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Equine Genotyping or horse DNA testing, as it is more commonly known, is a unique science that enables horse owners, breeders, and trainers to learn about their animals' genetic traits. It has revolutionized the horse industry, and in this article, we examine its benefits and answer common questions regarding this service.
Why test horses?
Racehorse training is a complex task. It requires handlers to match horses to the races they are most capable of winning, and at the same time, maximize the amount of prize money won.
Trainers usually base their decisions on various factors such as
- their knowledge of individual horse pedigree
- performance in previous races
- progress assessments during training
- daily feedback from the jockeys riding each horse.
Trainers are also increasingly relying on DNA information to facilitate their choices. The reasons for this are simple; a horse's performance is the product of its genetics and environment. While a trainer may have substantial control over the environment, including how the horse is trained, its DNA cannot be changed. Also, studies have revealed that equine DNA has a significant impact on performance. These factors are compelling reasons to gather as much information as possible on horses' genetic makeup.
Identifying hereditary diseases
Most inherited diseases are caused by mutations within a single gene that changes how the body works. They are either dominant or recessive. Inheriting only one copy of a defective dominant gene will affect the foal. If the mutation is recessive, on the other hand, the foal needs to inherit two copies of the defective gene (one from each parent) to be affected.
A horse with only one copy of the recessive gene is known as a carrier. He or she may be completely healthy but is capable of producing offspring with the disease when mated to another carrier.
DNA testing can help owners identify the following conditions
- Glycogen branching enzyme deficiency (GBED), a fatal condition in which the body fails to store glycogen. It results in progressive weakness and organic failure.
- (HERDA) hereditary equine regional dermal asthenia - a connective-tissue disorder that causes fragile skin. The skin tears easily and is slow to heal, and prone to infections. Horses with this condition are often euthanized as it is the most humane thing to do.
- Malignant hyperthermia: an illness in which significant exercise, stress, or anesthesia triggers fever, muscle rigidity, excessive sweating, shallow breathing, and an irregular heart rate.
- HYPP (hyperkalemic periodic paralysis): a condition where the horse experiences episodes of tremors and muscle weakness. In serious cases, he or she may collapse and suffer cardiac or respiratory failure.
- Polysaccharide storage myopathy: this causes an irregular accumulation of sugars in the muscles, leading to tremors, cramping, and unusually dark urine as the kidneys filter muscle-damage byproducts from the blood.
- Functional epidermolysis bullosa (JEB). This condition is a hereditary autosomal recessive trait that is observed in Belgian Drafts and American Saddlebred horses. Foals with JEB are born with moderate to suffer skin deformations like erosions or ulcera, blisters, and mucocutaneous epithelia. The condition often worsens as the foals grow, so they must be euthanized early. Since it is a recessive trait, JEB foals often arise from mating two JEB-Carriers, which do not show any noticeable signs of the condition.
Besides enabling breeders to sort between healthy and affected animals, it allows them to find carriers. Consequently, it is a vital tool for avoiding the production of unviable or affected foals.
Note: PSSM1 testing is mandatory for all quarter horse breeding stallions. However, the disease has also been discovered in more than 20 breeds, including warmbloods with European ancestry and American stock hoses.
DIY equine DNA testing kit instructions
- You'll be asked to download and answer a sample submission and DNA submission form for each horse
- Gather scotch tape (cellophane), plain paper envelopes for each DNA sample, along with a paper mailing envelope that you will use to send all the DNA samples to the testing company.
- You will need to follow the specific instructions provided with your kit, you will generally be asked to pull (not cut) hair samples from the horse's mane above the withers. You should pull 12-25 hairs by coiling a strand around your finger close to the skin and pulling quickly and evenly. The DNA is contained in the follicle, so this section of the hair must remain undamaged. Study your hair samples to ensure they have not been broken off before the root. For young foals, the hair from the mane is usually finer with a small follicle, so you should pull hair from the foal's tail instead.
- Put the hairs in a straight line across the middle of the form provided with the testing kit. It will usually have an area reserved for samples.
- Use the scotch tape you procured earlier to secure the hair shafts, so the sample stays in place. Do not put the tape on the root bulbs. Fold the sample as you would a business letter.
Note: to prevent sample contamination, you should not brush your horse's mane with a brush that may have another horse's hair in it. You could unintentionally add the other horse's hair to the sample.
Do all horses have unique DNA?
Yes, but there are exceptions. All individuals have unique DNA except for identical twins (also known as monozygotic twin horses). Identical twins are very rare in horses and are the result of a fertilized egg splitting. Dizygotic or fraternal twins are more common, and they occur when two follicles ripen each ova they produce is independent fertilized.
Can I get proof of parentage for a foal?
Using DNA tests to verify a foal's parentage requires samples from three parties: the dam, sire, and foal. DNA analysis can verify whether the sire and damsel created the foal by comparing the genotypes from all three horses.
Equine DNA testing is a beneficial tool for horse breeders, owners, and trainers, and it's only going to get better. As the science continues to evolve, researchers will continue refining the process and identifying new genetic trait markers, making it an indispensable industry tool.