PRE Coat Colours & Their Genetic Inheritance

Equine Coat Colour Genetics and the PRE
After 32 years of trying to eliminate every coat colour except grey, bay and black from the PRE studbook, a new law was passed on the 23rd December 2002 by the Spanish legislator (Ministry of Agriculture) which contained a clause referring to the Purebred Spanish Horse’s coat colours. This clause says: “The grey and the bay colours are dominant, other colours are accepted”.  With these few words, not only is the chestnut colour officially re-admitted after 32 years of prohibition, but also any other colour is now allowed. Hence, in principle, colour will no longer be a racial criterion, or determining factor for the admission of horses into the PRE Stud Book as approved for breeding.

This Group of pages are organised by the Coat Colours we can see (phenotypes) and the Coat Colour Genes that cause the visible colours (genotypes). There are also a number of Coat Colours in PRE horses that do not yet have any genes associated with them, and so we can only speculate about what may cause them and how they may be inherited. There are links to pdf versions of the published genetic papers on some off the Coat Colour genes.
It is strongly recommended that you go to ‘A Brief Introduction to Chromosomes,Genes & Coat Colour‘ and read this FIRST if you don’t have much idea about Genetics. It should help you understand the individual pages on the various coat colours and how they are inherited in horses.

COLOURS IN THE PRE HORSE  – alphabetical order with the Spanish equivalent afterwards in (), and the main Gene Locus/s that influence the colour.
Bay (Castaña/o)  –  Agouti Locus & Extension Locus
Black (Negra/o)  –  Agouti Locus & Extension Locus
Buckskin (Baya/o) – Cream Locus
Chestnut (Alazan)Extension Locus
Chestnut-Dun (PRE-variant) – Extension Locus / Dun Locus
Cream-Pearl (Perlina/o) – Cream Locus / Pearl Locus
Cremello (Cremela/o)  – Cream Locus
Dun (PRE-variant)  – Dun Locus, Agouti Locus & Extension Locus
Grey (Torda/o)     – Grey Locus
Grullo (PRE-variant) – Dun Locus, Agouti Locus & Extension Locus
Pearl Homozygous (Isabela) – Pearl Locus
Perlino (Perla)         – Cream Locus
Seal Brown              – Agouti Locus & Extension Locus
Smokey-Black (Negra Ceniza/o) – Cream Locus
Smokey-Cream (Negra Crema)  – Cream Locus
Smokey-Grullo        – Cream Locus/Dun Locus, Agouti Locus & Extension Locus

by Mary McBryde BScHons

Today the PRE studbook shows a far large number of ‘Grey’ horses (horse with progressive loss of colour – see accompanying genetics article) than horses of  without the Grey gene which keep their birth colouration for life, but this was not always the case.
Our breed is a very ancient one and old paintings from many centuries ago show the Andalusian in a huge range of colours, including true roans, piebalds, skewbalds, spotted ones and all shades of diluted colours. Indeed it is thought by Colour genetics researchers that the spotting genes for the Apaloosa and all other spotted breeds around the world care traceable back to Spanish horse ancestry.
Around 1880 the PRE (Andalusian) in Spain became genetically isolated with a closed studbook admitting no horses that were not of pure breeding. Crossing with its close relative, the Lusitano, was forbidden and any products from such a breeding were registered as Lusitanos until the restructuring of the Portuguese Studbook in 1990s when outcrossing the Lusitano was forbidden within Portugal and that too became a closed studbook.
The early bound volumes of the Spanish studbooks show the PRE to be a breed that still had a wide variety of coat colours including buckskin/dun, black, chestnut, isabella (variable definitions), perla, bay, etc,  but no longer the spotted and white patched colours. Horses that had Progressive Greying gene were very much the minority.

Note: for those of you who research colours using the ANCCE-LGPR database on-line or through their software programme.. When the information in the bound volumes of the Studbooks was transferred to the computer database,  the people doing so did NOT bother to transfer most of the early colour and breeder data. Where the LGPRE programme says ‘Not known’ , the information is usually available in the old bound volumes, and often with details about white socks and facial markings, plus how much the horse cost and what they thought of it !   The BAPSH Ltd Registry office has a complete set of the old bound volumes containing all the data back to 1880s.

