Nutrition

The domestic donkey is descended from the African wild ass that evolved to live in semi-arid, often mountainous environments with mainly fibrous, sparse vegetation of poor quality. To increase their potential source of food, donkeys have evolved to be browsers as well as grazers, with woody shrubs and trees being potential food sources when grasses and other low vegetation are not abundant.

Donkeys are trickle feeders; in their natural environment donkeys spend around 14–18 hours a day searching for plant material to graze on, or woody shrubs and trees to browse on, while covering large distances (up to 20–30km/day) often over difficult rocky terrain. Donkeys have a superior digestive efficiency compared to horses and ponies when digesting highly fibrous forages such as straw, which makes them well suited to their natural environment. However, this adaptation can lead to obesity and increase the risk of related diseases such as laminitis in sedentary companion animals, especially when they are fed in the same way as a horse or pony. Obesity is also likely where donkeys are kept together with horses or ponies and are not fed and managed differently to their companions. An obese donkey is at high risk of developing serious health problems.

Key to the formulation of management and dietary plans is awareness that the requirements of donkeys are very different to those of horses and ponies. Failure to take this into consideration can lead to disease and behavioural issues in the donkey.

NUTRITIONAL REQUIREMENTS

Feeding recommendations for donkeys are often extrapolated from horse nutrition. However, this will often result in an over-estimation of the nutrient requirements for maintenance and work.

The donkey should be fed a diet high in fibre and low in energy and nonstructural carbohydrates. The majority of the diet is best supplied using straws or stover (the leaves and stalks of field crops such as corn, maize or sorghum) and supplemented with a variable proportion of moderate quality hay and/or grazing depending on what is available locally.

Energy requirements

Having an understanding of a donkey’s energy requirements is essential to help try and avoid under/over-feeding. Scientifically validated guidelines for digestible energy (DE) and dry matter intake (DMI) requirements for mature donkeys at maintenance have been established for donkeys kept in temperate and tropical climates as part of projects conducted in the UK and Mexico. Donkeys kept at maintenance levels were found to require between 80–95kj DE/kg body weight (bwt)/day (dependant on season). Their voluntary intake, when fed fibrous forages (barley straw or maize stover) supplemented with hay or grazing, was 1.3–1.7% daily of their bwt in dry matter (DM); as shown in the table below. This is considerably lower than the 2–2.5% intake recommended for ponies.

Companion and non-working donkeys require foodstuffs with low energy values so that they can eat enough to satisfy their natural appetite and the behavioural need to forage without becoming obese.

Working donkeys may require supplementary feeds, either due to the increased energy requirement or a lack of time to consume sufficient forage. Supplementary feeding should focus on higher quality fibre sources such as grass hay, alfalfa or grazing. Where concentrates are required they should be low in cereal grain content in order to avoid related health problems.

Protein requirements

Studies have been carried out to establish donkeys’ requirements for protein, but these are limited.

• Protein requirements are significantly lower than those of horses and ponies.
• Crude protein (CP) requirements are 40g CP/100kg bwt/day, whilst most mature healthy donkeys, protein requirements tend to be satisfied once digestible energy (DE) requirements are satisfied.
• Provision of additional quality protein to donkeys recovering from surgery or injury may improve recovery times; protein deficiency may limit tissue repair.
• Soya bean meal or alfalfa are excellent sources of digestible protein for convalescent donkeys.

Vitamin and mineral requirements

Donkey-specific vitamin and mineral requirements have not been established. However, the recommendations published for horses appear to provide optimal levels for donkeys and can be safely extrapolated.

• Provision of adequate vitamins and minerals is best achieved by allowing daily access to fresh grazing with an equine-specific mineral lick or vitamin and mineral supplement or balancer being provided where possible.
• Provision of sodium chloride may be beneficial for donkeys working in hot environments.
• Salt should be provided ad libitum, it is not recommended that it is added to other feed products.
• Care must be taken to balance calcium and phosphorus and to ensure sufficient levels of vitamin supplementation to animals fed primarily on dried forages.
• Donkeys maintained on dried forages or being fed high levels of oil (greater than 100ml) may be at risk of vitamin E deficiency, which could increase the risk of equine degenerative myeloencephalopathy or equine motor neurone disease, although no evidence is available.

