Iberian horses have a medley of unusual colors some breed aficionados may be surprised to see! For the most part, gray is the predominant phenotype (outward appearance) found in both Spanish and Portuguese horses. Lusitanos are famous for having a wider variety of coloration, but as it turns out, despite the culling, pure Spanish horses have in fact retained the same unusual colorations found in their Portuguese relatives. As the studbooks were split less than 50 years ago and many of these colors historically existed in Spain without any help from Lusitanos, it is not unremarkable to believe that a number of unusual colors have “hidden” behind gray or even black for the last few decades.
Spain has recently lifted the rule that precluded horses of any color other than gray, black and bay from entering the studbook. Chestnut, cream, pearl, silver dapple, classic roan (Lusitanos only), sabino, and rabicano have all reappeared, and have been confirmed with DNA testing. They somehow managed to survive, and are now allowed in the studbook again. Leopard spotting, which actually originated on the Iberian peninsula and was confirmed to exist there as far back as 30,000 years ago, and tobiano coat patterns are thought to been permanently eradicated from the gene pool.
We are now seeing a worldwide “color fad” in which unusually colored horses are highly sought after and are being bred for specifically, sometimes to the detriment of the horses’ type and quality. However, as time goes on, more and more quality horses of unusual colors are making their way into more and more stables worldwide. Here is a guide to help you sort through the color jargon.
Homozygous – Two copies of the same gene. Will pass to 100% of offspring.
Heterozgous – One copy of the same gene. Will pass to 50% of offspring.
Phenotype – The outward appearance of an animal
Genotype – The genetics of an animal, which may be hidden beneath a phenotype
Dominant: A gene which will express itself when present in only one copy
Recessive: A gene which will hide under the animal’s phenotype, unless present in two copies
Double Dilute: Two copies of the Cream gene
The gray gene is dominant, which means it will be expressed whether or not there are two copies. Gray can appear on any “base” coat color, and will eventually turn the horse completely white. Gray horses may be prone to melanomas and should be carefully monitored for unusual growths. Gray horses are born with their base coat color, and will lighten in a variety of different patterns and time frames. Some horses take decades to gray, while others may be gray before they turn a year old. Homozygosity may play a role in the rate of graying.
Coat color tests describe the gray gene with a capital “G” when present, and a lowercase “g” when absent.
A homozygous gray horse will be designated as “GG”. A heterozygous horse will be designated as “Gg”, and a non graying horse will be designated as “gg”
There is a gray suppression gene recently discovered and confirmed to exist in Iberian horses. This gene may cause a gray horse to appear to be rabicano, or it may prevent the horse from graying altogether, but the horse can still have gray offspring. More research is pending.
Black, and Red Factor
(Black and Chestnut)
The presence or absence of the dominant Extension gene is responsible for red/black factor coats. If the Extension gene is present (one or two copies) the horse will be black. If absent, the horse will be chestnut. Chestnut and Black are the two “base” colors associated with horses, and a number of modifiers and dilutions will alter the horse’s phenotype and change its coat color.
Black based coats include: bay, buckskin, smoky black, smoky cream, and perlino. These horses will always carry one or more copies of Extension.
Red based coats include: chestnut, palomino, and cremello. These horses never carry Extension.
In a coat color test, Extension is designated as the letter “E”. A horse homozygous for the Extension gene will be described as “EE”. A black horse heterozygous for Extension will be described as “Ee”. A chestnut horse without Extension will appear on a test as “ee”.
the Agouti (ah-goo-tee) gene is named for a large South American rodent of the same color. It is the dominant gene which causes a horse to be bay. A bay coat is the result of one or two copies of Agouti modifying a black coat. A Chestnut horse can carry agouti without expressing it, since Agouti only affects black pigment.
In a coat color test, Agouti is designated as the letter “A”
A homozygous horse will be described as “AA”. Heterozygous horses will be designated as “Aa” and horses who do not carry Agouti will be described as “aa”.
Cream is an incomplete dominant gene, meaning that while it is expressed when heterozygous, two copies will magnify the effect on the base coat.
