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Hyperlipaemia is an important condition in ponies and
donkeys, not just because of the
seriousness of the clinical signs and biochemical
changes involved, but because of the distress it
causes owners and breeders that have had animals
suffer from it.
Hyperlipaemia occurs most commonly in fat animals in late
pregnancy and is rarely seen in larger horses. The syndrome
has similarities with conditions in other species but the
definitive aetiologies are not yet known. The condition in
ponies is undoubtedly related to stress. The biochemical
mechanisms involved in equine hyperlipaemia are considered
and an hypothesis of possible pathogenesis is put forward.
This hypothesis is tested by presenting the results of a
preliminary study to evaluate glucose and lipid metabolism
in horses and ponies. It appears that the pony is markedly
insensitive to insulin compared to larger horses which
means that triglycerides are more readily mobilised and the
animal is therefore susceptible to hyperlipaemia in a
situation of negative energy balance. The effect of stress
is to increase cortisol levels which only exacerbates the
insulin insensitivity and so creates a vicious circle. The
importance of an innate insulin insensitivity may also be
important in the pathogenesis of such conditions as
(photo: the donkey
When the donkey stops eating enough, the essential organs
still require a food supply, so the body tries to use the
energy that is stored as fat deposits. The result is that
free fatty acids are circulated to the liver to be
converted to glucose for use by the body. This system is
controlled by complex hormonal events, which should shut
down the amount of fat released from fat stores as the
liver produces the glucose for the body.
Sadly donkeys and small ponies are not able to efficiently
turn off the fat release and the blood soon fills up with
excess fat in circulation. This circulating fat can be
measured in the blood as triglycerides by your veterinary
Large amounts of fat cause the liver and kidneys to
degenerate and fail, and eventually all the organs in the
body fail, this results in irreversible damage and death
follows soon after.
• Small pony breeds eg Shetlands, Welsh Mountain,
Miniatures. Uncommon in horse breeds, but has been
• Females more than stallions/geldings (only partly due to
pregnancy and lactation).
• Stress (transport, weather, disease).
• Age: increased risk with age. Age related decline in
insulin sensitivity. Unusual < 18 months.
• Underlying primary disease (parasites, enteritis,
colitis, impaction, dysphagia, choke, dental problems,
• Hyperadrenocorticism (Cushing’s disease).
• Metritis, Hepatopathy, Peritonitis.
Dull, depressed, anorexic, pyrexic,
tachycardia, tachypnoea, gut stasis (dry mucous covered
faeces), ataxia, oedema, congested mucous membranes,
halitosis, hepatic encephalopathy, ‘sham’ eating and
drinking. Later there may be ventral oedema, and signs of
liver and kidney failure such as head pressing, circling
Your vet should take blood samples early in clinical
examination. A diagnosis of hyperlipaemia is confirmed by a
plasma triglyceride concentration and the hepatic and renal
1. Prompt treatment is essential where diagnosis possible.
Consider parasites in all cases. Wean foals early.
2. Fluid therapy.
3. Symptomatic therapy: anti-inflammatories, anti-gastric
ulcer therapy, multivitamins, anabolics, plasma
4. Nutritional support: maintain a positive energy balance.
If the animal is very sick your vet may need to provide
energy to the donkey via a stomach tube or intravenous
5. Normalis lipid metabolism with insulin, glucose and/or
• It is always contra-indicated to use glucocorticoids.
• Keep companions together.
• Assess likely ‘stress’ of hospitalising patient, may
prefer to treat at home.
• Owner attitude is vital: if they are willing to hand
feed, oral drench and administer oral medicins, the
prognosis will be much better.
• Always encourage and try to maintain voluntary feed
• Discuss finances early in disease.
The condition has a high mortality rate (including
euthanasia) of between 60 and 100 per cent, and a reported
prevalence of between 5 and 11 per cent in ponies and 18
per cent in donkeys in referral hospital populations. In
view of the poor prognosis, it highlights the importance of
client education in disease prevention.
More about donkeys and
hyperlipaemia: The Donkey