After the 1880s the PRE went through several severe genetic ‘bottlenecks’ caused by civil and world wars. Numbers were so low that there was an export ban until 1963. The main breeding stallions to procreate during the second world war were GREY (base coat unknown). It was at this time that the Grey Gene came to dominate the breed until over 75% of PRE carried Progressive Greying.
From the 1880s until 01/01/2007 the PRE studbook has been controlled by the Spanish Ministry of Defence.

a) Between the years 1970 and 2003 the coat colours of Chestnut, Palomino, Blue eyed creams, pintos, white spotted etc, and anything that could be interpereted (or misinterpreted) as these colours was banned by Spanish Law from registration.

b) The Studbook managers of that period intended to make the breed a Grey and Bay breed only. Any other colour was deeply frowned upon and widely different coat colours such as buckskins and blacks were all registered as BAY; the more recent volumes of the Spanish Studbook are absolutely packed with major errors like this, making life a nightmare for anyone trying to track true colours in pedigrees.

c) The Spanish Studbook has always treated the Progressive Greying Gene as an actual COLOUR, ignoring the foal’s basecoat. Therefore, fortunately, they continued to register into the Studbook all the Chestnuts, Duns, Buckskins, Blacks, and other Odd Colours that Greyed out very quickly. As a result these colour genes have been preserved by the very loss of their visible effects in the coat – a bit bizarre – but a miracle today.
NOTE: The Lusitano has never had any restrictions placed upon it with regard to coat colour – all colours have remained acceptable, hence the lovely range of colours they demonstrate still.

d) On January 1st 2003 the Law governing the PRE was changed, and one change was to permit ANY COLOUR to be Registered. Looking back over the last few years of PRE breeding in Spain prior to 2003 it is clear that some Spanish breeders were aware of the fact that the Spanish Government was going to change the Law regarding Coat Colour in the PRE and they started to keep (collect together) all the strange and rare coloured PRE foals which for the previous 30 years had been sold off as unpapered and ‘nonpedigree’ to working homes.

e) A two year amnesty was offered to permit any adult horse of a previously banned color that could prove its parentage by DNA testing, pedigree, and provenance to be registered, and that is the reason that we suddenly had a small but very useful population of rare coloured adult horses arrive into the Studbook.

However the percentage of Grey gene carrying PRE horses is still very high, and many of them are homozygous for Grey (ie. carry a pair of Grey genes and can never produce anything except foals that will lose their colouring). As a result of this high level of homozygosity, trying to extricate the interesting colour genes from the drastic effects of greying without losing quality and type is proving an interesting challenge for breeders. This is compounded by the problem touched on in point  c) above. ie. Identifying the Colour Genes that are being found is very difficult because very often one or more parents of an unusual colour horse are simply listed as GREY and the parent’s birth colour is not known. Sometimes the whole 5 generation pedigree will be Grey !! Alternatively the parents may be solid coloured but wrongly identified. Many Grullos (Black + Dun) are mis-registered as Bay !!
In 2004 the first truly ‘weird & wonderful’ coloured PRE horses were seen at the National Championships in Spain (SICAB). I saw the photos of the one attached (Especial IV) and my initial conclusions were that it was likely to be a Champagne on a Black base coat (a colour recently discovered in some American breeds). Over the following 3 years I saw photos of another 5 PRE horses that seemed to be a similar colour to Especial IV. However research into the Champagne gene was ongoing in the USA and this coat colour mutation was shown to be caused by a dominant gene, so at least one parent had be a Champagne colour (ie have the rare coat colour gene) in order to be able to produce a foal with the Champagne dilution. This meant that the unusual coloured PREs could NOT be Champagne as they were born to parents that did not have their colouring. The huge mystery was cleared up in 2008 when UCDavis announced the discovery of a rare recessive mutation in PREs and Quarter Horses which they called ‘Pearl’.  (More information about Pearl can be found on the dedicated page)

Especial IV, Stallion SICAB 2004, left side whole horse
Since the relaxing of the criteria for PRE coat colours in 2003 the breed has seen a slow but steady increase in the number of horses with previously rare or banned colours. This has been largely driven by the enormous prices the rare coloured horses were able to command, regardless of quality or type. Now in 2016 the quality of the rare colour horses has improved enormously because the increase in numbers has enabled breeders to select for better type and conformation amongst their ‘special colours’. Some colours are becoming relatively numerous and in the UK we actually have more Buckskins than Chestnuts, and prices of buckskins have dropped from 25,000 euros for a yearling 6 years ago to a price similar to any other good PRE youngster.

Palominos and Smokey Blacks are still quite unusual, probably because the Chestnut and Black basecoats are in the minority compared to the PREs with a Bay basecoat. Double cream gene dilutes and double pearl gene dilutes are still very rare and are not easy to breed or buy because relatively few are born in the world each year.

In 2006 a new coat colour mutation occurred spontaneously in the PRE when a bay filly with a white bonnet, brilliant blue eyes, and 4 white stockings was born to two very well bred solid bay parents. The white colour pattern was very similar to the well-known colour pattern ‘Splashed White’. DNA parentage testing confirmed that the filly was truly the daughter of her proposed parents and she was registered as Unica LXXX. To read more about what has happened with this new colour in the last 10 years go to the PRE ‘Splashed White’ page.
Unica LXXX leftside img_935_4

Copyright Mary McBryde 01-06-2016