Tuesdays with Tony – 5 Panel Testing

Ah, your mare! You look wistfully back on your history with her. You and your mare have accomplished a lot. She’s made your dreams come true; she’s been there as your partner, and companion through thick and thin.  You’re ready for her to carry on her legacy with a foal.  You’ve poured through the magazines, you’ve researched performance records, and you’re a pedigree expert. Your perfect stallion has been found and is even 5 panel testing negative! Oh goody!

What the heck is  5 panel testing? Is it a good thing when a stallion is negative? What’s a positive mean? Never fear, your intrepid feline source of information is here.

Why do I care about 5 panel testing?

Long ago, in a land far, far away horses were bred for speed, muscle, good looks, color.  You name it, humans have bred for it.  Along the way some other stuff was selected for too, on accident.  Beginning about 30 years ago, scientists found a way to test genes to see if some of the not so desirable stuff was present in the DNA of a horse.  

In 2015, the American Quarter Horse Association (AQHA) took the important step of saying “Hey, we can test for a bunch of bad stuff.  Let’s make sure we breed responsibly.”  This means that ALL stallions that file a stallion report now have these results available to you the mare owner.  Many other breeds have their own genetic diseases that are routinely tested for.  Not sure about your breed of choice? Ask the registration association for that breed or check with my minions.  My minions work hard to stay up-to-date on this ever changing world.

What does 5 panel testing test for?

The 5 Panel Test covers, shockingly, 5 major genetic disorders common in Quarter Horses, Appaloosas, and Paints: Hyperkalemic Periodic Paralysis (HYPP), Polysaccharide Storage Myopathy type 1 (PSSM 1), Malignant Hyperthermia (MH), Hereditary Epidermal Regional Dermal Asthenia (HERDA), and Glycogen Branching Enzyme Deficiency (GBED).

These diseases are all caused by one teeny, tiny mutation which makes them easy to test for, and they all cause really bad diseases. I put a short description about all of them at the bottom of this blog in case you want to read more about them.

Should I test my mare?

You really should.  That’s the short answer.  Here’s the long one.  You can never have too much information when it comes to breeding.  Additionally, HYPP, PSSM, and MH could cause health problems for your mare during pregnancy so knowing if she’s got them can be very helpful to your wonderful veterinarians.  

You really, really should do the 5 panel testing if your stallion choice is positive for any of them.  If you have found that perfect hunk of a guy for your mare, but he’s positive for one of these diseases, you really need to know if your mare is positive too.  If she is, you are definitely going to have to go back to the pretty pictures and find her a different guy.

I’m pretty sure I can now pass a test on this 5 panel testing! Want more information? Call, text, or e-mail my humans.  They love talking about mares, and babies, and stallions, okay, pretty much anything horse.  Until next week, may your litter box be clean and your food bowl full.

HYPP
HYPP stands for Hyperkalemic Periodic Paralysis. This disease affects the electrical impulses within the body that control muscle contraction. The defective gene results in clinical signs of muscle tremors and fasciculations. In some severe cases, horses may be unable to stand, or even unable to breathe. Horses can show symptoms with only one copy of the defective gene, but symptoms are often more severe if they have two copies of the mutation. This disease affects mostly halter horses, and can be traced back to the prolific stallion ‘Impressive’. Since Impressive lines were also used in Paint and Appaloosa halter breeding programs, HYPP is found in those breeds as well. AQHA does not allow registration of foals that test positive for two copies of the defective gene (H/H), but will allow registration of foals that are H/N: one defective and one normal gene.

PSSM 1
PSSM stands for Polysaccharide Storage Myopathy. This disease causes changes in the way sugars are stored and used by the muscles. It causes frequent episodes of ‘tying up’ if not properly controlled by a special diet and regular low intensity exercise. There are two types of PSSM. Type 1 is caused by a genetically identified mutation, which is testable. Type 2 is suspected to be genetic, but that mutation has not yet been identified by researchers. Most Quarter Horses with PSSM have type 1. Horses will show symptoms of PSSM type 1 with one or two copies of the mutation.  Like HYPP, PSSM type 1 is more common in halter QHs than in other lines. Some QHs have been shown to have mutations for both HYPP and PSSM.

HERDA
HERDA stands for Hereditary Epidermal Regional Dermal Asthenia. Horses with HERDA have defective collagen, an important protein that is part of skin, cartilage, muscles, and tendons. The major clinical sign is skin that is easily injured, torn, or even sloughed off. The skin is also very slow to heal. There is no treatment for the condition, and horses that have it are often euthanized. Horses will only show symptoms if they have two copies of the mutation for HERDA. Horses with only one copy of the mutation are clinically normal. These animals are called ‘carriers’. They can pass copies of the mutation to their foals, and if one carrier is bred to another carrier, the foal might inherit the mutation from both parents and be symptomatic. HERDA is limited mostly to horses with reining and cutting horse bloodlines.

GBED
GBED stands for Glycogen Branching Enzyme Deficiency. Like PSSM, this disease also affects how sugars are stored, but in a different and more severe way. It results in abortions, stillborn foals, and foals that are alive but weak at birth and die or are euthanized soon after. Like with HERDA, horses may be carriers for GBED – if a horse has only one copy of the mutation it will be clinically normal. Paints and Appaloosas can also carry the GBED mutation.

MH
MH stands for Malignant Hyperthermia. This disease changes the way muscle cells handle calcium, and thus the metabolism of the cell. Horses with MH will appear normal most of the time, but have specific occasions when they show symptoms. During an attack, horses will have a very high fever, profuse sweating, high and irregular heart rate, high blood pressure, and rigid muscles. Attacks are triggered by certain anesthetic agents or stress, and are sometimes fatal. MH is believed to be less common than either HYPP or PSSM, but the percentage of affected horses is not yet known. Several breeds including Quarter Horses and Paints can be affected. Horses may be positive for both PSSM and MH together, and these animals appear to suffer from more severe episodes of tying up than horses that have PSSM alone.