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The podcast discusses the science behind breeding paint horses and the recent breakthroughs in equine genetics. Paint horses are a breed that combines stock-type conformation with colorful coat patterns. They are different from pintos, which are simply a color. Breeders aim to produce foals with visible white on their coats, but genetic testing has made it easier to predict the appearance of foals. The American Paint Horse Association has updated its registration guidelines to include solid horses with the right genetic markers. However, some argue that loosening requirements may compromise the breed's integrity. It is important to research the breed's history and understand the implications of rule changes before forming an opinion. You've probably noticed a paint horse grazing in the field while driving along the road and been mesmerized by their colorful coat patterns, but have you ever wondered how the complex process of genetics plays into the breeding of these beautiful horses? I'm Emily Coggins, and in today's podcast, we're going to dive into the science behind the process of breeding paint horses. Producing foals with chrome can be a lot more complicated than you would think, and recent breakthroughs in the field of equine genetics have become major factors in the industry. First, it's important that you have a basic understanding of what makes a paint horse a paint horse. The American paint horse breed combines stock-type conformation with their signature paint coat patterns, and the American Paint Horse Association is their official breed registry. Paints are often confused with pintos, but they are different. While they both sport flashy coat patterns, paint is a color breed, and pinto is simply a color. Paint horses must have stock-type conformation in addition to their signature coat patterns. Pintos, on the other hand, can have any conformation with the flashy coat markings. That being said, it's important for breeders of paint horses to understand the genetics behind producing foals with color. For generations, breeders have tried to breed mares and stallions with lots of visible white on their coats to ensure that the foals would have a decent amount of chrome as well, but not always with the best results. Sometimes horses with solid coats would be born from two loudly colored paint parents. These horses are eligible for a sub-registry of APHA, known as the Solid Paint Bread Registry, but there are significantly less competition opportunities for solids than regularly registered paints because the focus of APHA has always been to maintain the integrity of the breed, which cannot be done without protecting the unique coloring of the horses because that's their trademark quality. However, recent breakthroughs in genetic testing have changed both the breeder's ability to predict, to a degree, the appearance of the foal, as well as APHA's requirements for regular registry. Today, horses can qualify for regular registry in two ways. The first is coat markings, meaning the amount of white that can be physically seen on a horse's coat. According to the official APHA rulebook, to qualify by coat markings, the horse's white must be at least 2 inches in size, have some underlying unpigmented or pink skin, and be located in the qualifying areas. The qualifying areas are above the center of the knees and or hocks, or behind an imaginary line which runs from the back of the horse's ear to the corner of his mouth. The second is by DNA markers. In 2021, APHA altered their registration guidelines to include solid horses whose genes could allow them to pass white markings along to their offspring. This means that solid horses with the required genetic markers are now included in APHA's regular registry, which was once only available for horses with substantial visible white. Now let's dive into the science behind this in more detail. Each gene in a horse's body has two copies known as alleles. They can have two dominant alleles, which is called being homozygous dominant, two recessive alleles, known as homozygous recessive, or one of each, which is referred to as heterozygous. Recessive alleles create the phenotype or appearance of the horse only if there is no dominant allele present. This applies to all genes, but it is especially important in the context of pink horses. The gene that codes for expression of white in a horse's coat is called W20. Therefore, if a horse is homozygous dominant for the white trait, all of their offspring will have at least some white in their coats. This is because every foal receives one copy of every gene from their dam, or mother, and one copy from their sire, or father. Since each parent has two copies of each gene, it is random which copy will be passed on. However, if one of the parents has two copies of the gene and they are both dominant, then that is all they have to give to the foal, therefore they are guaranteed to pass a dominant copy onto their offspring. However, horses with lots of white in their coats might not necessarily be homozygous dominant for W20. This means that you cannot guarantee what the offspring will look like simply by the outward appearance of the parents. However, in 2019, genetic tests became available which allow owners to determine which alleles their horse has. This enables the breeder to predict the appearance of the foal, to some degree. A link to the simple test is provided on APHA's website. So let's look at an example. Say you have a stallion who is homozygous dominant for the W20 gene. Even if you breed the stallion to a mare who is homozygous recessive for W20, meaning she has no dominant alleles to give, their foal will still have one dominant W20 allele, which produces white in their coats. This leads us to the debate in the paint horse industry. Despite modern knowledge of genetics in homozygous horses, many are excited that solids can now be included into regular registry. Some even want to expand it to horses who do not have genetics to pass on the white genes, as long as they are out of at least one paint parent. While there are some perks to including solids in regular registry, such as widening the gene pool and increasing the value of solid horses already in the industry, I believe that if we continue to loosen requirements, we will ultimately lose the breed that has been a part of American history for so long. So research the rich history of the breed for yourself, and have their beautiful coat patterns shape the development of the breed in APHA. If you have a good grasp of the implications of rule changes, you can develop your position on the matter and advocate to others. Thanks for listening to today's episode.
