Euthanasia and the Post-Mortem Examination

QUALITY OF LIFE AND THE DECISION TO EUTHANASE

Where the quality of life of a donkey is such that they are either ‘having more bad days than good’ or they are just having bad days, then euthanasia should be carried out without delay.

The assessment and monitoring of quality of life should be an exercise that includes owners, their vet and other professionals. Observation and recording are important elements that may show changes over time and will allow an informed discussion and provide justification for any advice given.

Templates for owner monitoring sheets and professional assessment records are available. These have been used by The Donkey Sanctuary and are recommended for this purpose.

The owner monitoring sheet allows the owner to observe and monitor specific parameters at regular intervals, which helps identify any deterioration. This may also help the owner to recognise the need to euthanase their donkey and to reach this decision together with their vet. It should be used to feed into the record sheet with the end-point assessment.

The Advancing Equine Scientific Excellence (AESE) UK End of Life project was a collaborative investigation of the factors affecting decision making surrounding the euthanasia of equids. The project reported that:

“Owners rely heavily on their vet for provision of information about quality of life and end of life planning and are happy for their vet to ask them to complete an end of life plan. When asked, owners said they would like information on costs and methods of euthanasia and carcass disposal. This included planning for euthanasia and carcass disposal. Lack of information does result in delays in euthanasia. When asked, owners said they would prefer to get information from direct discussion with their vet. However they would also like to have printed information available from their vet and will use trusted websites such as their veterinary practice to access information.”

PREPARING FOR EUTHANASIA

When preparing and planning for euthanasia it is important to consider: 

• The bonded companion: donkeys tend to form strong bonds with their companions and this is an essential consideration when planning for euthanasia. The weeks following euthanasia must also be part of the planning.
• The use of restraint: some donkeys have not been trained to the head collar and the owner may not be the best person to restrain the donkey at the time of euthanasia.

METHODS OF EUTHANASIA

Intravenous injection

The anatomy of the donkey makes intravenous injection challenging. Therefore it is advisable to use intravenous catheterisation to allow additonal administration of drugs without any delays.

Prior sedation may be indicated and may be administered orally or by injection.

However, it is important to note that xylazine must not be used to sedate prior to the use of secobarbital (Somulose) as violent convulsions may occur

Secobarbital sodium (quinalbarbitone sodium) 400 mg/ml combined with cinchocaine hydrochloride 25mg/ml (Somulose) and used at the standard equine dose (1ml/10kg) is effective in donkeys.

Most donkeys of about 10hh do not weigh more than 200kg so 20mls is normally the correct dose for a donkey of this size.

Other barbiturate based drugs should be used at standard equine doses.

Alternative options should only be employed when there is no alternative and only in the anaesthetised or unconscious donkey.

Humane destruction by shooting

It is essential to take account of legislation and best practice, including health and safety considerations, as in horses and ponies.

• The landmark for a head shot is slightly higher than in horses and ponies.
• The recommended site in the average donkey is 1—2cm above the intersection of two lines drawn between the base of the ear and the contralateral lateral canthus of the eye.

Captive Bolt

• It is important to take account of legislation and best practice, including health and safety considerations, as in horses and ponies.
• Use of the captive bolt may be effective in skilled hands and it is compulsory to carry out pithing or rapid exsanguination after its use.

THE COMPANION AND BEREAVEMENT

Donkeys tend to form strong bonds with their companions and bereavement management is an important part of planning for euthanasia.

This should be considered in the decision about when and where the euthanasia is carried out.

The potential distress to the companion donkey and the subsequent risk of developing hyperlipaemia can be reduced. It is important to discuss this with the owner and put a plan in place to limit distress as far as practical.

• The companion donkey should be allowed to ‘come to terms’ with the death of their companion by leaving the body of the euthanased donkey in an accessible location. This may cause distress to the owner.
• The body should be left with the companion until the companion loses interest. This may take several minutes or several hours.
• The risk of bereavement associated hyperlipaemia remains high for at least three weeks after the loss of a bonded companion, particularly if the bereaved donkey is now living alone.
• It may be advisable to take a blood sample from the surviving donkey to assess triglyceride levels if there is any concern during the period up to three weeks after the event.
• The risk of hyperlipaemia can be reduced by increased interaction on the part of the carer and vigilant monitoring for any dullness or other behavioural change.
• The appetite should be monitored carefully and any sign of a reduction in appetite will require immediate attention.

