Clinicians familiar with anaesthetizing horses will find many basic similarities between the species, but knowledge of some of the differences with donkeys will ensure a better approach.
Laminitis is a relatively common, painful condition of donkeys, ponies and horses. The underlying principles of pathology, diagnosis and treatment are broadly similar, but there are features of donkey anatomy, behaviour and physiology that differ from the horse; understanding these will improve treatment outcomes (Thiemann et al, 2021).
A study of over 2500 donkeys in the UK, found a prevalence of 4% of donkeys presented with laminitis with 46% of cases acute and 54% chronic. This is likely to be an underestimate due to the high levels of obesity and poor detection of the disease.
Recognition of laminitis
Few donkeys in Europe work, most are companion equines. This often results in late detection of laminitis in this species. Typically, signs are subtle, and include altered posture, stiff or shuffling gait and lameness on turning. There may be increased digital pulses and pain to hoof testers. Many donkeys will just lie down, and some owners can misinterpret this as normal resting behaviour.
In chronic cases, there will be abnormal growth rings on the hoof, a flatter sole and, in severe cases upper limb muscle atrophy and flexor tendon breakdown.
Using the Donkey Facial and Donkey Composite pain score (Van Dierendock, et al 2020) enables clinicians to quantify donkey pain and monitor response to treatment and analgesia.
The anatomy of the donkey hoof varies from the horse- P3 sits further distal and there is typically 10mm “founder distance” as normal between the coronary band, and top of the extensor process. The frog tissue is further back on the distal border of P3, this makes use of a heart bar shoe inadvisable. A normal hoof should have at least 10mm sole depth. The external hoof wall is approximately 5° more upright than a horse, but the phalanges, pastern and dorsal hoof wall should align.
Radiographs of donkey hooves need interpreting using donkey parameters.
Obese donkeys suffer from Asinine Metabolic Syndrome (AMS) and donkeys with Body Condition Score >3 (scale 1-5) are at risk. Donkey specific BCS charts and weight nomograms are available (The Donkey Sanctuary, 2020a & 2020b) to assist with assessment. Basal insulin and karo lite testing can be used to confirm a diagnosis of AMS.
Elderly donkeys can develop PPID and, as in the horse, seasonally adjusted donkey specific reference ranges are available.
Treatment of laminitis
As in the horse, the basis of treatment consists of rest, analgesia, foot care and dietary adjustments. In the donkey acute pain and stress, or rapid change in diet may precipitate life- threatening hyperlipaemia (Burden et al, 2011). Ensure the donkey’s appetite and demeanour are closely monitored, and while it is appropriate to reduce the sugar content of any fibre being fed, a reduction in fibre or attempts to diet an obese donkey should be done in a gradual manner.
Donkeys metabolise all NSAIDs (except carprofen) faster than horses, and after a loading dose of 4.4mg/kg BID of phenylbutazone, long term use at 2.2mg/kg BID is considered safe with less risk of dorsal colon ulceration. Meloxicam has a short half- life in donkeys (6 hours) and there is little data on newer NSAIDS. Paracetamol is a useful adjunct at 20-25mg/kg BID. Miniature donkeys require TID dosing for adequate analgesia.
Digital hypothermia is well -tolerated by donkeys and can be useful in acute cases or as preventative in sepsis cases.
In acute cases foot support is best provided with a deep bed, and whole hoof padding or using a commercially available sole support.
Corrective farriery after an episode is an important part of rehabilitation of the hoof, and for chronic cases with flat soles the use of acrylic rim shoes may assist in providing comfort.
Medical support for underlying AMS or PPID is similar to in the horse. The Donkey Sanctuary has little experience yet with the use of levothyroxine to aid weight loss, or insulin lowering drugs such as ertuglifloxin. Pergolide for the reduction of ACTH is known to cause appetite suppression in some donkeys, so when used, the donkey needs careful monitoring.
