Unlike the horse, most donkeys in the UK are kept as pets. The fact that donkeys are now popular pets means veterinary professionals see them more frequently for treatment in equine practice. Donkeys are particularly prone to a life-threatening disorder known as hyperlipaemia.
All registered veterinary nurses (RVNs) working with donkeys should have a good knowledge of the risk factors, clinical signs and treatment options for hyperlipaemia to ensure that effective nursing care is applied. This will give affected patients the best chance of recovery.
Hyperlipaemia occurs when a donkey stops eating and develops a state called “negative energy balance”, in which more energy is used than taken in. The essential organs still require a food supply, so the body tries to use the energy that is stored as fat deposits. As a result of this process, free fatty acids are circulated to the liver to be converted to glucose for use by the body.
Hyperlipaemia occurs when a donkey stops eating and develops a state called ‘negative energy balance’, in which more energy is used than taken in
This system is controlled by complex hormonal events that should shut down the amount of fat released from fat stores as the liver produces the glucose for the body. However, donkeys and small ponies are not able to efficiently turn off this release of fat, and the blood soon carries excess fat in circulation. The end result is multi-organ failure as lipid is deposited in the liver and kidneys.
Risk factors of hyperlipaemia in donkeys
The following risk factors have been identified in relation to hyperlipaemia in donkeys (Grove, 2008):
- Body condition: the prevalence of the disease is in fat and obese animals due to higher body-fat reserves and increased insulin resistance
- Stress: donkeys are more susceptible to hyperlipaemia in times of stress, such as during transportation and in unknown environments (eg being admitted to an equine hospital)
- Age: older animals are more prone to the disease
- Sex: females are more likely to develop the disease than males
- Late pregnancy and early lactation: the additional energy demand during these times increases the risks of developing hyperlipaemia
- Cushing’s syndrome: cortisol antagonises the effect of insulin, which allows body fat to be readily mobilised
- Laminitis: primary hyperlipaemia can be seen in laminitic animals due to the association with insulin resistance
- Concurrent disease: any disease that puts the animal in a negative energy balance can cause hyperlipaemia
- Surgery: the starvation period before surgery, added to the possible period of inappetence that follows, increases the risk of the patient developing a secondary hyperlipaemia
It is worth mentioning that prolonged periods of starvation before an anaesthetic are not recommended in donkeys. Twelve hours should be sufficient, although many equine anaesthetists argue that preoperative starvation is unnecessary. At The Donkey Sanctuary, hard feed and hay are withheld overnight before an anaesthetic (Evans et al., 2021). The donkey is then removed from straw or grazing on the morning of the operation for elective procedures. Suckling foals should not be starved.
Early clinical signs of hyperlipaemia are often vague and easily missed. Due to the predisposition of donkeys to hyperlipaemia, any animal with one or more risk factors should be monitored closely by the RVN and, ideally, receive preventative treatment.
Due to the predisposition of donkeys to hyperlipaemia, any animal with one or more risk factors should be monitored closely
Clinical signs include, but are not limited to (Grove, 2008):
- Gut stasis with diagnostic mucus-covered, dry faecal balls
- Congested mucous membranes with delayed capillary refill time
Diagnosis of hyperlipaemia in donkeys
Diagnosis of hyperlipaemia is the responsibility of the veterinary surgeon; however, RVNs can help by performing diagnostic tests when directed to do so and reporting the results.
Hyperlipaemia should be suspected in any inappetent and/or sick donkey. A blood sample should be taken to measure serum triglycerides. Grossly cloudy serum or plasma may be obvious, which enables prompt treatment before knowledge of an exact value for triglycerides (Evans et al., 2021). The Donkey Sanctuary’s normal range for serum triglycerides is 0.6 to 2.8mmol/l (53.4 to 249.2mg/dl) (Evans et al., 2021).
Liver parameters may also be elevated, although it can be difficult to determine whether this is a cause or effect, as high circulating levels of triglycerides can lead to the development of fatty liver disease. Other biochemical and/or haematological abnormalities may give an indication of the primary disease process or the development of pancreatitis (Evans et al., 2021).
