Anaesthesia and analgesia of the donkey and the mule

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.     

Pharmacology and therapeutics in donkeys

Therapeutics are often administered to donkeys based on dosage and intervals recommended for horses because very few drugs have donkey‐specific label indications. Yet differences between donkeys and horses in drug distribution, metabolism and elimination have been noted for most therapeutic agents studied. These differences can be partially explained by the donkey's unique physiology. Since their ancestors evolved in a desert environment, the modern donkey exhibits qualities that allow them to tolerate dehydration better than the horse and recover more quickly from its effects. Fluid balance and body water compartment partitioning differ from the horse and may have implications regarding drug distribution. Since donkeys are preferential browsers, differences in diet may have influenced evolutionary differences in metabolic disposition of drugs. It is important to acknowledge these differences when designing dose regimes for donkeys based on horse protocols in order to avoid either lack of efficacy or toxicity.     

Osteosarcoma of the proximal radius in a donkey

A mature donkey was presented for evaluation of a forelimb lameness and presence of a large mass on the left forelimb distal to the elbow joint. Clinical examination, radiographs and cytological examination of ultrasound‐guided fine needle aspirates of the mass led to a presumptive diagnosis of osteosarcoma. The donkey was subsequently subjected to euthanasia. Post mortem examination confirmed the diagnosis of osteosarcoma in the proximal radius with expansion of the mass through the ulnar cortex and metastases to liver and regional lymph nodes, areas of metastasis previously unreported in the equine literature.     

A comparative study of xylazine-induced mechanical hypoalgesia in donkeys and horses

ObjectiveTo compare the effects of xylazine on mechanical nociceptive thresholds in donkeys and horses.Study designRandomized, controlled, crossover, Latin-square, operator-blinded design.AnimalsSix 3.1 ± 0.89 year old standard donkeys weighing 145.0 ± 30.5 kg and six 9.6 ± 4.4 year old Thoroughbred horses weighing 456.0 ± 69.0 kg.MethodsEach animal received one of four doses of xylazine (0.5, 0.7, 0.9, and 1.1 mg kg^?1), or acepromazine (0.05 mg kg^?1) or saline solution (0.9%) intravenously and mechanical nociceptive thresholds were assessed over 90 minutes. The areas under the threshold change versus time curve values for 60 minutes (AUC_0-60) post-drug administration were used to compare the effect of treatment. A 1-week interval was allowed between successive trials on each animal.ResultsAll doses of xylazine, but not acepromazine or saline, increased mechanical thresholds for up to 60 minutes. Xylazine-induced hypoalgesia was dose-dependent and corresponding AUC_0-60 values for each treatment were not significantly different between donkeys and horses (p≥ 0.0697).ConclusionThe hypoalgesic effects of xylazine at four different doses were not different between donkeys and horses.Clinical relevanceXylazine induced a similar degree of mechanical hypoalgesia in donkeys and horses suggesting that similar doses are needed for both species with regard to analgesia.     

Common helminth infections of donkeys and their control in temperate regions

Roundworms and flatworms that affect donkeys can cause disease. All common helminth parasites that affect horses also infect donkeys, so animals that co‐graze can act as a source of infection for either species. Of the gastrointestinal nematodes, those belonging to the cyathostomin (small strongyle) group are the most problematic in UK donkeys. Most grazing animals are exposed to these parasites and some animals will be infected all of their lives. Control is threatened by anthelmintic resistance: resistance to all 3 available anthelmintic classes has now been recorded in UK donkeys. The lungworm, Dictyocaulus arnfieldi, is also problematical, particularly when donkeys co‐graze with horses. Mature horses are not permissive hosts to the full life cycle of this parasite, but develop clinical signs on infection. In contrast, donkeys are permissive hosts without displaying overt clinical signs and act as a source of infection to co‐grazing horses. Donkeys are also susceptible to the fluke, Fasciola hepatica. This flatworm can be transmitted, via snails and the environment, from ruminants. As with cyathostomins, anthelmintic resistance is increasing in fluke populations in the UK. A number of the anthelmintic products available for horses do not have a licence for use in donkeys, and this complicates the design of parasite control programmes. As no new equine anthelmintic classes appear to be near market, it is important that the efficacy of currently effective drugs is maintained. It is important that strategies are used that attempt to preserve anthelmintic efficacy. These strategies should be based on the concept that the proportion of worms in a population not exposed to anthelmintic at each treatment act as a source of ‘refugia’. The latter is an important factor in the rate at which resistance develops. Thus, it is imperative that parasite control programmes take into account the need to balance therapy to control helminth‐associated disease with the requirement to preserve anthelmintic effectiveness.     

