veterinary

Any donkey of 20 years of age or older is considered to be geriatric. While companion animals will form the mainstay of geriatric donkey patients, it is not uncommon to experience aged working donkeys overseas and the following comments may be equally applicable.

Conditions of geriatric donkeys are frequently overlooked not receive regular, thorough inspection. Veterinarians may be called upon in an emergency situation, or, ideally, annual veterinary checks may be in place as part of routine vaccination protocols. It is important that any associated paraprofessionals are also aware of care of the geriatric donkey, as farriers and dental technicians can play a vital role in alerting owners to any potential health problems.

Stoic in nature, the donkey’s inherent behavioural response is to avoid displaying pain, thus the true extent of a pathological condition may be easily missed; it is vital that a thorough clinical examination of the whole donkey takes place at every veterinary visit. Beneath the thick coat may lie an underweight or obese animal, or advanced skin disease. Respiratory and musculoskeletal conditions of the non-athletic donkey may not be apparent at rest until an advanced stage has been reached. Research from The Donkey Sanctuary has identified a high proportion of advanced dental disease and poor to no routine dental care in relinquished geriatric donkeys (unpublished data). Heavy endo- and ectoparasite burdens have been seen in geriatric donkeys at The Donkey Sanctuary.

Chronic laminitis is highly prevalent but frequently overlooked by owners. Classic weight shifting is less reported in donkeys, with subtle changes in gait the more frequent indicator; depressed demeanour, muscle wastage over the shoulders and a reluctance to walk, alongside external hoof changes, should all trigger a check for laminitis. Hoof radiography is strongly advised to aid diagnosis and assist with remedial farriery.

Testing for pituitary pars intermedia dysfunction (PPID) is advised in cases of chronic laminitis, particularly where changes in demeanour, muscle wastage, recurrent infections and high faecal worm egg counts are seen. The classic hirsutism and hyperhidrosis seen in horses is not commonly identified in the donkey. Presently, measurement of basal adrenocorticotropic hormone (ACTH) is advised as a diagnostic test. Use of the thyrotropin-releasing hormone (TRH) stimulation test may be advisable in equivocal cases, although donkey-specific reference ranges have not been validated. If PPID is diagnosed, therapeutic management with pergolide mesylate at standard equine doses is valid, although owners should be cautioned as to the potential for inappetence and secondary hyperlipaemia.

Osteoarthritis of the axial and appendicular skeleton is very common. Owners may notice little more than a reduction in ambulation of the donkey and deterioration in temperament on handling. An onset of reluctance to raise the limb for foot care may indicate pain of the limb joints. Farriers should be advised to keep the limb as low as possible during foot trimming sessions. A donkey that rarely lies down or rolls or has sores over the carpi or hocks is also a cause for concern. Management of the arthritic patient should involve careful weight control, access to flat pastures where possible, routine farriery, consideration of appropriate bedding material, and adequate analgesia. Appropriate analgesics include phenylbutazone 2.2 mg/kg bwt orally twice a day or carprofen 0.7–1.3 mg/kg bwt orally once a day. Firocoxib has been used, but to this author’s knowledge there are no published data relating to its use in donkeys. Paracetamol 20 mg/kg bwt orally twice a day has been used as short-term adjunctive analgesia in acute-on-chronic presentations of both osteoarthritis and laminitis. While gastric ulceration has been seen at postmortem examination, there have been no studies linking its occurrence with long-term NSAID administration in donkeys.

Weight loss is a common presentation of the geriatric donkey. Diagnostic work-up should follow the same principles as for other equines. Liver disease appears to be relatively prevalent in the geriatric weight loss case, with liver fibrosis not infrequently seen at post-mortem examination. A thorough dental examination is paramount in weight loss cases; significant and painful dental disease is often identified.

Conversely, obese geriatric companion donkeys are also frequently seen and pose a particular hyperlipaemia risk. The diet of the geriatric donkey should be adjusted to account for desired weight, seasonality, underlying health concerns and dental disease. Short-chop forage products may replace straw for donkeys with poor dental function. Poor dental function and failure to provide access to warm drinking water in colder months have been significantly associated with an increased incidence of impaction colic in geriatric donkeys [1]. Balancer products should be fed to reduce vitamin and mineral deficiencies.