Treatment of hyperlipaemia in donkeys
A comprehensive guide to the treatment of hyperlipaemia is beyond the scope of this article. However, the basic principles include (Grove, 2008):
- Treat any underlying disease
- Fluid therapy: maintaining circulating volume, correcting electrolyte imbalances and restoring acid/base balance
- Symptomatic therapy with non-steroidal anti-inflammatory drugs (NSAIDs), analgesics, anti-ulcer medication, multivitamins, anabolics and antibiotics
- Nutritional support to maintain a positive energy balance
Restoration of a positive energy balance is of utmost importance in cases of hyperlipaemia in donkeys. Pelleted high-fibre feeds or a ground oat instant breakfast cereal (eg Ready Brek 1.5MJ/100g) can be mixed with water, electrolytes and glucose and administered two to three times a day through a small-bore nasogastric tube (Evans et al., 2021). Pre- and probiotics can also be added.
Restoration of a positive energy balance is of utmost importance in cases of hyperlipaemia in donkeys
In some cases, a combination of enteral feeding and intravenous fluids provides the best outcome. In more severe cases of hyperlipaemia, donkeys have the best chance of recovery if hospitalised and parenteral nutrition is administered. Parenteral nutrition should be considered when the donkey does not significantly improve after 48 hours. Maintaining some voluntary food intake improves the prognosis (Evans et al., 2021).
Recommended foodstuffs to use to tempt an inappetent donkey to eat are (Evans et al., 2021):
- Yeast extracts
- Dried/fresh mint
- Bananas, including the skin
- Ginger biscuits
- Sugar beet pulp
If appropriate, the donkey and their companion/s could be walked out to browse in a hedgerow. Shrubs and branches could also be collected and fed in the stable to try to encourage some interest in eating.
Drug metabolism and pain relief
Although the prescription and dosing of medication is the responsibility of the veterinary surgeon, an RVN should be aware of the differences in drug metabolism between donkeys and horses.
Donkeys eliminate phenylbutazone much faster than horses. It has therefore been suggested that in order to achieve effective analgesia in donkeys, higher doses and shorter dosing intervals of phenylbutazone are required.
As donkeys are stoic and do not exhibit signs of pain as readily as horses, analgesic drugs must be considered very carefully. Drug selection and doses should be prescribed and administered with this in mind.
A donkey-specific pain scoring system should be used to monitor donkeys when in the hospital.
Mortality rates of 60 to 90 percent have been reported (Grove, 2008). Prognosis improves if the syndrome is detected in its early stages and prompt action is taken. This highlights the importance of the RVN carefully monitoring donkeys for signs of hyperlipaemia.
Prevention of hyperlipaemia in donkeys
Prevention is certainly better than cure when it comes to hyperlipaemia in donkeys – and this is an area where the RVN can really make a difference with careful monitoring and swift action:
- If any donkey shows inappetence, a blood sample should be taken and analysed for hyperlipidaemia (Grove, 2008)
- Reducing stress is also an important factor for an RVN to consider with patients coming into the hospital. Donkey companions should be welcomed and catered for. Plenty of “TLC” should be given
- If a donkey needs to lose weight, the RVN should make sure that this is done safely and slowly
- Strict monitoring procedures should be in place for donkeys starved for a general anaesthetic
- Every effort should be made by the RVN to encourage the patient to eat after the surgery once it is safe to do so
RVNs dealing with sick donkeys must be able to recognise the clinical signs of hyperlipaemia. Donkey-specific protocols should be put in place and adhered to in each equine practice. By following protocols specific to donkeys, the RVN can ensure that these patients receive individualised, species-specific nursing care and therefore have an optimum chance of recovery.
By following protocols specific to donkeys, [veterinary nurses] can ensure that these patients receive individualised, species-specific nursing care and therefore have an optimum chance of recovery