THE NORMAL DIET

Donkeys should be fed an appropriate diet to maintain good body condition while allowing them to satisfy their natural appetite and the behavioural need to forage without becoming obese. A diet which is high in fibre and low in energy and non-structural carbohydrates (starches and sugars) is ideal, hence donkeys thrive on fibrous forages with a low energy density.

The most suitable way of providing a low energy diet is to offer straw where the cereal grain has been removed through harvesting (barley, oat or wheat) or stover (the leaves and stalks of field crops such as corn, maize or sorghum).

There may be a reluctance to feed straw to donkeys and mules due to concerns relating to colic and gastric ulcers. However, no increased risk of impaction colic or gastric ulceration associated with such feeding has been demonstrated in donkeys that have good dental health.

It is important to ensure:

• regular dental examinations and treatments are carried out, to ensure that the donkey is able to cope with a highly fibrous diet
• transition to this type of diet is gradual to avoid the risk of a gastrointestinal impaction
• donkeys with reduced mobility are monitored
• intake is monitored closely.

As the donkey’s digestive system is adapted to a more or less continuous intake of food with high fibre content, they should be fed with regular rations in a trickle-feeding manner throughout a 24-hour period to ensure sufficient chewing time throughout the day and night. Straw may need to be supplemented with variable proportions of coarse, low energy hay, haylage and/or grazing according to the donkey’s body condition, the time of year and the weather conditions. Logs and branches that are safe, and not toxic, should also be provided to satisfy the donkey’s natural browsing behaviours.

Where pasture is sparse or of poor quality, and particularly in warmer arid climates, free access to grazing may provide most of the donkey’s needs. However, donkeys fed solely on energy dense pasture often found in temperate climates may become obese or need to have their total dietary intake restricted to such an extent that they are at risk of developing gastric ulceration or stereotypies.
 

Although many donkeys can live on a diet of straw supplemented appropriately with grass and/or hay or haylage with supplemented vitamins and minerals as necessary, certain individuals, such as pregnant and lactating jennies, young growing donkeys, working donkeys or stallions kept for breeding purposes, may require supplementary feeds, either due to their increased energy requirement or a lack of time to consume sufficient forage. Such animals may need to be supplemented with higher energy, fibre or oil-based feeds such as alfalfa, unmolassed beet pulp or rice bran which should be given in small rations mixed with appropriate roughage such as an unmolassed short-chopped fibre.

Where cereal grains or molasses are included to increase the palatability or energy density of feeds, it is advised that combined starch and sugar levels (non-structural carbohydrates) do not exceed 15% and ideally should be <10%.

Donkey behaviour traits should always be considered when planning a donkey’s diet.

• Donkeys form strong bonds and it is often essential to have their companion at least within sight, otherwise one or both animals may refuse to eat despite their hunger.
• Donkeys generally tolerate the presence of others well and may be fed successfully in a group.
  • Dominant donkeys may bully other animals lower in the hierarchy and care should be taken to provide ample feeder space to prevent reduced intake by submissive animals.
  • Commonly donkeys are bullied at feed time by horses, ponies or mules, and may end up injured or unable to access enough feed to satisfy their requirements.
• Donkeys may ‘sham eat’ for considerable periods of time and such behaviour is often a sign of a serious illness and should be investigated promptly and hyperlipaemia must always be considered.

When 'sham eating' the animal appears to mouth and swallow food or may simply nudge it, but does not ingest any.

Equine feedstuffs based upon cereals or containing high levels of molasses are risk factors for the development of gastric ulcers and laminitis in donkeys and other equids and should be avoided.

The practice of intermittent ‘meal’ feeding is also to be discouraged because it is likely to produce peaks in insulin levels or increases in gastric pH. It has also been associated with hyperlipaemia, gastric ulcers and impaction colic in the donkey

The provision of an inappropriate diet can lead to the development of conditions such as laminitis, gastric ulceration, hyperlipaemia and fatty liver disease.

MONITORING THE DIET

Body condition scoring and monitoring of weight are an essential part of donkey husbandry but it is important to note that different techniques are needed to those used in horses and ponies. Donkeys lay down fat stores in more localised areas and have a different body shape than horses and ponies, and therefore it is essential that different techniques are used for body scoring donkeys.

