Hyperlipaemia is a metabolic disorder which predominately
affects pony breeds, although larger breeds of horses can also
be susceptible. Studies have indicated that up to 5% of ponies on
studs in Victoria develop the condition each year.
Hyperlipaemia is a life threatening metabolic condition with
an inherited risk in certain bloodlines of ponies. However,
the main trigger for onset is rapid reduction of feed intake
in heavily conditioned ponies, with heavily pregnant and
lactating mares requiring a high energy demand being the
most susceptible. It has also been reported in fasting or
Another condition with a similar sounding name is hyperlipidaemia,
which relates to excess blood levels of lipids or fats. It is a
common finding in horses and ponies following exercise or reduced
energy intake due to colic, surgery and short periods without
Hyperlipaempia is caused by the body’s natural reaction to
mobilise fat reserves for energy, thereby increasing circulating
lipids (fats) in the blood. It is not life-threatening and is a transient
normal reaction, except in ponies and donkeys where it can be a
predisposing cause of hyperlipaemia.
Hyperlipaemia in susceptible ponies on the other hand is
a complex metabolic condition which can invariably result
in death within 10 days if the symptoms are not recognized
early and expert veterinary intervention and nutritional
management is not carried out.
In a normal healthy horse, most of the fat or lipids circulating in
the blood to provide energy and omega fatty acids to the cells is in
the form of a very low density lipo-protein (fat-protein complexes),
produced in the liver.
Although some fatty acids can be used to provide energy to
maintain body functions, when higher levels are released and form
longer chain lipo-protein complexes in the liver, they are unable to
be metabolised and begin to accumulate in the liver and blood.
It is most common in overweight middle-aged and aged ponies,
especially those that have developed insulin resistance and a ‘cresty’
neck, which is the underlying trigger for insulin induced laminitis
and metabolical Cushing’s Disease and associated laminitis.
The insulin hormone, which controls blood sugar levels, is
also required for the activation of a lipo-protein enzyme, lipoprotein
lipase, which breaks down these fat reserves as they
pass through the liver. In a pony at risk of mobilising lipoprotein
complexes which are unable to be broken down due
to associated insulin resistance, the complexes accumulate
in the blood and metabolic function is interrupted, with
increased risk of high blood lipo-protein levels, culminating
in liver and kidney failure. Both these organs develop a fatty
infiltration which makes them appear and feel greasy on post
Obese, overweight ponies, especially heavily pregnant
and lactating mares, have the highest risk of developing
hyperlipaemia when there is a sudden shortage of food,
requiring them to revert to use stored fat as an energy source.
As little as 12-24 hours of negative energy balance without hard
feed or ability to graze can trigger the dangerous and potentially
fatal lipo-protein build-up.
Hyperlipaemia is linked to snow falls, heavy, flooding rain
and bushfires where food supply is interrupted or grazing is
severely restricted, rather than a slow onset of food reduction,
such as occurs in a drought or drying off of summer pasture.
The condition is most common in cold, wintery conditions, or
ponies grazing poor quality feed when the demand for energy
is increased and fat reserves are mobilised to fuel metabolism,
superimposed by the higher demands of pregnancy or lactation
in pony mares. Long distance transport and severe sickness, such
as colic, immobility and lameness (laminitis, bone fracture, hoof
infections), tooth problems, heavy worm burdens and viral disease
(such as Equine Herpes and Equine Influenza) can all reduce a
pony’s ability to graze and maintain a regular uptake of sugars and
insulin activity, which also regulates the lipo-protein enzyme.
Early warning signs include a history of severe stress, food
restriction or inability to graze due to weather, lameness or
severe disease which triggers the onset of metabolically induced
Signs include a loss of appetite even when food is offered
after the cascade of liver and blood lipo-protein accumulation
occurs, depression, diarrhoea, drowsiness, weakness and
reduced vitality and well being.
As the condition progresses over 3-5 days, ponies stop drinking,
become inco-ordinated, develop a fever, soft swelling in the lower
limbs (oedema), muscle twitches, colicky signs, with collapse and
death in 8-10 days from onset due to liver and kidney failure.
Elevated blood levels of the stress hormone, cortisol, along with
low insulin secretion, increases the risk of hyperlipaemia.
The overall prognosis is poor in ponies and donkeys 4-5
days after onset, with between 45% and 85% of ponies dying
despite extensive and expensive veterinary support and
A blood sample will reveal a cloudy serum with triglyceride
concentrations above 500mg/dl, or even up to 1500mg/dl in
severe cases. If the serum triglyceride concentration remains below
500mg/dl as occurs with the hyperlipidaemia state, the clinical signs
rarely develop into those typical of hyperlipaemia. Liver enzyme
concentrations are also elevated as liver, kidney and organ failure
develops. A liver biopsy will reveal fatty infiltration, which in severe
cases, may rupture due to excess lipo-protein build-up, which then
results in rapid collapse and death.
Whether hyperlipaemia is primarily due to a sudden food restriction
or a disease process, once the serum triglyceride levels increase
above 500mg/dl, it is difficult to manage and treat successfully in
the short time of 5-7 days before liver and kidney failure develops.
However, if the early warning signs are observed and nutritional
support is provided with a low fat, high energy diet, then recovery
is possible up to 4-5 days after onset of the condition.
Treat any primary disease process, such as investigating reasons for
lameness, relieving colic and managing laminitis.
1.Ensure that the pony is provided with a low-fat, highly digestible
diet, split into a number of feeds per day, to help maintain a
more constant blood sugar level to limit the mobilisation of fat
and build-up of lipo-protein complexes in the liver and blood.
A dampened feed made of 1kg millrun, 2kg crushed oats
or boiled barley to encourage eating, 400g white chaff, 400g
lucerne chaff, 200g Speedi-Beet (soaked in water for 10 minutes)
sweetened to taste with 300g (1 cupful) of molasses and 30g
of salt in 2 cupsful of warm water, provides a high energy,
low fat, palatable feed to
tempt ponies to eat. The
addition of 100g glucose
or dextrose boosts energy
intake to help limit fat
mobilisation and maintain
insulin activity. This mix,
with only half the chaff,
can be mixed into a gruel
in 3 times its volume
of warm water and
administered by stomach
tube into a pony at the
rate of 1 litre/100kg body
weight 4 times per day
until the animal starts to
eat voluntarily once again.
2. Veterinary treatment includes injections of Heparin, an anticlotting
agent which helps to reduce plasma triglyceride levels,
along with glucose drips and insulin injections, have been found
to be helpful in minimising the build-up of harmful long chain
lipo-protein complexes in the liver. Consult your own vet for
The risk of hyperlipaemia can be minimised by ensuring that
susceptible, overweight ponies (and donkeys) are provided
with good quality feeds, preferably fed twice per day, especially
when heavily pregnant or lactating under adverse cold, very wet
conditions, or during long distance transport. One report of
hyperlipaemia in a donkey treated at the Werribee University
Clinic linked relocation of a heavily pregnant jenny with grass
hay she would not eat over a 3 week period in a paddock she
shared with 2 gelding donkeys which ate the hay and did not
develop hyperlipaemia. Maintaining ponies in moderate condition
by carefully limiting feed intake to avoid excess body weight,
particularly as they age and are prone to glucose intolerance and
insulin resistance is also an important preventative means of
management. Consult your vet for advice