The right feed for horses with PSSM 2


Small intestine digestible protein is the keyword when it comes to feeding horses with PSSM 2. But you can do even more good for the horses.

  • What is PSSM 2?
  • How does PSSM 2 manifest itself?
  • Which horses are affected?
  • Which feed is good?
  • How should the training be designed?

What is PSSM 2?

With increasing research in the field of muscle diseases, more and more horses with the typical muscular symptoms of PSSM 1 have been found in recent years, but they did not have the GYS1 mutation typical of PSSM 1. Rather, mutations of other gene loci were found. Therefore, the collective term "PSSM 2" was initially created for all stress myopathies or neuromuscular diseases that do not have the GYS1 mutation (PSSM 1).

PSSM 2 currently includes gene mutations in 6 risk alleles: P2, P3, P4, Px, P8 and K1. Researchers suspect further risk alleles. The severity of the symptoms depends on which mutation occurs, whether several genes are affected and whether the mutation is homozygous or heterozygous.

In PSSM 2, the mutation-related changes do not affect the sugar metabolism of the cell, but rather the structural composition of the muscle fibres. This means that the muscle becomes "fragile". With the mutation of the P8 allele, the antioxidant system of the muscle is also affected.

Horses with PSSM 1 have a GYS1 gene defect in contrast to those with PSSM 2. What consequences this has and what is important for feeding with PSSM 1, you can read in this article:

How does PSSM 2 manifest itself?

Overall, the mutations in PSSM 2 often manifest themselves in the form of tension, gait irregularities, reluctance to move, changing, recurring lameness, behavioural changes and even painful muscle breakdown (e.g. visible as grooves or muscle dents). The course is relapsing and progressive. Relapses can be triggered, for example, by operations, injury breaks, vaccinations or other energy-sapping phases, especially in connection with low-protein feeding.

Which horses are affected?

All breeds are affected, especially higher blooded, lightly muscled breeds. The first symptoms usually appear at about 8 years of age.


Which feed is good?

Due to the genetic defect, the body consumes more protein to "improvise" the building of the muscle. Affected horses therefore benefit from a ration with a higher content of protein that can be digested in the small intestine. In addition, the quality of the amino acids of the protein should be as high as possible. This means that the protein should have a high content of essential amino acids (such as lysine, methionine, threonine, etc.). Special high-protein feeds, such as marstall MyoCare Muesli or the targeted administration of amino acid supplements, such as marstall Amino-Muscle Plus, are very important for maintaining or rebuilding the muscles.

Cereal free and low-sugar feeding has become established in PSSM 2, but is probably not absolutely necessary. However, supplements of omega-3 rich linseed oil are advisable. In addition, the horses need a slightly increased supply of magnesium, sodium chloride (salt), as well as plenty of vitamin E (> 2,000 mg vitamin E per day). Antioxidants such as vitamin E and C are especially important for horses with P8, but also support horses with the other genetic defects. Trace elements such as zinc, manganese, copper and especially selenium (1.8 mg per day) should not be fed excessively, but to cover requirements. As a rule, grazing does not have to be restricted in PSSM 2 horses.

Product recommendation

How should the training be designed?

Training horses with PSSM 2 should include longer warm-up and warm-down periods as well as breaks for muscle relaxation. The horses also need a lot of patience and understanding from their riders and handlers. If a PSSM 2 horse is exposed to little stress or if it is fed and kept ideally, it can even remain symptom-free or show only minor symptoms. Therefore, care should be taken to minimise stressful conditions and events.

Definition of terms:

PSSM is the abbreviation for Polysaccharide Storage Myopathy or PolySaccharide Storage Myopathy and refers to a glycogen storage disorder. It is divided into PSSM 1 and PSSM 2, although the term only really applies to PSSM 1.

PSSM 1has been scientifically researched for about 15 years and is a hereditary poly-saccharide storage myopathy caused by a mutation of the GYS1 gene. Affected horses require grain-free and low-sugar rations in order to remain efficient.

PSSM 2 is a collective term for various neuromuscular diseases that have similar symptoms but do not have the typical GYS1 gene defect of PSSM 1. The horses benefit from supplements of small intestine digestible protein with many essential amino acids.

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