and so the ‘chance factor’.
Base colours (C+C+)
There are only two basic coat colours, black (fading and non fading), and red (chestnut). Black, bay, brown and chestnut are called base colours. A base coat colour can only be diluted to a single dilute (C+Ccr) to produce a buckskin (called dun in Ireland) or palomino if a diluting gene is introduced in the absence of other modifying genes. A horse of a base colour does not carry the diluting gene so can never produce a BEC. For example if you bred a BEC mare to a bay or brown stallion the foal will be buckskin. If the same BEC mare is bred to a chestnut the foal will be 100% palomino every time. In general lighter colours are dominant over darker colours. Red (chestnut) is the most recessive colour followed by black. Light bay is dominant over bay, which is dominant over brown, which in turn is dominant over black. All other coat colours are determined by the addition, alteration or absence of these base colours.
Sometimes a horse looks black but in reality is the darkest form of buckskin and so is classified as a single dilute. Unless this horse tests negative for the BEC gene you may have a surprise when breeding!
DILUTE COLOURS
Buckskin and Palomino are called single dilutes (C+Ccr) and each carry the diluting gene that can produce a BEC.
Dun (DD) and Buckskin (C+Ccr) compared
- The term dun used in Ireland is called a buckskin in other countries.
- There is a difference between the genetic makeup of a dun and a buckskin.
- A buckskin is denoted by the symbol C+Ccr and carries a single diluting gene where as a dun is denoted by the symbol DD and can never produce a BEC.
- Dun can be a breed as it can breed pure and will never produce a BEC.
- The dunning gene is dominant and affects all base colours without tending to lighten the legs or front of the face and leaves a darker mask.
- Duns have what are known as primitive markings. Failure to have a well defined dorsal stripe (a stripe along the spine extending into, and matching, the main and tail), and at least one other matching primitive marking like zebra marks on upper legs, or stripes or mottling on other parts of the body means it is not a D-genotype and more likely to be a buckskin (C+Ccr) and a carrier of the single dilute mechanism whichcan produce a BEC.
- Confusingly, some buckskins have a faint dorsal stripe – these are known as linebacked buckskins.
- Buckskins however never have primitive markings.
- Buckskin bred to buckskin or palomino, and some greys can produce a BEC.
- Buckskin is best bred to a base colour and will produce a buckskin, palomino, chestnut, bay, brown or black, depending on which base colour it is bred to – but will never breed a BEC.
- Buckskins bred from a palomino parent will often have some white hair at the base of the tail and sometimes in the main – known as frosting.
- Buckskin can never become a breed as it cannot breed true. It is only a coat colour.
Palomino genotype: C+Ccr
- A palomino like a buckskin is a single dilute. It occurs when a chestnut coat colour is diluted by the action of one diluting gene.
- A palomino should never be bred to another single dilute like buckskin or palomino.
- Palomino bred to grey can produce a BEC unless the grey tests negative for the diluting gene.
- Palomino bred to chestnut produces 50% palomino and 50% chestnut.
- Palomino bred to a base colour will produce similar coat colours like the buckskin but never a BEC.
- Palomino can never become a breed for the same reasons as buckskin. It is only a coat colour.
Double dilutes, pseudo-albino CcrCcr
Blue eyed cream (BEC), cream, psuedo-albino, shiny eyes and cremello are some of the terms used in Ireland, and in other countries, to describe ponies and horses born with pinkish skin (sometimes called pumpkin), off white to cream coloured coats, and pale blue eyes that can appear pink in some light. Other less known terms include perlino, smoky cream or smoky perlino which all look similar except for subtle differences in colour due to the base colour the cream gene is acting on. The genetic mechanism (CcrCcr) which produces these coat colours is called a double dilute and can only occur when both the sire and the dam carry the Ccr gene. Sometimes the BEC has been called an albino which is completely incorrect as albinism does not exist in equines. A true albino has no skin/melanin pigment and can have hearing and sight problems. The term suedo-albino is a form of partial albinism which means they do posses pigment but not as much as other coat colours. A BEC’s eyes, just like a human with blue eyes, will be more light sensitive but no records that I have read so far report blindness. A worldwide survey was carried out in 2000 by the BEC Study Committee (email: mewatson@earthlink.net) via questionnaires to fifty-five connemara owners covering important questions like: light sensitivity, hearing, sight, melanoma, medical problems, rashes, hardiness etc. The results were nearly 100% positive with no one reporting any problems other than some of the BEC’s experiencing nose rash and slight light sensitivity with their pale eyes. Nose rash can occur from sunburn or sensitivity to irritants where any horse with a pink mussel is grazing.
