AQHA Magazine July August 2019 AQHA July-Aug 2019 Final | Page 24

PG.22
HORSE HEALTH
IS MY HORSE
TYING-UP?
TYING-UP AND EQUINE POLYSACCHARIDE STORAGE MYOPATHY
(EPSSM OR PSSM) IN QUARTER HORSES
P
SSM is an inherited form of exercise
rhabdomyolysis or muscle breakdown found in
over 20 breeds of horses. That it could occur in
so many different breeds may seem amazing,
but given the common origins of most breeds, it’s
not so surprising. Add to this the finding that horses
with PSSM are often outstanding in conformation,
performance and temperament, and it’s easy to
understand the high prevalence!
Healthy muscles are essential for optimum
performance and even minor problems will reduce
power output, coordination, stamina and willingness
to exercise. Because muscles are complex things that
require a multitude of different electrolytes, enzymes,
proteins, sugars and training to function there are
many conditions that affect their performance.
Unfortunately, muscular disorders are not uncommon
in horses and the most frequent clinical problem
is ‘tying-up’ (exercise-induced rhabdomyolysis or
ER) which damages muscles and causes painful,
uncontrollable and continuous contractions. Horses
can show a range of symptoms - some are obvious
(refusal to move, hard muscles, colic), while in others
signs may be so mild they require careful examination
and veterinary diagnostic tests.
The most common form of tying-up is ER. ER is caused
by external factors such as: strenuous exercise in an
unfit horse, stress, dietary imbalances, high grain
intake and lack of exercise after a period of over-
feeding and under-exercising; electrolyte imbalances;
infection; a low fibre/high carb diet, or amino acid,
selenium, magnesium, vitamin B1 and E deficiencies.
It has been recognised in working horses for over
100 years. Also known as Monday morning disease,
azoturia or exertional rhabdomyolysis (ER), any horse
can experience an episode at some point in their life.
But… there is also a recurring, chronic form of tying-
up, and in the last 20 years we have learned that in
AUSTRALIAN QUARTER HORSE ASSOCIATION