The horse coat colours and their heredity in this game are based on real horse colour genetics. Every breed is given a starting percentage for each colour, based on the colours of the breed in real life. For example, the mérens pony is nearly always black, both in the real world and in this game. The same can be said for Friesian horses. But did you know that there some purebred chestnut Friesians in the world? That originally come from black pure bred Friesian parents? This is not impossible, as the chestnut allele is on the same gene as the black allele, but the chestnut allele is recessive. It only shows when two parents with a (possibly hidden) chestnut allele both pass on this allele. Chestnut can, therefore, stay hidden in a breed for a very long time!
Chestnut is not the only colour that can surprise breeders. For example, the silver gene can remain hidden in a complete chestnut family, and the seal brown allele can be masked by bay. There are more of these hidden colours, and sometimes they will appear in the game, just like in real life.
When there are colours in a breed, we always come across the problem of acceptance. Many breeds have colour restrictions. Some of these are fair. A shire horse with a cream gene must have had a non shire horse in its pedigree. But as cream can stay hidden behind a black coat, it can also remain unnoticed for very generations! So if unwanted colours show up in a breed, there is the possibility the horse is not purebred. Therefore, some colours are forbidden.
But some breeds have more impossible rules. A cremello new forest pony is not allowed, but a palomino or a buckskin is (with palomino unwanted for stallions though). However, each of these colours, cremello, palomino and buckskin (and a few others as well!) are caused by one single gene. One cream allele on bay, results in a buckskin. One cream allele on a chestnut results in a palomino. Two cream alleles (for example, when palominos or buckskins are crossed) can result in (for example) a cremello. So, eventually, when palominos and buckskins are accepted in a breed, every once in a while there will be unwanted cremellos (and perlinos and smokey creams). Only when breeding carefully, can these colours be avoided. But why are they unwanted? If palominos can be purebred new forest ponies, why is cremello not wanted? Well, it is commonly believed that horses with a very light coat and/or a light skin, are more vulnerable to the hot sun or different weather conditions. For that reason, some colours are avoided.
Some colours can be lethal.
The two colours in this game that can be lethal, are (dominant) white and frame. A horse with one allele of any of these genes is usually perfectly healthy and not restricted by its colour at all. You will not find adult horses with two of these alleles, however, as they die very early on in their development or shortly after birth. There is no cure.
The best known dangerous colour is frame. The disease is commonly known as the ‘Lethal White Syndrome’. A horse with one frame allele shows a more ‘horizontal’ white pattern across its body. It is healthy and can be very striking and gorgeous. It is mostly known from American paint horses and quarter horses. However, if two horses with one frame allele are bred together, there is a 25% chance that the foal will have two frame alleles. This will result in a white foal that, unfortunately, will die within a few days after birth. The cause is a genetic problem and cannot be healed. A horse with one frame allele also has this problem but will show no symptoms as the other allele is healthy. Only when two alleles come together, does the foal die. Breeders must always pay attention and look for a suitable when breeding with a frame horse.
The other possibly lethal colour is ‘dominant white’. White, white mutations or just dominant white, is very rare and has been recorded as an instant mutation multiple times. It gives rise to white or partially white horses. The Franches-montage horses and the thoroughbreds are some well known breeds with these colours. A horse with one allele of this gene is, for as far as we can tell, completely healthy. It can, therefore, be safely bred to any horse with no white allele at all. But two horses with a White allele could result in miscarriage. Exactly which White alleles are no viable matches is not entirely clear to science. Owners of dominant white horses should be careful when breeding them.
There has been speculation about a third possible lethal colour, called roan. Or more precise, classic roan. At some point in history it was believed roan was homozygous lethal and would result in miscarriage. Nowadays the evidence for this is slim and the colour is completely viable in the game.
At the moment only Frame is lethal when homozygous (meaning, a foal has two alleles of the gene) in the game. So be careful when you’re trying to breed with this colour! Do remember, a horse with just one allele is perfectly healthy and can compete in any sport just like any other! In fact, some people like these colours so much, they would be perfectly happy having a horse with either of these colours!
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