Grey (GG)
Grey horses can be a very grey subject as the colour describes!
- Grey is not a true colour but rather an admixture of light and dark hairs superimposed over the horses entire body, which gradually lighten with age.
- The hair follicle of a grey horse is supposed to be, not only defective, but also not as deep-rooted in the dermis as other horses hair follicles, which is the reason why some people believe, they ‘grey out’, usually by the time they reach 6-8 years of age.
- Greys are more susceptible to melanomas, than other coat colours including BEC’s, of which 95% of cases are benign. However grey horses do suffer from gradual depigmentation usually around the eyes and mussel.
- Grey masks all other coat colours and causes many surprises in the horse-breeding world if the parents are not tested for the diluting gene.
- The birth colour of a foal whom is likely to turn grey should always be recorded as this is an indication of a foals true colour and will help determine how the horse will breed in the future. If for example a foal is born black, chestnut, bay or brown it should not carry the diluting gene and therefore will not breed a BEC foal. If on the other hand a foal is born buckskin it will carry the diluting gene and can breed a BEC foal if bred to another horse caring the dilute gene.
- If a grey shows speckled of fleabitten marks, (red speckles=chestnut; black=black; yellow=dun, buckskin, or palomino) in his coat, this is an indication of the true coat colour/birth coat colour and a guideline for breeders in choosing a correct mate.
- Every grey horse should be tested for the diluting gene CcrCcr to avoid the chance breeding of a BEC.
Conclusion
For the duration of the BEC ban, which spanned almost thirty years, the percentage of buckskins in the connemara breed has approximately halved, and the number of connemaras with grey coat colours has increased from approximately 50% to 70%. Black, chestnut, roan and palomino coat colours have reduced from approximately 10% to 3% since 1960.
Quote from Deidre Feely’s report of 2003:
‘The increase in the proportion of grey ponies in the population over the past few decades has been coupled by a decline in the percentage of dun, brown, black, roan and chestnut ponies. Thus, in recent years, the diversity amoung coat colour in registered Connemara Ponies has diminished’.
I have tried to be as accurate as possible in compiling and writing a simplified insight into how different connemara coat colours are achieved which I hope will give owners and breeders a greater understanding of how, or how not to, breed certain coat colours. There is a place for the BEC mare in breeding the popular buckskin (known as dun in Ireland), if the stallion is chosen wisely!
For anyone interested in exploring the subject further I suggest:
- Horse colour explained by Jeanette Gower
- Wendy Bockman’s website www.doubledilute.com
- Equine Colour genetics by D.P. Sponenberg
- Coat colour genetics by Dr. Ann Bowling
- Coat Colour trends in the Connemara Pony Population in Ireland by Deirdre Feely B. Agr.Sc., Patrick Brophy MVB MRCVS., and Katherine Quinn M. Agr. Sc.
- Characterisation of the Connemara Pony Population in Ireland by Deirdre Feely B. Agr. Sc., Patrick Brophy MVB MRCVS., and Katherine Quinn M. Agr. Sc.
Test to detect the Blue Eyed Gene
It is now possible to have your connemara pony tested in Ireland for the BEC gene through Weatherbys Ireland DNA Laboratory at the Irish Equine Centre, Naas, Co. Kildare. The cost for this service is €30.00 per animal which will be significantly reduced pending negotiations with the Connemara Pony Breeders Society based on future testing of the entire foal crop. The test usually takes between two to three weeks but they will facilitate urgent requests if necessary. Simply ring Laura on 045-875521 or email her on: dnalab@weatherbys.ie with the breeding of your connemara pony.
Copyright Sorrel Lambton 2009
Sorrel, well done,
If only the breeders Society would stop downgrading ponies on the basis of colour, in the case of BEC ponies, very outdated classification rules.