• Some owners may be keen to obtain a new donkey immediately but this can be yet another stressor for the surviving donkey. It may be better that the introduction of a new companion should be delayed for two to three weeks.
• It may be difficult to source a healthy older donkey but the owner should be advised that the introduction of a young, energetic donkey to a frail geriatric would not be in the best welfare interests of either animal.
• Where two bonded donkeys are both frail geriatrics it may be that euthanasia of both is indicated and would represent a sound welfare outcome. Euthanasia of both would also be indicated if the surviving donkey is blind and has relied upon its companion for guidance.

THE POST-MORTEM EXAMINATION

Information from the post-mortem examination can:

• help detect the reason why treatment has been unsuccessful in some cases
• provide a definitive diagnosis
• provide evidence for cases, such as prosecution for failure to comply with animal welfare legislation
• aid research, for example by identifying and describing new conditions and infectious agents
• contribute to public health by detecting and preventing risks from zoonoses
• provide health protection by identifying contagious, rapidly transmitted infectious disease and enabling advice about best biosecurity practice
• provide valuable material for educational purposes such as training veterinary students and CPD for veterinary surgeons.

The Donkey Sanctuary would always encourage clinicians to share or publish information gained so that we can expand our evidence based knowledge.

Post-mortem examination may include weighing the donkey and should include taking any other measurements, such as girth measurement and body score. The body condition score should be assessed using the donkey specific chart.

The donkey will often have fibrosed adipose deposits in the crest and dorsally over the ribs, which can persist despite extreme weight loss and emaciation. Body condition score can be judged by assessing the fat cover over the lateral aspects of the ribs. Other condition-scoring landmarks, such as spinous processes, may be altered by post-mortem changes such as rigor. The muscle cover at any body condition score is likely to be less in a geriatric donkey than in a young fit working animal with comparable adipose deposits.

Typically, retroperitoneal fat in the ventral abdomen will be several centimetres thick in a donkey of condition score 3 to 4, and as much as 10cm in donkeys of body condition score 5. In the latter case there may also be considerable retroperitoneal adipose tissue around the kidneys and pelvic viscera.

Assessing the neck crest fat deposits is important in donkeys, because some donkeys retain the fat in the neck crest even after losing weight.

When examining the stomach, inspect the gastric mucosa for ulceration. Most pathology will affect the non-glandular mucosa adjacent to the margo plicatus, the border between glandular and non-glandular parts of the stomach.

The favoured site of tapeworm (Anoplocephala perfoliata) attachment in the horse and pony is the ileo-caecal junction, although in donkeys in the UK most tapeworms are found within the caecum at post-mortem examination.

The donkey caecum is similar to that of the horse and pony, but with a shorter, rounder apex. The contents are generally very watery, with small amounts of fibre. Inspection of the mucosal wall will often reveal vacated cysts of the larval stages of the cyathostomins (1mm opaque white circles and semi-spheres). Some paler cysts may contain larvae just visible to the naked eye as tiny black dots. When large numbers of larvae are entering or leaving the mucosa, considerable ulceration and inflammation can occur, resulting in marked oedema. If mucosa without oedema is stripped and examined with a back-light under a dissecting microscope, the larvae can be visualised and counted so that a larval density can be calculated.

The presence of active parasitic arteritis due to Strongylus vulgarus is probably quite rare in the UK and other similar countries, due to widespread use of modern anthelmintics. In other environments parasitic arteritis may be more common. Once developed, these lesions of the cranial mesenteric artery do not resolve rapidly. Adult pinworm (Oxyuris equi) can be found in the right dorsal colon, with tens of adults identified in severe infections.

The hepatic biliary tree should be opened and inspected for adult flukes (Fasciola hepatica).

Hydatid cysts, the larval form of the tapeworm Echinococcus granulosus, are uncommonly found within the hepatic and lung parenchyma of donkeys, although when found, it is more common in the liver. Clinical disease occurs only when more than 75% of the hepatic parenchyma is replaced by hydatid cysts.

Note that hydatidosis is a potential zoonotic disease. Therefore, do not cut into the hydatid cysts without the appropriate personal protective equipment: mask, visor, gloves and gown.