The donkey has an angular frame alongside a pendulous abdomen, and is often incorrectly described as ‘pot bellied’. The pendulous abdomen may be due to increased retention of fibre within the gut and the related increased volume of the large intestine, abdominal fat, or, in sedentary animals, a slackness of the abdominal muscles.

Donkeys can have thick coats, especially in winter or when suffering from pituitary pars intermedia dysfunction (PPID), and appearances are often deceptive. Areas where fat is commonly deposited include the neck, shoulders, back, rump and the dorsal and lateral thorax.
 

Donkeys frequently develop a fatty crest which may fall over to one side of the neck. Once in situ these deposits rarely disappear, even with dieting, and should be ignored in a mature animal that is in otherwise good condition. Fat pads are common on the buttocks and the dorsal and lateral thorax, and donkeys often carry significant abdominal fat (often up to 8cm, but increasing up to 14cm in the obese donkey). When such fat pads are longstanding they may become calcified and therefore extremely hard. They will never be lost through dieting and should be ignored when condition scoring. Calcified fat pads are of clinical note; if the donkey is injured, a lack of blood supply to the area can promote the development of panniculitis, which may be difficult to treat.

FEEDING FOR COMMON CONDITIONS

The majority of donkeys manage very well on basic rations. However, there are cases which require specialist feeding.

Underweight donkeys

Before dietary changes can be made, a thorough clinical assessment should be carried out, including:

• observation of feeding behaviour and assessment of feeding and management practices (such as hobbling / tethering)
• a thorough dental examination
• blood sampling to assess the overall health of the donkey, with particular attention to liver and kidney function, PPID, Equine Metabolic Syndrome (EMS) and gastrointestinal issues, such as colitis and small intestinal malabsorption
• assessing the parasitic burden
• checking the workload and the availability of feedstuffs during working hours
• checking the level of preparation of feedstuffs; would the products provided benefit from being chopped, rolled, cracked or soaked to provide increased nutrient availability.

Working donkeys unable to access adequate feedstuffs are prone to a poor body condition score. In addition, such animals may have concurrent disease. Both working and companion donkeys with a low body condition score may have concurrent dental disease, liver disease or an issue with companions such as bullying or separation grief. A holistic approach to resolving all underlying causes is essential. When managing animals that require extra condition, it is important to encourage increased energy intake throughout the day by providing, for example, higher quantities of hay or a shortchopped fibre product.

Obesity

As in all species, obesity is a significant welfare problem and predisposes to a number of diseases.

Obese donkeys have higher insulin values, which are significantly associated with the occurrence of laminitis. Obesity and associated hyperinsulinaemia may increase the risk of a donkey developing laminitis, particularly that associated with grazing.

Dietary management of obese donkeys is challenging and requires ongoing veterinary input.

Inappropriate diet is often compounded by lack of exercise, issues with companions such as bullying or separation grief and EMS.

While obesity is uncommon in working donkeys, those that are worked infrequently or are kept for production purposes may also be at risk of obesity and related issues. A management approach to the obese donkey should include:

• a dental check to ensure that the donkey can be given a diet based on straw or stover
• an assessment of the donkey’s ability to exercise
• an appropriate blood sample.

As a result of information from these checks a plan can be put in place for the obese donkey.

• Donkeys with high triglycerides (higher than 2.8 mmol/l) should have an exercise programme initiated before dietary changes are made. Once levels fall within the normal range, dietary changes may be introduced.
• Dietary management for obese or laminitic animals or those with EMS that have healthy teeth should focus on straw with very limited grazing in temperate climates, and straw with limited hay when weather is cold (lower than 100C). If there are concerns about deficiency, proprietary vitamin, mineral and protein supplements may be fed in small quantities.

The plan must include management of the pasture if the donkey is grazing in temperate climates where grass will be nutritionally dense.