Horses heterozygous for cream will be Buckskin (on bay), Palomino (on chestnut) or Smokey Black (hidden behind a black phenotype).
Homozygous horses will be Perlino (on bay), Cremello (on chestnut) or Smokey Cream (on black).
On a coat color test, Cream is described as “Cr”. A homozygous horse will be described as “Cr Cr” and a heterozygous horse will be “Cr cr”, and a horse lacking cream will test as “cr cr”. A horse homozygous for cream is described as a “double dilute”.
Pearl is a newly discovered recessive gene which was first identified in the bay Andalusian stallion, Bravio. Pearl is recessive, so it “hides” beneath a horse’s phenotype when heterozygous. When homozygous, however, Pearl will make a horse with any base color appear to be a double dilute, and has no doubt been the source of a great deal of hand wringing and double checking of breeding documents.
Interestingly, Pearl occupies the same location on a horse’s chromosome as Cream. This means that a horse cannot carry more than one copy of Cream if it also has Pearl, and visa versa. Even more interestingly, these two genes interact. A horse that has both Cream and Pearl will resemble a double dilute.
Pearl horses can be visually identified by green eyes, and a purplish hue to the skin around the muzzle and genitals. Subtle mottling of the purplish skin may also be present. There are several horses carrying the Pearl gene in the US, but they are still quite uncommon.
Coat color tests designate Pearl as “Pr”. Homozygous appears as “PrPr”, heterozygotes will test as “Prpr” and horses lacking Pearl will test as “prpr”
Silver dapple is an extraordinarily rare dilution, so far only confirmed to exist in PRE horses in Germany. Because it is so rare, it is often misidentified as flaxen chestnut, and will likely appear more frequently now that it is more widely tested for. In fact, Spain is now testing for Silver as part of its routine coat color testing. Silver Dapple only affects black pigments. A black horse will have a black coat, with a lightened mane and tail, and a bay horse will have a brown coat with a lightened mane and tail. Dark points around the ears, muzzle, and knees will still be present. Chestnut horses are not thought to be affected. Silver Dapple causes blindness when homozygous, and is likely the reason for the rarity of the color in all breeds.
American horses with Silver Dapple include Morgan horses, Quarter horses, and Rocky Mountain horses, all breeds with roots in Spain. “Silver Dapple” is sometimes confused with dapple gray horses who have been informally described as “silver” and “dappled”, but this fanciful description has nothing to do with the Silver Dapple dilution,￼just as gray horses who are described as ‘white” have nothing to do with Dominant White (not found in Iberians). Silver dapple, in combination with gray, will cause the horse to turn gray far more rapidly than is normal, often leaving a horse completely white before it is even weaned.
Silver Dapple is described by coat color tests as “Z”. Homozygous horses are “ZZ”, heterozygous horses are “Zz” and horses lacking in Silver are “zz”.
Classic Roan is a dominant gene, and has been confirmed in Lusitano horses in The United States. Classic roan is extraordinarily rare in Iberians. It can only travel in the absence of the Extension (black) gene, so all horses carrying Classic Roan will be either heterozygous for Extension, or lacking it altogether. Anecdotal evidence suggests that Classic Roan will cause a gray horse to turn gray faster.
Sabino describes a complicated group of genes, only one of which is testable. Sabino causes white markings which may include socks and stockings, as well as belly spots and even larger irregular white pinto markings. Roan patterning, especially around the belly and flanks is common with sabino. Only Sabino -1 can be tested for.
Rabicano created limited roaning, often around the belly and flanks of the horse. Telltale white hairs around the base of the tail are often a givaway for Rabicano. Belly patches and other white markings may accompany Rabicano.
Dun does not exist in Iberian horses, and dubious examples have never been confirmed with color testing at the time of this publication. The leg barring and dorsal stripes found on many Iberian horses is not Dun, nor does it test as anything in particular. These markings are in fact ordinary countershading, and not dun. While this type of countershading may turn out to be unique to Iberian horses, it is certainly not dun, it does not test, and it doesn’t modify coat colors.
A horse which is turning gray one white hair at a time is very common, and it is not Roan, rabicano, or sabino. It is Gray.
Champagne does not exist in Iberian horses.