FEEDING THE HORSE WITH PSSM TYPE 1

As a dysregulated glycogen storage process  in the muscles is the root of the problem for horses with PSSM type 1, it is essential to limit the horse’s sugar intake. The rule of thumb for feeding a horse with PSSM type 1 is that all feed must be lower than 12% sugar, preferably lower than 10% and preferable even lower than that. This applies to both roughage and “grain” as well as treats that the horse may get. Most commercially available horse treats contain too much sugar for a horse with PSSM1`and the same goes for most fruits. Note: carbohydrates and starch are also (converted to) sugar!

Horses with PSSM type 1 overstore glycogen and free it up too slowly, making it essential to prevent peaks in its sugar intake, since a peak intake will quickly lead to exceeding the maximum sugar storage capacity, which sets the horse up for an episode. This illustrates why feeding even a small amount of fruit or a piece of bread can tip a horse over the edge. Sugar content in grass varies throughout the day and depending on weather, temperature, moisture, type of grass and other factors. This instability makes grass unsuitable for most horses with PSSM type 1. Some horses with PSSM type 1 can tolerate limited grass intake, for example being hand grazed or turned out for a limited time wearing a grazing mask.

Some horse feed is not necessarily high in sugars, but high in carbohydrates. Carbohydrates are converted to sugars once ingested, which makes foods high in carbohydrates unsuitable for horses with PSSM type 1. Grains are high in carbohydrates and therefore not suitable for horses with PSSM type 1. Check the labels on your horse’s feed and add up sugar + carbohydrates (sometimes also listed as starch) to calculate the actual total sugar content.

The point is probably clear by now, but be aware of feeding your PSSM type 1 horse sugar rich foods such as grains, fruit, commercial horse treats, molasses, bread, sugar cubes, corn, etc.

Like for any horse, roughage is the base for a diet for horse with PSSM type 1. Unfortunately, there is no way of telling how rich in sugars hay is by just looking at it or smelling it. Testing is the only way to know. If testing is not an option in your situation, observe your horse carefully to check for any adverse effects.

Hay usually provides sufficient energy to a horse. Only when the energy the horse ingests through hay is not sufficient to provide the fuel for its bodily processes + added exercise do you need to add energy. A good alternative to sugar as a source of energy is fat. Suitable sources of fat for horses are for example: linseed oil or micronized linseed, safflower oil or coconut oil, in quantities of one to two cups a day (100-500 ml), depending on need. It is a good idea to introduce fats slowly and to make sure you are not feeding more fat than the horse actually needs. A horse that ingests more fats than it needs for the exercise it gets runs the risk of becoming insulin resistant.

Other than energy, hay provides a wide array of nutrients that are essential for a horse to thrive. A hay analysis provides the best starting point for a proper calculation as a starting point for your choice of supplementation. Where hay analysis is not an option, a balancer especially created for you geographic location is most likely the best match to compensate for nutrients that are off-ratio. When choosing a balancer, don’t forget to check the sugar content!

Many owners of horses with PSSM type 1 have found that adding extra magnesium (8-15 grams) to the horse’s diet is beneficial for keeping the horse’s muscles soft. A surplus of calcium can hinder the uptake of magnesium, so supplementing calcium is not recommended for a horse with PSSM type 1.

Most horses with PSSM type 1 benefit from additional vitamin E (2000-10000 IU). Vitamin E is  abundant in fresh greens, but since most horses with PSSM type 1 can’t tolerate grass, it is important to supplement. Natural vitamin E has better absorption compared to synthetic vitamin E. An excess of vitamin E can make a horse reactive, so it is important to keep evaluating the amount of vitamin E in the horse’s diet. As selenium promotes the absorption of vitamin E, most vitamin E supplements also contain selenium. Selenium is toxic in high doses, which is why most supplements contain a minimal amount. However, since a selenium deficiency can cause muscle issues, checking your hay or the region it was harvested from for selenium content might be a good exercise. Alternatively, a blood analysis could provide more insight. Discuss this with your veterinarian.

Contrary to people, most horses do not get enough salt in their diet. Salt is important for providing electrolytes to the body. Electrolytes are important for muscle functionality and therefore an important part of the diet for a horse with PSSM type 1. Having a salt lick available at all times is a good idea, but supplementing salt by adding salt (15-40 grams) to the horse’s feed is usually warranted.

Every horse is an individual. Keep observing your horse for changes (better or worse) to see if anything needs tweaking.