Ocular lesions are often identified during routine clinical examinations of the geriatric donkey. Advanced cases of uveitis, non-ulcerative keratitis and glaucoma may be present despite little indication of pain, while cataract formation is seen regularly. Ocular conditions should be treated and monitored as for other equines, with particular emphasis to owners on the subtle clinical signs of pain in the donkey.

Interstitial pulmonary fibrosis appears relatively prevalent amongst geriatric donkeys presenting with respiratory disease. Disease is rarely recognised until advanced, and/or secondary bacterial pneumonia has increased the severity of clinical signs. The disease is invariably fatal, although over wideranging time periods. Ultrasonographic imaging and thoracic radiography can aid the diagnosis where the clinical signs raise suspicion of disease. Equine herpesvirus-5 has been isolated from bronchoalveolar lavage samples taken from donkeys with confirmed pulmonary fibrosis, and asinine herpes viruses have been detected in donkeys with interstitial pneumonia; however, the precise role of herpesviruses in donkey pulmonary fibrosis has not been definitively established [2,3].

Tracheal collapse has been identified in a high number of geriatric donkeys at post-mortem examination, such that age-related degeneration of the tracheal rings is thought to be common. Clinical signs are rarely seen unless advanced stenosis is present; the presence of concurrent respiratory disease may severely exacerbate clinical signs [4].

Quality of life assessments can play a vital role in monitoring geriatric donkeys with chronic conditions. Informal discussions will likely form a mainstay of regular consultations, while more formal recording sheets can assist owners to identify any decline in their donkey’s condition or highlight issues in the case of working donkeys.

Discussing and defining ‘end-of-life’ points is a critical part of this process. Awareness of pain scoring systems, including facial pain recognition scales, can provide useful information relating to the efficacy of analgesia and true severity of any chronic disease processes. Euthanasia of the donkey follows the same basic principles as for other equines. In the UK, Somulose® is the most commonly employed agent. It is essential to have a calm and experienced handler to assist with euthanasia. Due to the small size of the average donkey found in the UK, i.v. agents are frequently given off the needle, but use of an i.v. catheter is down to personal preference. Certain anatomical differences, namely, thicker skin and a prominent cutaneous colli muscle, can make jugular venepuncture more difficult than in horses. It is vital that any companion is allowed access to the deceased donkey until they lose interest in the body; this can take from minutes to hours. Owners should be advised to monitor closely the companion, as bereavement stress has been known to elicit hyperlipaemia. Further information can be found in The Clinical Companion of the Donkey [5].

References

1. R. Cox, C. J. Proudman, A. F. Trawford, F. A. Burden. (2007) Epidemiology of impaction colic in donkeys in the UK. BMC Veterinary Research 3, 1-11.
2. S. B. Kleiboeker, S. K. Schommer, P. J. Johnson, B. Ehlers, S. E. Turnquist, M. Boucher, J. M. Kreeger. (2002) Association of two newly recognized herpesviruses with interstitial pneumonia in donkeys (Equus asinus). Journal of Veterinary Diagnostic Investigation 14, 273-280.
3. A. K. Thiemann. (2012) Respiratory disease in the donkey. Equine Veterinary Journal 24, 469-478.
4. R. J. Powell, N. Du Toit, F. A. Burden, P. M. Dixon. (2010) Morphological study of tracheal shape in donkeys with and without tracheal obstruction. Equine Veterinary Journal 42, 136-141.
5. L. Evans, M. Crane. (2018) Euthanasia and the post-mortem examination. In: Clinical Companion of the Donkey, 1st edition, Troubador Publishing Ltd, Leicestershire. p 196.

Nutrition

A donkey foal should be weaned gradually from 6 months of age and able to graze and eat supplementary straw feed. Barley straw is the forage of choice for healthy donkeys with good dentition, as it is low in calorie content while high in fibre, which aids slow digestion and reduces the risk of gastric ulceration. Straw can also be supplemented with hay in cold weather or if extra energy is required. If excess calories are provided to young donkeys, there is a risk of development of orthopaedic conditions including flexor tendon contractures leading to club foot. To balance the high-fibre diet, a low-calorie vitamin/mineral balancer ration is needed until the foal is at least 2 years old or up to 3 years in the larger breeds of donkey. Top Spec provide a donkey specific forage balancer that is appropriate for young donkeys.