Prevention of laminitis
Preventative medicine in donkeys is often poor (Barrio et al, 2020), and engaging with owners about correct nutrition, weight management and farrier care is a good strategy. The Donkey sanctuary provides an online resource “The Donkey Academy” with free courses for owners, vets and farriers to assist in this area, as well as fact sheets and handbooks: https://www.thedonkeysanctuary.org.uk/research/what-we-do/knowledge-and-advice/donkey-academy
Donkeys with good dentition cope well on a high fibre, low starch diet where straw provides the bulk of the forage, supplemented by a small amount of vitamin/mineral balancer (Burden et al, 2019). If dieting is needed, suitable mental stimulation helps with prevention of stereotypic behaviour developing (The Donkey Sanctuary, 2020c).
In many cases severe chronic laminitis is undetected and vets and owners can work together to understand the impact of this on Quality of life and End of life Decision-making. The stoic nature of donkeys can results in prolonged unacceptable suffering.
References
1) Thiemann, A. K., Buil, J.and Rickards, K.(2021). A review of laminitis in the donkey. Equine Veterinary Education. 34(10) 553-560. Available from: doi.org/10.1111/eve.13533
2) Van Dierendonck M.C., Burden, F.A. and Rickards, K. (2020). Monitoring acute pain in donkeys with the Equine Utrecht University Scale for Donkeys Composite Pain (EQUUS-DONKEY-COMPASS) and the Equine Utrecht University Scale for Donkey Facial Assessment of Pain (EQUUS-DONKEY-FAP) Animals.10(2) 354. Available from: doi.org/10.3390/ani10020354
3) The Donkey Sanctuary (2020a) Donkey Body Condition Score chart. Available from: https://www.thedonkeysanctuary.org.uk/research/sites/uk/files/2020-01/body-scoring-chart-revised-01-2020.pdf.
4) The Donkey Sanctuary (2020b) Donkey weight nomogram. Available from: https://www.thedonkeysanctuary.org.uk/research/sites/uk/files/2020-01/donkey-weight-estimator-chart-revised-january-2020.pdf
5) Burden, F. A., Du Toit, N., and Hazell-Smith, E. (2011). Hyperlipaemia in a population of aged donkeys: description, prevalence, and potential risk factors. Journal of Veterinary Internal Medicine. 25(6)1420-5.
6) Barrio, E., De Blas Giral, I., Thiemann, A. K. and Vasquez Bringas, F. J. (2020) Demography, preventative health care and reasons for relinquishment of donkeys to an equine charity. Equine Veterinary Journal. 53(2) 324-330. Available from: doi.org/10.1111/evj.13310
7) Burden, F. A. and Bell, N. (2019) Nutrition and Malnutrition of donkeys. Veterinary Clinics of North America Equine Practice 35(3) 469-479.
8) The Donkey Sanctuary (2020c). Environment Enrichment: The Donkey Sanctuary’s Guide to Enriching the Lives of Donkeys and Mules. Available at: https://view.pagetiger.com/EnvironmentalEnrichmentforDonkeys/EnvironmentEnrichmentfordonkeys [Accessed September 19 2020].
Laminitis is seen relatively frequently in first opinion equine practice and affects all breeds of horse, pony and donkey. Studies in the UK of companion donkeys gives a prevalence that approximately 4% of donkeys suffered a laminitic episode in the preceding 12 months, of which 54% were chronic cases and 46% acute.
While there are many similarities in the diagnosis, management and treatment of laminitis in donkeys and horses, knowledge of the species specific differences will provide better treatment for donkey patients. This presentation will cover how to recognise laminitis in the donkey, and the treatment and management of acute and chronic cases.
The number of donkeys and mules throughout the world is stable, and awareness of their use and concern for welfare, pain recognition and treatment are receiving increasing veterinary interest. Therefore, accurate information about anaesthesia and analgesia in donkeys and mules is important to ever more equine practitioners. Since donkeys are physiologically and pharmacologically different from horses, knowledge on species specific aspects of anaesthesia and analgesia are very important. Mules combine elements from both donkey and horse backgrounds, leading to great diversity in size, temperament and body type. Physiologically, they seem to resemble horses more than donkeys. This review highlights the current knowledge on various anaesthetic and analgesic approaches in donkeys and mules. There is still much information that is not available about donkeys; in many circumstances, the clinician must use available equine information to treat the patient, while monitoring carefully to observe for differences in response to therapy compared to the horse.