5 Panel Testing
As a responsible Breed Association, ApHANZ Council feels it would be appropriate to introduce 5 Panel Testing. After considerable discussion with our Members, Council put forward the following Remit at the 2016 AGM.
From the commencement of the 2016 breeding season, all classified stallions must be
5 panel tested and certification to be held in the Aphanz office.
This Remit was PASSED.
What is 5 Panel Testing?
5 Panel Testing is a set of DNA tests specifically for the 5 genetic diseases; PSSM1, HERDA, GBED, HYPP and MH. These particular conditions have been identified as commonly being associated with stock horse type breeds which the Appaloosa falls under.
Some quick info to help the following information make sense…
A gene is made up of 2 alleles; one from each parent. Where there are 2 different alleles present (Heterozygous) one allele will be Dominant and one will be Recessive. This means that a Dominant allele only requires 1 allele to “switch on” that trait while the Recessive allele’s effect is masked, where as a Recessive allele will require 2 alleles the same (Homozygous) “switch on” its trait. Positive and Negative test results; this can seem a bit back to front, remember the result is always in reference to the thing that is being tested for; Positive means Yes they have it, Negative means No they don’t have it.
PSSM – Polysaccharide Storage Myopathy – (PSSM1) an inherited muscle disease. The characteristics vary from muscle pain, cramping and cell damage with exercise, to progressive muscle atrophy. PSSM is a dominant disorder, which means a horse only has to carry one copy of the disease to be affected. If the horse tests PSSM positive, he has the disease.
HERDA – Hereditary Equine Regional Dermal Asthenia. The symptom of this disorder is a lack of adhesion within the layers of skin due to a genetic defect in the collagen that holds the skin in place. This defect causes the outer layer of skin to split or separate from the deeper layers, sometimes tearing off completely. Areas under the saddle seem to be most prone to these lesions, often leaving permanent scars and preventing the horse from being ridden.
The disorder is recessive, which means both the sire and the dam must possess at least one copy of the mutated gene in order for the offspring to be afflicted. Offspring born with one copy of the defective gene and one non-defective copy are considered a carrier and have a 50% chance of passing the defective gene on, but are in no way affected by carrying the gene. HERDA only comes into play when you go to breed your horse. If the horse is a carrier, it would be better to only bred it to tested N/N stallions/mares.
GBED – Glycogen Branching Enzyme Deficiency (GBED) is a fatal condition caused by the bodies’ inability to properly store sugar. This means that the horse will not be able to store enough energy to fuel important organs, such as the muscles and brain. Foals born with GBED suffer from a range of symptoms, such as low energy, weakness and difficulty rising. Other symptoms include low body temperature, contracted muscles, seizures, and sudden death. Unfortunately, GBED is always fatal; most affected foals will die before the age of 8 weeks. GBED often causes the foetus to be aborted in utero.
GBED is a recessive trait, a foal can only be affected if the foal inherits the disease from both parents. Horses that are carriers of GBED do not have any symptoms associated with the disorder. This makes DNA testing important to screen for carriers and prevent this fatal condition. GBED only comes into play when you go to breed your horse. If the horse is a carrier, it should only be bred to tested N/N stallions/mares.
HYPP – Equine Hyperkalemic Periodic Paralysis Disease (HYPP) is a muscular disease. Symptoms of HYPP may include muscle twitching, respiratory noises and unpredictable paralysis attacks which can vary in severity from unnoticeable to collapse or sudden death. HYPP is a dominant disorder meaning if a horse tests HYPP positive, he has the disease.
MH – Malignant Hyperthermia is a genetic muscle disorder. Horses with the MH mutation may not show any physical signs of the disorder until triggered by exposure to anesthesia or extreme exercise or stress. Symptoms can include high temperature, increased heart rate, high blood pressure, sweating, acidosis, and muscle rigidity. Symptoms develop rapidly, and if not treated quickly, this condition can be fatal.
MH is a dominant trait, so the disorder can be passed on even if only one parent has the defective gene. The mutation can be present along with PSSM and if a horse also has PSSM, the symptoms associated with MH can be more severe. Therefore, testing for both PSSM and MH is recommended. Although this condition is rare, testing for MH is recommended in case a horse must undergo anesthesia. Horses that are known to have the MH mutation can be given medication prior to administering anesthesia to help reduce the severity of the symptoms.
How to test?
Collecting a sample for testing is simply a case of pulling about 30-40 hairs from the mane or tail ensuring the root of the hairs are present on the sample.
These Tests are now available at Massey University in New Zealand. For full instructions and downloadable forms please go to Equine Parentage and Animal Genetic Services Centre .
These Tests are still available from Animal Genetics in Florida, USA. Complete the Equine Test Submission form (select Quarter Horse Panel) and send off with payment. Cost is $95 US. For full instructions and downloadable forms please go to Animal Genetics.
Where to from here?
At this stage ApHANZ recommends breeders test their horses. Obviously there is a cost associated with this, some people will argue this is an investment.
Going forward, in response to feedback already received, we have passed a remit that Stallions be tested as part of their classification requirement, and to recommend that mare owners get their mares tested prior to breeding, especially in the case where your desired stallion may be a carrier.
If by chance your horse has a positive result on any of the tests this does NOT mean that they will lose their registration status, or that they will be barred from having their progeny registered, or worse.
As always information is the key to making informed decisions about your horses and their potential breedings.