Donkeys have lower nutritional requirements compared with horses. Aim to feed 1.3–1.7% of bodyweight in dry matter, the amount dependent on the weather and the individual animal. The donkey’s body condition score should be measured at least four times a year, while weigh tapes and donkey weight normograms help to monitor for slow, steady weight gain. Weaning the foal can be a stressful time for the jenny, so she needs similar careful management and monitoring.

Castration

Castration is a valuable tool to reduce the population of unwanted donkeys and encourage responsible ownership. The optimum time to castrate a donkey is between 6 and 18 months, although some reports suggest that a jack may be sexually mature by 12 months. Donkeys castrated after 18 months are more likely to retain stallion-like behaviours, and to have complications from surgery due to extensive fat deposits in the scrotum, larger testicles and associated blood vessels. Ensure a thorough preoperative check; many donkeys will have had no veterinary contact until castration. Check for heart murmurs and subclinical lung disease. Discuss vaccination and worming programmes: at a minimum ensure tetanus protection. For most young donkeys, a field castration is adequate. Use a weigh tape or weight estimator to calculate weight. Take a qualified assistant vet or nurse to administer the anaesthetic and top-up doses, as the procedure takes longer than a standing castration. Owners are not suitable assistants. For field anaesthesia, remember to take equipment to protect the donkey’s face and eyes: towels, eye drops, padded head collar, etc.

The Donkey Sanctuary vets prefer to use a standard closed technique for castration of donkeys. The donkey is placed under general anaesthesia, and local anaesthesia is used in the testicle (5–10 mL depending on size). The upper hindlimb is held or roped out of the way. The area may need to be clipped as the scrotum is frequently covered with hair. In the young donkey there should be minimal swelling post-operatively; we use analgesia at donkey doses, for 3–5 days, and depocillin intramuscularly usually for 3 days. Encourage exercise daily; it is useful to cold hose the inguinal area to reduce swelling, avoiding saturating the wound with water. Monitor appetite, faecal output, and demeanour for a week post-surgery. Complications include haemorrhage and infection. If blood is dripping faster than 1 drop/second and not slowing, consider external pressure or re-anaesthetise to locate the source. Infection manifests as a slow-healing wound, discharge, and a painful thickening of the remaining cord tissue. Surgical investigation is often required. In cryptorchid donkeys the anti-Mullerian hormone (AMH) test is proven to detect retained testicular tissue. If this test is not available, a human chorionic gonadotrophin (hCG) stimulation test is required as the oestrone sulfate test is unreliable in donkeys.

Sedation and anaesthesia

Many young donkeys are not well handled, and we must provide good sedation in a welfare-friendly manner. Aim to keep bonded companions together to reduce stress, and consider oral or i.m. sedation if required before attempting i.v. access.

Young colts can have thick coats and a well-developed ventral neck muscle – clip the vein, elevate the head and aim for the jugular above or below the mid third of the neck. A catheter is needed to top up anaesthesia for castrations. Donkey skin is relatively thick so use a scalpel to nick the skin before inserting the catheter; using a bleb of local anaesthetic makes this easier. Typical equine doses of alpha-2 agonists work for donkeys, but be prepared to increase the dose if the donkey is stressed and do not induce anaesthesia until the head has dropped below the withers. Ketamine at a dose of 2.2–3 mg/kg is typically used together with diazepam at 0.1 mg/kg for induction. Multimodal analgesia is provided with the use of an NSAID, an opioid (typically butorphanol) and local analgesia. Donkeys metabolise ketamine faster than horses so be prepared to top up at timed 10-minute intervals with one-third of the induction dose.

If a triple drip is used for anaesthesia, use a recipe appropriate for donkeys, for example: 300 mL saline, 225 mL 10% guaphenesin, 225 mg xylazine and 900 mg ketamine. Avoid doses of guaphenesin above 150 mg/kg (1.5 mL/kg of 10% solution), as this can cause respiratory and cardiovascular depression. Decreased depth of anaesthesia is often preceded by increased rate and depth of respiration before movement occurs; monitor carefully.

Recovery from anaesthesia is usually good in donkeys, unless multiple ketamine top ups have been used. Be prepared to re-sedate with an alpha-2 agonist. A typical 180 kg donkey requires a size 16 mm endotracheal tube, but have a range of sizes between 14 and 18 mm available. Donkeys can be difficult to intubate due to the narrow epiglottis and caudally angled larynx.