Reference intervals for biochemical and haematological parameters in mature domestic donkeys (Equus asinus) in the UK

Reference intervals (RIs) for haematology and serum biochemistry for donkeys in a temperate climate have been previously published using blood sample results from the resident population of a large donkey shelter in the UK. Periodic review of reference intervals is recommended to ensure their applicability to the patient population and changes in laboratory methods and technologies. The current study aimed to revise the previously published haematology and serum biochemistry values for the adult domestic donkey (Equus asinus) in the UK in the light of a change in analytical equipment at the Donkey Sanctuary laboratory, but also to refine the demography of the sample population with respect to age, physiology and clinical history. Clinical pathology results from 138 clinically healthy mature (4–24 years inclusive) female and castrated male donkeys selected from the resident population of the Donkey Sanctuary, were analysed retrospectively. The animals were blood sampled during the period February 2008 to June 2011 as part of a routine health screen prior to rehoming. Results for a total of 38 biochemical and haematological parameters were analysed including 3 previously unreferenced parameters in addition to those assessed in the previous study. The new reference intervals and median values show very poor transferability with recently derived reference intervals for non‐Thoroughbred horses and only limited transferability with reference intervals previously published for donkeys in the UK. Of particular note is a marked reduction in the upper reference limit for triglycerides of 2.8 mmol/l (from 4.3 mmol/l) since this parameter is used to decide when donkeys are at risk of developing hyperlipaemia. This study demonstrates the value of intermittent review of reference intervals and refinement of study populations. Notwithstanding the caution with which reference interval data from different laboratories should be compared, the lack of transferability of results between donkeys and horses highlights the importance of use of species‐appropriate reference intervals for clinical decision‐making.     

Chemical restraint-reversal with medetomidine and atipamezole in veterinary small animal practice: a survey on the opinions of the dog owners and veterinarians.

The opinions of animal owners and practising veterinarians concerning a new restraint-reversal medication (medetomidine-atipamezole) for dogs were obtained by two questionnaires in connection with a clinical study. Four alternative answers to each statement question scored as "completely agree", "somewhat agree", "somewhat disagree" and "completely disagree". The questionnaires were completed by 21 veterinarians and 245 dog owners. The overall response to the treatment was clearly positive. Both groups had a favourable attitude towards drug use with mean combined scores (from 1 to 4; 4 = most favourable) of 48.1 (max 56) for the dog owners and 39.2 (max 52) for the veterinarians. Only a little information was gained about the background of negative sentiments. Some pet owners (19%) opposed to medication on a priori grounds, some (26%) reacted strongly to the dizziness of their animals and some owners (21%) complained because of general anxiety before, during and after their pets were treated.     

泌乳驴的日粮蛋白水平对驴驹生长发育的影响

试验旨在研究泌乳驴的日粮蛋白水平对驴驹生长发育的影响.选取健康、体况良好的5岁龄、胎次(1.9±0.4)胎、体重(240±30)kg、泌乳日期(29±5)d的带驹德州三粉驴24头,分为3个处理组(H、M、L组),饲喂蛋白水平分别为13.18％、12.22％和11.34％的日粮.每个处理组4个重复,每个重复2头驴.正式试...     

Pack wounds of donkeys and mules in the Northern High Atlas and lowlands of Morocco

Reasons for performing study: Wounds are one of the primary welfare concerns of working equids and are often related to harness or load‐bearing packs. Objectives: To identify and quantify factors associated with the presence of pack wounds in donkeys and mules working in the wood trade in the Midelt (Northern High Atlas) region of Morocco, and to compare wounds of these donkeys and mules to those working in other trades. Methods: The study population comprised equids working in the Midelt region involved in the wood trade. Comparison populations were comprised of equids working in other trades, in the same region and in Khemmiset region (lowlands of Central Morocco). Wounds were numbered and scored according to their severity. Questionnaires were used to gather data from owners, and objective data regarding the animal, berdaa (back‐pack) and load were collected. Data were analysed using multilevel uniand multivariable regression models to allow for clustering of wound sites within an equid. Results: Analysis showed an overall pack wound prevalence of 54% (n = 80/147). The most common site was the withers. Equids working in the wood trade were at increased risk of suffering pack wounds. Equids in the lowland study population were at increased risk of developing pack wounds, and donkeys were at increased risk of suffering pack wounds compared to mules both overall and within the wood trade. Other factors affecting the prevalence of wounds included the cleanliness of the berdaa and the frequency and distances of work imposed on the equid. Conclusion: Pack wounds in donkeys and mules are common in the 2 study regions of Morocco and appear to be associated with work factors including the trade the equids work in, the frequency and distances of work imposed and cleanliness of the pack. Donkeys are more susceptible than mules to developing pack wounds. Potential relevance: These results allow recommendations to be made to owners of equids that may decrease the prevalence of wounds and, therefore, improve welfare and working capability of these equids. Research is required to identify reasons for regional difference in prevalence of pack wounds in equids not working in the wood trade.     

Recognition and quantification of pain in horses: A tutorial review

Pain management is dependent on the quality of the pain evaluation. Ideally, pain evaluation is objective, pain‐specific and easily incorporated into a busy equine clinic. This paper reviews the existing knowledge base regarding the identification and quantification of pain in horses. Behavioural indicators of pain in horses in the context of normal equine behaviour, as well as various physiological parameters potentially useful for pain evaluation, are discussed. Areas where knowledge is sparse are identified and a new equine pain scale based on results from all reviewed papers is proposed. Finally, the most important considerations in relation to the implementation of a pain scale in a hospital setting are discussed.     

