30/04/2024
We've shared this before, but PSSM continues to be talked about with our circles so we are sharing this once more...
The EBRA encourages PSSM1 testing and requires the test for all breeding stallions (though a positive test result does not disqualify them from breeding). Here's why. It is worth noting that a negative PSSM1 DNA test does NOT mean the horse is PSSM negative. A horse can receive a false positive. Also, most draft horses with the genetic mutation for PSSM1 are asymptomatic.
PSSM in draft horses is estimated to have emerged as far back as 1,600 years ago, says Stephanie Valberg, D.V.M., Ph.D.
If the data regarding the incidence of PSSM in Draft-related breeds are even close to accurate, which is up to 86%, it would appear that trying to breed away from this trait in these breeds would be extremely difficult. In fact, there is some suggestion that horses with PSSM, when they can deal with the condition, are superior in temperament, conformation, and even more importantly, performance. (citation: Susan A. Mende, DVM, Dipl ACVP)
"This trait is what allowed the draft horse to survive long hours of fieldwork on poor feed," says Hernando Plata-Madrid, DVM.
Since all draft horses are insulin-sensitive, draft horse owners have already adapted their feed and exercise regimes. So in many ways, they are ahead of the game when it comes to caring for horses who are diagnosed or undiagnosed for PSSM. (citation: Dr Eleanor Kellon, DVM Ph.D)
Most draft horses with the genetic mutation for PSSM1 are asymptomatic. The majority of draft horse owners, including Brabant owners, don't feed their horses starchy foods. Instead, they seek feeds that provide extra calories in the form of fat. Again, for hundreds of years, draft owners have developed food and exercise regimes to best suit the draft horse's slow metabolism functions, says Michael R. Stone, DVM. It just so happens that this regime is the remedy for managing horses with PSSM.
It should be noted that an important part of the management of PSSM horses is daily exercise. This enhances glucose utilization and improves energy metabolism in skeletal muscle. For symptomatic horses: If ONLY the diet changes, approximately 50% of those horses improve. If BOTH diet and exercise are altered, 90% of horses have fewer to no episodes of tying-up.
Tying up is a symptom rather than a specific disorder. There are two categories with tying up, horses that have sporadic/isolated episodes and those that have repeated episodes. Isolated episodes are more likely to be due to management/dietary factors. Common causes include electrolyte imbalances to plain overworking of a horse to heat stroke. (citation: Dr Beth Valentine DVM Ph.D).
So the ultimate question is to breed, or not to breed. Dr. Susan Menda says, "Given the high incidence of PSSM within certain breeds and the apparent performance capabilities of PSSM horses, it may not be feasible or even appropriate to try to breed away from this condition."
Dr. Beth Valentine shares the same view and does not advise trying to breed away from this trait. She believes that working horses may actually benefit from it and that may be why it is so common in so many breeds. The key to managing these horses is to feed the right diet and provide enough exercise.
As stated above, a negative PSSM test does NOT necessarily mean the horse is negative and MOST carriers are asymptomatic.
In the end, the EBRA considers the decision on whether to breed or not to breed a very personal decision with no one-size-fits-all answer. Therefore, we leave those decisions up to the mare and stallion owners.
We welcome any questions you may have. Please email [email protected] or feel free to ask in the comments. We'll do our best to provide a response. If we do not have the answer, we will surely seek it out from our resident expert, Dr. Beth Valentine.
Members, you can also watch Dr. Beth Valentine's clinic on PSSM here: https://www.europeanbrabant.com/forum/health-wellness/pssm-epsm-clinic