Thanks Jacqui,
I totally agree! Before 1960 BEC’s were often in the show ring both placed and winning. Why the BEC was considered not a real connemara pony, to be excluded for so many years, I will never understand the reasoning behind the committee at that time and the ones that subsequently followed. The BEC ban which continued for too long has created long term adverse results in the connemara gene pool – not to mention the demise of many coat colors in favour of the grey which we all know is the most inclined to develop cancer! It is time for connemara breeders to wake up and become more educated about the origins of the ‘pure bred’ connemara pony. Like many good breeds their origin is a combination of breeds which have been chosen to enhance the native stock – commonly known as the ‘Hobby’. If the society could bring themselves to instigate compulsary testing and disclosure of breeding stallions genetic possibilities then breeders would be better informed as to the possible choices. I must thank Margo Watson for sending me her report on BEC’s from the USA which not only spurned me on to write the article for the greater knowledge of all but has also given me a life long quest for the inclusion and appreciation of the benifits of the BEC! The BEC is the equivalent of a blue eyed human – just a little more light sensitive and nothing more…
Great article, just a small comment though. A BEC does not always produce a palomino when bred to a chestnut. The term BEC covers three colours; Cremello (chestnut base), Perlino (bay base) and Smokey Cream (Black base). A BEC by to buckskin parents will be more likely to be Perlino and therefore on bay base rather than chestnut and therefore it will be likely to produce a buckskin rather than palomino when bred to a chestnut. An example is Skærgårdens Lost Love, by the Perlino mare Fiona II and the chestnut stallion Skærgårdens First Night, she came out buckskin. Pictures of foal, mother and father Can be seen at http://www.skaergaarden.dk, though I don’t think there is an English version of their page.
You’re Right Theresa, and of course many of the foals that are purchased as Dun or Palomino, very often Grey out, only a true dilute that has been tested negative for grey used on a bay or chestnut will guarantee progeny of true Dun or Palomino coat colouration, it is very important that breeders state the birth colour of their foals on their application for Registration, and not what they expect the foals colour to be at maturity.
Theresa,
I have a chestnut mare from a palomino stallion and a dun mare. The buckskin mare obviously had the recessive chestnut gene. The percentage chance of a BEC is I think one in four in that cross and I think the same for a palomino or a buckskin. So, by no means crossing two dilutes will necessarily produce a BEC. The best way of breeding a buckskin is a BEC crossed with bay, and even then if there is chestnut in the backgrounds of both, you can get palomino.
Heather
Heather:
I am sorry if it sounded like I wanted to say that two dilutes will always produce a BEC, I am Danish, so English is only second to my maternal language, mistakes are bound to occur on occasion, as well as stupid autocorrects from my iPad (:
What I mean to say with my comment is that a BEC made from parents where either one or both are buckskin (or dun as it is still called in Connemara societies) are more like to be perlino rather than cremello because chestnut is recessive and is needed in double to make the BEC a cremello, where there is guarantee for a palomino when crossed with a chestnut. I don’t know if it cleared up my point at all, I hope so (:
It was ridiculous to ban BEC’s. I have a BEC filly carrying the grey gene. I was gutted when she tested for grey. If she hadn’t tested positive for the grey gene I would have been 100% guarenteed either a Buckskin or Palomino foal to a Bay or Chestnut sire, finding good BEC Connemara’s isn’t easy, there is one brave stud in the UK concentrating on breeding Buckskins and they breed Buckskin to Buckskin getting the occasional double dilute and the perlino foals are simply gorgeous!! I lovely the cream body and the slightly tangerine/orange mane. I totally regret not having my foal tested before I bought her I so wish I’d got a double dilute without the grey. Try finding a good Bay or Chestnut Connemara sire…very difficult, I wanted to put my filly to a Chestnut Connemara in the hope of a Palomino Connemara part bred around the 15.2 mark and the only ones I can find are a father and son who are 13.2 and 13.3…and that is in the whole of the UK. Connemaras are such versitile talented ponies for both children and smaller adults, it is wicked to deliberately do anything that prevents a variety of colours in a breed, particularly as the faded hair colouring due to the greying gene ends up in the gut and causes cancers. Anyone with a Perlino mare can guarentee a dilute foal if they use a Bay stallion so how ridiculous is it to have people with ‘sought after and acceptable’ common and potentially cancerous grey mares, taking them to a Buckskin sire and crossing their fingers in the hope of a Buckskin foal? As a footnote I bought my filly from Ireland in haste because BEC sportshorse fillies cost thousands due to the guarentees they offer for producing dilutes and guess what, 1/8th of her is Connemara and it’s brought the grey through the generations and threatens my generation of breeding to come…I like greys well enough but I like coloureds, spotted and dilutes more and a grey to those colours makes breeding risky or pointless.
