Appaloosa Horse Coat Genetics

A Guide To Understanding Appaloosa Horse Coat Genetics

Last Updated on February 21, 2022 by Allison Price

People just love a flashy horse. This is one reason the Appaloosa horse has thrived since its inception in North America. While horses of color are revered for their beauty, it was not common to find a flashy foal until recent years. Many breeders were disappointed when their blanketed stallion was not bred to produce a copy of their baby.

Researchers have now discovered some key spots on the Appaloosa horse thanks to DNA mapping.

What it Takes To Be A Good

The Appaloosa horse club (ApHC), recognizes 13 base colors: bay, darkbay/brown and black, as well as grulla, dun palomino and cremello/perlino.

An Appaloosa horse doesn’t have to be spotted in order to be considered one! Two registered Appys can produce a solid foal if they are spotted together. The registry allows this. These horses must be registered with a “N” before their registration number. They also need to have a performance permit to participate in Appaloosa classes. They may also be able to carry the LP gene (more details below). They can be moved to regular registry.

Changing Spots

Some owners might need to change their horse’s registration in order to reflect their horses’ new color. Some foals that are born without white patterning may be able to be changed from the “N” classification to regular. This is because they will develop Appaloosa roaning (or spotting) with age.

Although a leopard cat may not be able change its spots in the wild, these horses can.

Other Markings

Appaloosas may have four additional characteristics, apart from the white patterning.

Mottled skin This is a unique feature of the Appy breed. It gives horses with thin skin and relatively “hairless” areas, such as the muzzle and around the eyes, the sheath, or udder, the appearance of having spots of pink skin in dark areas. As more pigment is lost, this trait can often increase with age.

White Sclera – In most horse breeds you don’t see the sclera, which is the white part around the eyes. This is because in normal pigmented horses, the area around the eyes and iris are brown. Appys have a tendency to see the sclera partially or fully white. This trait does not necessarily mean that there is an LP mutation, as white sclera may also be present on horses with large white facial markings.

Striped hooves Another characteristic that Appys with the LP mutation will have is striped hooves. These are vertical bands of unpigmented and alternately pigmented hoof material. However, this effect is not exclusive to the breed. This effect can also be caused by silver dapple.

Appaloosa Roan is a distinctive pattern of roaning which develops with age and is specifically linked to the LP gene (see further).

Too Many White

Although you might think that “the more splashy the better”, the ApHC has a limit on the number of whites allowed for registration. Ashleigh Brown, representative of the Club, stated that excess white can be defined as:

Continuous leg markings at the top of the forearm, gaskin or stomach; white markings – splotches or paint-like markings behind the throatlatch or behind the ears. A horse with a large white spot on its body (longer/wider that 6 inches) and no other Appaloosa pattern would be considered “excessive white em>

Appaloosa Horse Coat Genetics

Spotting Genes

How do Appaloosas achieve their spots? It all comes down to the genes! The Appaloosa Project consists of an international group of researchers who study the genes that determine how Appys get their coloring. It also explains why a blanketed stallion could have a solid foal. These traits are also related.

After a decade of research, the Appaloosa project discovered the identity of the LP gene and its location in 2013. Sheila Archer, a member the Project’s research team explained to iHeartHorses the LP gene is a mutation in a gene called TRPM1. The LP mutation is a mutation of a TRPM1 gene. It can be found in all mammals but it only exists in horses.

Horses can be homozygous or heterozygous (LP/LP) for the mutation. They also have the option to be homozygous or normal (lp/lp). A foal born from a cross between an LP/LP and lp/lp horses will have one copy of the LP. This gives a 100% chance of having a foal with LP. Other crosses are less likely to succeed. This is why the spotted blanket stallion (if he was an LP/lp), mentioned in the beginning of the article, could produce a solid foal if it was bred to a mare who was either LP/lp (25% or lp/lp) (50%). These examples show that a foal is true solid if it has the normal form gene from both its parents. This article from the Appaloosa Project’s educational site provides more information about the genetics of LP.

However, the LP is not enough to determine an Appy’s coat design. Research has shown that LP is not completely dominant. A horse that has one copy of LP looks very different to one with two copies. White patterning on LP/LP horses has fewer or no spots while LP/lp horses have many dark oval spots. Low white patterns make it difficult to tell if a horse has more than one copy of LP. This is why DNA testing is a great idea!

Once the LP gene has been “On”, it means that the horse carries at most one copy of the LP genetic mutation. It works with a variety of separately inherited modifiers, called pattern genes (PATN), which create beautiful coat patterns visible from birth.

PATN1 is the most important of these, as it has been proven to exist by molecular research. PATN is an essential ingredient that horses with LP need to have extensive white patterning – sufficient to cover most of their bodies in many cases. Although they are yet to be identified, it is likely that there are many small-effect PATN modifiers.

To get a patterned hair, there must be at most one PATN gene that has a significant effect on the LP mutation. A horse that has just inherited PATN genes and not LP will not have the Appaloosa traits or visible coat patterns. It will be a solid animal, but one that could pass on the pattern-causing modifier genes. If the horse has only the LP mutation and no PATN genes, you will still see the Appaloosa characteristics, but not the coat pattern.

Below is a diagram showing the range of coat patterns for horses carrying the LP gene. This diagram is reproduced with permission from Sheila Archer, Appaloosa Project.

One drawback to the LP gene is the fact that horses homozygous (LP/LP), are susceptible to Congenital Stationary Nightblinness.

Archer told iHeartHorses that all horses are affected in the same way. It’s present since birth. “They see nothing below the level at which you can comfortably read a book.” CSNB makes it easy to manage horses. You can find more information about CSNB on the Appaloosa Project educational website (insert link here).

Other Breeds with Spots

There are many other breeds with the LP gene. The Appaloosa Project research has shown that DNA testing has confirmed the presence of the LP gene in these breeds:

  • Knabstrupper
  • Pony of the Americas
  • British Spotted Pony
  • American Miniature Horse
  • Noriker
  • Altai
  • Kyrgyzstan

The LP mutation was found in horses from Europe long ago. It is believed that it existed at least 20,000 years ago. This suggests that all horses with LP can trace their roots back to a common ancestral ancestor.

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