06/11/2025
My metabolic horses
I wanted to share my experience with metabolic genetic disorders.
I have 4 horses with PSSM type 1 in my care.
What is PSSM?
PolySacharide Storage Myopathy is a genetic disorder which affects how horses store glycogen. There are a number of variants that affect horses differently.
Symptoms of a PSSM type 1 ' attack' include:
Muscle stiffness
Tying up
Excessive sweating
Reluctance to move
Shifting lameness
Tremors along the flanks
One of my PSSM positive horses has been with me for 12 years, and turns 20 this year. He has won multiple National championships in ridden classes, and has yet to present an obvious symptom/attack. We know about his status through genetic testing required by breed societies.
His son is also PSSM positive and has also had no symptoms/attacks.
One mare is only 5 and is just starting her riding career, she has also never had an episode.
The other gelding was stabled for 12 hours. day before coming to me, and developed ulcers. Since being with me he has shown no symptoms of PSSM and his riding is coming along nicely.
Does that mean that the PSSM type 1 is a non-issue? I feel PSSM type 1, which is the only variant I have direct experience of, is like a massive highlighter to issues with how we, as an industry manage horses.
The reason I don't have symptoms show up in my herd is not because I manage them differently to the other horses in my care, but because of how I manage all horses.
All my horses live out 24)7, year round, in a herd setting with large spacious paddocks. There are some grasses in their paddocks that aren't ideal, but they are mixed with natural uncultivated wild grasses. Most importantly, the horses move. They move often and cover ground.
We don't have a track system, because with the low-nutrition wild grasses they would lose too much weight having grass restricted in any way. They do have to walk from water source to the various different grass areas. Nature does a good job of making them move. As the horses graze and area the grass gets stressed and releases pheromones which make it less palatable. The horses move to a different grazing spot until that grass ' sours'.
I feed concentrated ' hard feed' to supplement protein, vitamins and minerals, but I avoid feed with high sugars. Too often people hear sugar and think molasses, but with horse nutrition we are actually talking about Non- Structural Carbohydrates ( NSC's). Molasses IS a NSC, but so is corn/maize and oats i(ncluding oat hay).
The feed I choose for my herd has. low molasses content and is grain free.
When it comea to riding and 'training' my approach to all horses is helpful for PSSM positive horses.
Physical fitness is developed slowly, while emotional fitness is prioritized. The herd have a baseline fitness from living out with other horses, but carrying a rider requires a different kind of fitness. One of the symptoms of PSSM is ' exercise resistance', where horses have tying up episodes after being exposed to physical exertion. This is where, I believe, conventional training programs do damage to any horse, but PSSM horses show clear veterinary issues.
Taking a horse from doing nothing and making it run for 20 minutes without preparing it causes fatigue. Adding a rider to that horses and having them run, jump, spin and contort into fancy " shapes' is an unfair expectation on any horse if we don't gradually increase their workload, allowing them to build strength and fitness.
I see PSSM type 1 as the ' canary in the mind shaft" pointing out whats wrong in the way we keep and train horses.
PSSM is genetic and has a 50% chance of passing down to offspring. My old man produced and incredible PSSM negative son, who did very well in the showring, and the PSSM positive son, among his progeny. I would, personally, be happy to breed a PSSM horse to clear horse amd risk the 50% chance of PSSM in progeny, BUT if I the resulting foal was positive, they would never leave my care. I don't want any of the horses in my care moving to the possibility of conventional set ups, but a PSSM horse in a conventional set up, with conventional methods, will live a tortured life. I would make the hard decision to PTS before they ever left my care.
I realize that some people will be reading this for ideas on how to manage their metabolic horses, and don't have the option of hectares of mountain range to graze their horses on. I do recommend finding a well managed track livery. I would never stable a PSSM type 1 horse. Even for stall rest from an injury.
When I take horses to shows, I try have outside pens rather than stables. Butbif I need to stable I make sure they gonfor walks out every few hours.. I feel that applies to most metabolic horses. Movement is critical. On the flipside, turn-out in smaller, pasture grass paddocks, where the horses moves a few steps at a time to get to water etc. Can also be problematic. This isn't something unique to horses with genetic ' disorders', many horses develop health issues in those settings. As a standard, the way we keep horses is in need of an urgent overhaul.