It’s not that I actually think that the BECs should be banned, but I see the point in doing so, since BECs crossed with BECs can only produce more BECs, and it would be less than ideal if you ask me, if the BEC colour became the most common colour for the Connemara pony. True, the greys are potentially cancerous, but the BECs are guaranteed yearly burns from the summer sun if you don’t cover them in sunscreen or keep them indoors. I am all for variety of colours in the Connemara, but too many BECs around and too few Bay or Chestnuts or non-diluted greys around would also make the Connemara less versatile with it’s colours. It was the wrong way to go to ban the BECs but I get why they would feel that they had to, as to not make the colour the primary colour for the Connemara. Noting birth colours of the foals would have seemed a better idea if you ask me, but sometimes the buckskin colour can seem more like brown, so even that wouldn’t guarantee no unexpected colour combinations. It’s sad to think of all the potentially good breeding material that was wasted away with the ban, but since it’s in the past now we can’t do much more than work on getting more colours back into the breed. It has to be done cleverly though, we can’t just breed according to colour without thinking of type and conformation.
An awful lot of breeders In Ireland are misinformed regarding the breeding of true buckskin and Palomino foals, many are under the impression that any cream double dilute to a bay will produce a Buckskin foal, many advertise their creme perlino animals as cremellos, and they have no idea that either perlinos or cremello can still carry grey, until their lovely dun or palomino foal turns grey.
I was looking for a chestnut stallion myself, I would think there should be a few in Ireland, but I will be surprised if they are any classified as Grade 1! If anyone knows of a Grade 1 chestnut in Ireland, please post here!!!
I find it quite embarrassing, to hear the arguements put forward by the Breed Society regarding their rules on colour, and their old fashioned outdated idea that a Connemara pony can be any colour as long as its grey!!!!!! The Dilute Gene on a Black base BUCKSKIN is fine, in fact sought after, but a Dilute gene on a Red base, PALOMINO is’nt, now how nuts is that !!!!! They seem to think that they have moved on and become more forward thinking because very occasionally a BAY gets placed in a show or attains a Grade 1 status at classification.
There is a saying a Good horse or Pony is never a bad colour.
As you stated the developement of unsightly sarcoids (not great if you show) is heightened in greys, with the added risk of them developing into something more sinister.
Why are the Breeders Society considering testing foals for the Dilute Gene?
You can see the birth colour of a foal, so why test?
In New Zealand, thankfully the colour issue is not an issue. We have such a small genepool that fripperies such as colour cannot be afforded.
Here is the website for a sabino liver chestnut Connemara stallion. Brennan is a 5 year old who is out competing in open dressage (against horses), Crossiebeg Brennan from New Zealand Maybe you guys should start looking at importing frozen semen?? And no he is not my pony.
When he was a foal he was described by a visitor from Ireland as being ‘a beautiful colt, a pity he is such a scandalous colour’. We have several ‘scandalous’ chestnuts alive and well and breeding here :)
Hi Sheila, Lovely to hear from you, Sabino !!!!!!! now thats opening another can of worms, lol
Theres no shortage of chestnut colts in Ireland, I think breeders have learned over the years how the powers that be feel about colour within the breed and just don’t bother to bring them out for classification, they just geld them.
Here in Canada I feel lucky our society does not disallow BEC ponies as I adore them! My program is geared towards connemaras of colour that retain the type. It is actually my hope to produce a breeding quality BEC stallion one day.