• Restrict intake by strip grazing, using a guide of less than 0.2 acre (0.08ha) per donkey of short cropped pasture which will benefit from rotation.
• Evidence suggests that fructan levels in grass may only rarely be sufficient to trigger ration-induced laminitis due to disrupted fermentation in the hind gut.
• High nonstructural carbohydrate (NSC); simple sugars, starch and fructan levels in grass may lead to increased insulin resistance and the development of endocrine-related laminitis.
• Maintain a healthy grass sward as nonstructural carbohydrate levels can be high in lush grass but also in frosty grass and grass stressed by drought or overgrazing.
• Management by reduction of time at grazing has been shown to have little effect upon the total dietary intake of donkeys and may lead to them spending every minute at pasture eating rather than exercising and carrying out social behaviours.
• Restriction of time at grazing is often followed by long periods of confinement which will exacerbate issues in the obese donkey.

In order to encourage donkeys to lose weight, they should be appropriately exercised wherever possible.

Donkeys should be condition scored and have their weight estimated monthly. Progress when dieting donkeys is slow, and perseverance is essential. It often takes weeks for the first weight to be lost. However, once this process begins, weight loss should be gradual. The aim should be to lose 2—3% of bodyweight monthly.

The inappetent donkey

Donkeys are particularly prone to developing hyperlipaemia.

Donkeys with some voluntary appetite

Research has shown that inappetence or anorexia, often accompanied by dullness or lethargy, are the most frequent presenting signs when dealing with sick donkeys. If a sick donkey has an appetite they should be given a diet that is similar to that normally provided and in a hospital situation straw would be the diet of choice.

Nutritional management of sick donkeys often focuses upon the need to stimulate the donkey’s appetite. However, although molasses and cereal grains can be used successfully in the short term, they can be detrimental in the long term.

Many donkeys can be tempted with fibrous equine feeds by adding tempters such as:

• mint cordial
• yeast extracts
• dried or fresh mint
• bananas, including the skin
• ginger, grated or in powder form
• carrots or apples, grated, juiced or chopped
• unmolassed beet pulp, soaked
• other locally available fruit or vegetables known to be safe for equines.

While nursing a sick donkey that is reluctant to eat, some tips include:

• tempt the animal to eat from the hand, because large buckets are often refused
• ensure the sick donkey’s companion is close by, even within a hospital setting
• do not underestimate the donkey’s natural instinct as a browser and a donkey with no interest in food may be tempted if led to a nearby hedgerow or scrub area to browse on brambles and herbs.

A dental examination should be carried out. Blood samples should be used to assess the overall health of the donkey, paying particular attention to triglyceride concentration and parameters relating to liver and kidney function, PPID and EMS.

Donkeys without voluntary appetite

When administering treatment by nasogastric tube or oral drenching, the potential for exacerbating or predisposing to hyperlipaemia through resultant stress must be balanced with the clinical needs of the patient.

When administering fluids by nasogastric tubing for more than a couple of days, provision of sufficient potassium should be ensured as it is rapidly excreted and insufficient levels may lead to ileus. Inclusion of 1g potassium chloride in every litre of fluids should be sufficient, alongside normal preparations.

Patients should be fed with a fibre rich product, such as a ground instant oat breakfast cereal. The addition of pre- and probiotics is beneficial. Consideration should be given to the administration of gastric protectants.

In hyperlipaemia cases parenteral nutrition should be considered and such treatment should begin promptly.

Dental disease

Dental disease is common in donkeys, particularly geriatrics, and this often leads to an inability to chew long fibre forages, causing gradual weight loss with associated depression and lethargy. In serious cases, dental pain can lead to a donkey becoming inappetent and predisposed to hyperlipaemia.

Examination of faeces can provide clues regarding the impact of dental pathologies on digestion, with excessive faecal fibre length (FFL) typically indicating that dental abnormalities are present.

It is essential to replace long fibre forages with alternative fibre sources that can be easily chewed and digested.

Short-chopped, straw-based products with energy levels of approximately 6.5–8MJ/kg dry matter and non-structural carbohydrate levels of less than 10% should suit most donkeys.
 

Chops can be fed from large tubs or troughs and should be trickle-fed throughout the day to ensure a constant source of fibre is available. Feeding of such products ad libitum may lead to gorging in the short term, although intake is often self-regulating after a few weeks. Even so, chops may be consumed more quickly and in greater quantities than long fibres, so regular offerings may be needed. In general, a donkey weighing 180kg will require 2.5–3kg of short chop per day. Unless the chop is a complete feed – e.g. contains the required levels of vitamins and minerals – a balancer, supplement or mineral lick will need to be provided to ensure the animal receives all the essential nutrients it needs.

