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POOR PERFORMANCE
Musculo-skeletal disease
Low-grade lameness, especially of the hind
limbs can be slow in onset and surprisingly
difficult for the owner/rider to detect.
Similarly, fore-limb lameness affecting both
limbs (bi-lateral) may not be as obvious as
one may suspect, though both are a very
common cause of poor performance.
Further investigation is warranted in a high
proportion of cases and so nerve blocks/
joint anaesthesia, x-rays, ultrasound scans,
scintigraphy and MRI scans may be
necessary to localise and image the area
causing the problem.
Back and pelvic problems can present to us
as a reduction in performance, for example,
sacro-iliac strains are common in horses
which perform jumping disciplines, or have to
move at speed. Back pain is often secondary
to low grade lameness and so one must be
aware that by treating the back pain we may
not, in fact, be treating the cause.
Another musculo-skeletal reason for poor
performance is recurrent exertional
rhabdomyolysis (RER), also known as tying-up
or azoturia. This is a milder form of the
condition which many owners may have seen
when a horse either at, or immediately after,
exercise appears to be suddenly very stiff
and in great pain. Diagnosis may be assisted
by an exercise tolerance test - a blood
sample is taken pre-exercise and again
several hours after exercise. The muscle
enzymes are measured in each sample and
a comparison of the two may suggest RER.
Respiratory disease
This can be divided into upper and lower
respiratory disease.
●
Problems of the larynx and throat
which cause restriction of the air flow
into the lungs are examples of upper
respiratory disease.
●
Respiratory infections/inflammatory airway
disease/recurrent airway obstruction
(formerly known as COPD) are lung
problems which are examples of lower
respiratory disease.
Diseases of the upper and lower respiratory
tract will require an examination with an
endoscope to facilitate diagnosis. This may
be done with or without sedation, or on a
treadmill to simulate exercise. In the last few
years, an endoscope has been developed
which can be placed in the horse's nose and
secured onto the tack allowing the horse to
be exercised on a gallop at the same time as
the images are viewed remotely.
Gastro-intestinal disease
Dental disease may lead to oral pain and
poor performance. This would be most
common in dressage horses. A thorough
dental examination using a torch, mirror and
sedation would identify most problems likely
to cause pain. Further investigations may be
necessary and can include x-rays of the head
to image the teeth and identify fractures
or infections.
Gastric ulceration is a common cause of
poor performance. Signs may also include:
irritable behaviour, variable appetite, poor
condition, poor quality hair coat and mild
recurrent colic.
Ulcers of the stomach can be viewed
directly through a gastroscope - a relatively
straightforward procedure carried out under
mild sedation.
Cardio-vascular disease
Problems of the heart and circulation which
cause poor performance are uncommon.
If there is an abnormal heart rhythm, or
a leaking heart valve, there may be
insufficient blood flow at maximal exercise
to maintain performance.
Heart murmurs are very common in horses,
but heart disease causing poor performance
is uncommon. This means that very few
murmurs are clinically significant.
Many abnormalities of the heart can be
identified during a clinical examination.
Further investigation may involve blood
tests, an ECG (at rest and/or at exercise)
or an ultrasound scan of the heart.
Systemic illness
Viral infections, such as equine herpes virus
(EHV) or bacterial infections such as
Streptococcus equi 'strangles' may lead
to systemic illness and poor performance.
In the early stages of these infections, there
may be other signs of the disease visible
to the owner.
Conclusion
If your horse is performing poorly, contact
your XLVets Equine practice to discuss
the problem and begin an investigation.
Only in a very small number of cases
can a diagnosis be made at the first
examination - usually a detailed and
logical investigation must be carried out
in an appropriate methodical manner so
that common conditions are not missed.
Once a diagnosis is made, a treatment
plan can be formulated and a prognosis
for likely return to work can be given.
The causes of poor performance
can be categorised according to
the body systems:
●
musculo-skeletal - this is probably
the most common reason for
poor performance
●
respiratory system - also a very
common cause
●
gastro-intestinal
●
cardio-vascular
●
systemic illness
SPRING 2013 ISSUE
EQUINE MATTERS
4
Dental examination of a pony to look for any
abnormalities that may affect performance