Despite pre-mortem anorexia, it is not uncommon for the stomach to contain substantial amounts of ingesta. This should be distinguished from gastric impaction, a condition usually associated with chronic hepatic disease in the donkey. In these cases, the stomach will be massively distended, often to the point of rupture, with very heavy, dry ingesta.

On opening the larynx and trachea, the cartilages should be examined. Tracheal collapse is common in the donkey, with tracheal rings appearing misshapen, overlapping or flattened. The lumen of the respiratory tree may contain some frothy fluid but should be free of muco-purulent exudates or parasites (Dictyocaulus arnfieldii). D. arnfieldii adults may reside deep in the respiratory tree and therefore thorough opening and examination of the bronchi is required.

In female donkeys the ovaries are located near the kidneys within the caudal abdomen. During anoestrus the ovaries are a little larger than big kidney beans. During the breeding season the ovaries will be the size of quail eggs.

Asymptomatic granulosa cell tumours have not been reported in the donkey, although large, fluid-filled ‘cysts’ will occasionally be found that can be associated with colic. These are filled with sterile, dark, watery fluid and are likely to be follicles that failed to reach the ovulation fossa (anovulatory follicles). In some cases they can be football-size. Frequently, rupture of small vessels in the anovulatory follicles may lead to haemorrhage and secondary haemoabdomen as a consequence of a ruptured anovulatory follicle.

ANATOMICAL DIFFERENCES

Anatomical differences from horses and ponies may be viewed as adaptations to the donkey’s natural environment.

• The large ears are useful to receive communication from disparate groups and to aid in heat dissipation.
• The angled epiglottis, narrow nasal meatuses and expanded nasopharyngeal recess play a role in the production of the characteristic resonant bray of this species, which can carry across many kilometres.
• The bones of the head are much larger than in a comparably sized pony, with a very powerful jaw capable of grinding lignin-rich plants and shrubs.
• The maxillary sinus is divided into rostral and caudal compartments by a thin, incomplete bony septum, in contrast to the horse and pony which have a complete bony septum.
• The short neck and protruding manubrium support the heavy skull, leading to an increased thickness of the cutaneous coli muscle.
• The distal punctum of the nasolacrimal duct opens far dorsomedially within the nostril, well placed to avoid blockage with sand.
• The abdomen often appears to be more pendulous than in the horse and pony due to a high-fibre diet, lack of muscle tone and intraabdominal fat deposits.
• The sacrum of the horse is a relatively flat bone with five segments. The donkey’s sacrum also has five segments, but often the first coccygeal vertebra is fused to the sacrum with occlusion of the sacrococcygeal space.
• The donkey sacrum is curved dorsoventrally, directing the spinal canal ventrally in the caudal segments. The sacral spines point backwards and rapidly decrease in length caudally. The spinal canal slopes backward more steeply, to end at the third coccygeal vertebra. The spinal cord ends at the second sacral vertebral segment, whereas the dural sheath extends back to the first or second coccygeal vertebra.
• The coccygeal vertebrae are much better developed in donkeys than in horses, with the vertebral arches of the first three being complete and each having interarcuate ligaments.
• The first intercoccygeal space in the donkey is narrower than the second space. In horses the spinal cord ends at the junction of the first and second sacral vertebral segments and the dural envelope at the fourth sacral segment. The vertebral arches of the second and third coccygeal vertebrae of horses are incomplete, with an absence of any interarcuate ligaments.
• The vertebral formula for the donkey is C7, T18, L5, S5, Ca 15–17.
• The dorsal top line of the donkey, with its low withers, straight back and smooth, slow paces, has encouraged its use as a pack and draught animal rather than as an athlete of the equine world.
• The upright hooves and typically close limbs are suited for movement in difficult terrain, rather than for speed.
• The ergots of the donkey tend to be more prominent and suggestive of a vestigial foot pad. • Some male donkeys have teats on their sheath and have proportionately larger reproductive organs than horses.
• The anatomy of the cervix of the female donkey differs from that of the horse and pony, not only in size (being longer than the mare’s and smaller in diameter), but also in the existence of a large protrusion from the cervix into the vagina.
• There are dorsal and ventral folds in the vaginal region that impede passage to the cervix.