Respiratory disease in the donkey

The donkey suffers from a similar range of respiratory diseases as the horse; however, there are a number of subtle variations, knowledge of which can influence the success of treatment. As an animal adapted to a semi‐arid terrain, there are variations in physiology, anatomy and disease susceptibility. The nonathletic nature of the donkey means that delayed presentation is common with many diseases and, while there may be enhanced resistance to some transboundary and parasitic diseases, there may be equal or increased severity of illness to some endemic diseases, e.g. equine influenza. Donkeys frequently live to geriatric ages and the clinician should be aware of the increased risk of conditions such as tracheal collapse, fibrosing pneumonia and neoplasia in this age group. As with any condition that causes stress and inappetance, respiratory disease in the donkey may be complicated by hyperlipaemia and good nursing care is an essential component of treatment.     

Comparison of sedation and mechanical antinociception induced by intravenous administration of acepromazine and four dose rates of dexmedetomidine in donkeys

Objective

To assess and compare the sedative and antinociceptive effects of four dosages of dexmedetomidine in donkeys.

Seminal parameters and field fertility of cryopreserved donkey jack semen after insemination of horse mares

Reasons for performing study: As mule production is often concentrated in remote areas of the world, a simplified semen cryopreservation protocol is required. Aim: To compare the seminal parameters of cryopreserved donkey semen in lactose‐EDTA and lactose‐yolk extenders and the fertility rates on horse mares. Methods: Trial 1: Sperm total and progressive motility, vigour (scale 0–5), morphology (major and minor defects) and plasma membrane integrity (HOST) were evaluated in 25 ejaculates from 5 donkey jacks immediately after collection (raw), after chilling to 5°C (chilled) and after freezing/thawing. The semen was mixed with skimmed‐milk extender, centrifuged, and then re‐suspended in lactose‐EDTA or lactose‐yolk extender. Semen was loaded into 0.5 ml straws and chilled to 5°C for 1 h, after which samples were either evaluated (chilled semen) or placed above liquid nitrogen for 20 min prior to immersion. Seminal parameters were evaluated by ANOVA and Tukey's test. Trial 2: Cryopreserved semen from 3 males was used to inseminate 53 mares at 60 oestrous cycles randomly assigned to lactose‐yolk (n = 30 cycles) or lactose‐EDTA (n = 30 cycles) extenders. Pregnancy diagnosis was performed 15 and 25 days post ovulation. The pregnancy rates were compared using Chi‐squared tests. Results: Trial 1: No significant differences were evident in any seminal parameters between extenders after either chilling or cryopreservation. Total and progressive motility were significantly (P<0.05) lower in cryopreserved semen than raw and chilled semen for both extenders. Trial 2: Pregnancy rates did not significantly differ between extenders (lactose‐EDTA extender 53.33 and 43.33%; lactose‐yolk 50.0 and 46.66% for Days 15 and 25 post ovulation, respectively). Conclusions: Cryopreservation of donkey semen using the simplified lactose‐yolk extender resulted in similar seminal parameters and fertility rates when compared to lactose‐EDTA extender. Potential relevance: Lactose‐yolk extender may be advocated as a simple, easy to prepare extender, for use in geographically isolated enterprises producing mules throughout the world.     

Morphological study of tracheal shape in donkeys with and without tracheal obstruction

Reason for performing study: There is limited information on the gross tracheal morphology of donkeys with or without tracheal abnormalities. Objectives: To: 1) examine the morphology of tracheas of donkeys with and without clinical and/or post mortem evidence of tracheal obstruction; 2) record the cross‐sectional dimensions and shapes of tracheal rings at fixed sites; and 3) document prevalence, sites and characteristics of detected tracheal abnormalities. Methods: The tracheas of 75, predominantly aged (median age 30 years, range 7–48 years) donkeys that died or were subjected to euthanasia on humane grounds were examined. Five had severe dyspnoea due to tracheal obstruction (with intercurrent lung disease in 3), while 7 had post mortem evidence of severe tracheal airway obstruction. Every 5th tracheal ring was dissected free and the inner and outer vertical and transverse dimensions and cross sectional areas were measured. Each dissected ring was photographed and the shape of the trachea was classified as normal or, in one of 6 abnormal grades, according to the type and degree of structural abnormality present. Results: The tracheas had a mean of 43 (range 34–50) tracheal rings that tended to be more oval in shape in the distal cervical region. Only 31.2% of rings examined had a circular to oval shape. Dorso‐ventral flattening was present in 0.9% of tracheal rings, dorsal ligament separation in 24.4%, slight cartilage deformity in 26.0%, moderate cartilage deformity in 10.4%, marked cartilage deformity in 1.9% and miscellaneous other abnormalities in 4.9% of tracheal rings. The 12 donkeys with ante or post mortem evidence of tracheal obstruction had significantly increased tracheal abnormality grade in comparison to the remaining donkeys. Conclusions and potential relevance: Structural tracheal abnormalities are present in most old donkeys, but generally do not cause clinical problems in these sedentary animals unless intercurrent pulmonary disease is present.