The choice of bedding material used will also need to be given consideration, with a non-straw option generally most appropriate for donkeys with severe dental problems. There are many different options available but The Donkey Sanctuary would not advise the use of paper or cardboard bedding as we have found these to increase the risk of impaction colic when used as donkey bedding.

Donkeys that do not require such drastic changes in diet can be given small, frequent feeds of high fibre concentrates and unmolassed sugar beet pulp, alongside forage.

If a donkey has such severe dental problems that it cannot eat even chopped forages, then fibre pellets soaked in water to form a mash/gruel can be fed to normal DMI requirements but will need to be offered in small meals (no more than 1kg at a time) at regular intervals throughout the day. If such a diet is all a donkey can manage, then the quality of their life should be discussed with the owner, bearing in mind that a donkey’s normal behaviour would be to eat for up to 14–18 hours in a 24-hour period.

Laminitis

In the acute stages of laminitis it is essential to remove any contributory dietary issues. The donkey should be removed from pasture and given a high fibre, low non-structural carbohydrate (NSC) diet.

Note that:

• it is essential to maintain fibre intake as starvation of the donkey is likely to result in hyperlipaemia
• straw may be fed but it is essential to monitor gut motility and faecal output during periods of decreased mobility due to laminitis
• a short-chopped forage with an NSC level of less than 10% is ideal to maintain the animal in the short term
• hay may be fed but be aware that NSC levels in some hay is high and may be inappropriate.

Liver and kidney disease

Dietary management is a key component of a treatment plan for donkeys suffering from liver or kidney disease.

The donkey with liver disease needs a low protein diet resulting in reduced ammonia production. Such a diet, with less than 8% protein, can be met by grass, hay, straw and pasture. In addition:

• avoid alfalfa or cereal based feeds
• levels of fat within the diet should be controlled
• supplementary oil is discouraged
• short-chops, unmolassed beet pulp and high-fibre cubes are suitable where supplementary feeding is required.

The donkey with kidney disease should have a diet low in calcium and protein (less than 8%) and, where possible, should be maintained on hay and pasture.

In addition:

• avoid legumes such as alfalfa and clover containing high levels of protein and calcium
• if required, extra energy can be supplied in the form of high oil supplements
• feed balancers designed for native ponies are also useful in such cases.

PRE- AND POST-NATAL FEEDING

Nutrient requirements for pregnancy and lactation in the donkey have yet to be established and guidelines are extrapolated from data available for horses and ponies. 

• In the final trimester, the female donkey will have a greater energy requirement, and it is important to supply quality protein, vitamins and minerals as the foal grows. 
• In order to supply these nutrients, the energy density and quality of forages must be increased:
  • Gradually increase the hay portion of the diet until it constitutes the majority of the diet.
  • Use a supplement containing vitamins, minerals and protein, with low NSC levels as designed for small ponies, at 75% of the levels recommended for ponies of a similar size.
  • If good quality hay is not available, supplementation with alfalfa or unmolassed beet pulp is useful.
• During late pregnancy, digestive tract capacity will decrease, which may lead to the female donkey being unable to satisfy the energy requirements of herself and the foal, which may leave her predisposed to hyperlipaemia.
• A slight increase in condition before foaling is acceptable (body condition score 3.5) to allow for expected weight loss in the early stages of lactation.

While lactating, the female donkey should receive adequate, good quality pasture and hay.

• Supplementation with vitamin and mineral products, chopped alfalfa or high fibre concentrates may also be indicated.
• Hyperlipaemia is a concern in the lactating donkey. Owners should monitor appetite and ensure adequate feed is provided.

The foal should be allowed to pick at the dam’s feed in preparation for weaning.

• Generally, donkey foals are weaned at approximately six months old

• Foals should grow steadily and it is best practice to monitor the weight and condition of the foal every two weeks. If the rate of growth is too rapid, nutritional intake should be restricted, but with appropriate vitamin and mineral supplementation.
• If the foal is stunted, appropriate supplementary feeding will be necessary and expert advice should be sought in these situations.