Nutrition

Today’s domestic donkey and the world’s feral and semi feral donkey populations are descended from the African wild ass (Equus africanus) which evolved to live in semi-arid, often mountainous environments with mainly fibrous, poor quality, sparse vegetation available. 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. The donkey’s natural environment is in stark contrast to the temperate conditions and grassy plains of the horse’s ancestral home but shows why each species has evolved with differing dietary requirements.

The donkey’s superior ability to digest poor nutritional quality, fibrous plant material makes it well suited to working in areas where food is of poor quality or is limited, but this adaption often leads to obesity as well as increasing the risk of related disease such as laminitis in more sedentary companion donkeys, 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 overestimation of the nutrient requirements for maintenance and work.

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), and 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.

Protein requirements

Studies to establish the donkey’s requirements for protein are limited. However, research suggests:

• Donkey protein requirements are significantly lower than those of horses and ponies.

• Crude protein (CP) requirements are 40g CP/100kg bwt/day. In practice, for most mature healthy donkeys, protein requirements tend to be satisfied once 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. The following is advised as best practice:

• 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 to donkeys working in hot environments may be beneficial. Salt should be provided ad libitum, it is not recommended that it is added to other feed products.

FEEDING DONKEYS WITH GOOD DENTAL FUNCTION

Donkeys should be fed an appropriate diet to maintain good body condition while allowing them to satisfy their natural appetite and satisfy 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. Note that:

• Regular dental examinations are necessary to ascertain that the donkey is able to cope with a highly fibrous diet.

• Any transition to this type of diet must be made gradually to avoid the risk of a gastrointestinal impaction.

The most suitable way of providing donkeys with a high fibre, 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, studies carried out in a large population of donkeys showed no increased risk of impaction colic or gastric ulceration associated with such feeding practices in donkeys with good dental health. It is important to consider the donkey’s mobility, though, and to monitor feed and water intake closely.

The donkey should be fed with rations in a trickle-feeding manner throughout a 24-hour period to ensure sufficient chewing time throughout the day and night, as the donkey’s digestive system is adapted to a more or less continuous intake of food with high fibre content. Chewing promotes production of saliva, which acts as a lubricant and acts to neutralise the continuous production of acid in the stomach.

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 prevailing weather conditions. Safe logs and branches 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. For example:

• 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 may ‘sham eat’ for considerable periods of time; the animal appears to mouth and swallow food or may simply nudge it, but intakes nothing. Such behaviour is often a sign of a serious illness and should be investigated promptly. Hyperlipaemia must always be considered.

• Donkeys generally tolerate the presence of others well and may be fed successfully in a group.

However:

• 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.

FEEDING DONKEYS WITH COMPROMISED DENTAL FUNCTION

Dental abnormalities can not only impact a donkey’s behaviour and health but can significantly impact their diet, too. Mastication is essential to provide sufficient surface area for digestion of the fibrous plant material that donkeys have evolved to thrive on. As donkeys age a multitude of dental problems can occur resulting in pain and discomfort and/or an inability to chew and masticate food properly. Additionally, congenital disorders of the dentition in younger donkeys can lead to inadequate mastication. This can lead to quidding (food dropped from the mouth in a partially chewed state), gradual weight loss, impacted digesta in the digestive tract, halitosis, choke, associated depression and lethargy; or it may cause varying levels of inappetence predisposing donkeys to hyperlipaemia. Often, by the time symptoms are noticed by owners the dental disease has already reached an advanced stage. Early intervention and preventative care are therefore essential for donkeys of all ages to ensure oral comfort and to maximise masticatory ability by maintaining occlusal contact.

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.

Donkeys with only mild or correctable dental abnormalities (eg sharp points, hooks, broken or infected molars) that are being seen regularly by an equine dentist may require relatively few changes being made to their diet. As long as they are not quidding and choke is not a problem, they may still be able to be maintained on suitable long fibre forages. If needed, their ration can be supplemented with additional fibre feeds such as fibre pellets and unmolassed soaked sugar beet.

Donkeys with advanced dental disease or more severe dental abnormalities who are struggling to masticate long fibres effectively or those showing a reduction in food intake due to painful periodontal disease are likely to benefit from changes to their diet. Replacing long fibre forages with alternative fibre sources that can be chewed and digested more easily is likely to be beneficial. Short-chopped fibre products designed specifically for equines are ideal and can be fed as complete long fibre forage replacers at normal DMI requirements (1.3–1.7% bodyweight/day). Products should be chopped to a consistent short length and should not be too stalky in texture as they may be too difficult for donkeys with severe dental problems to grind.

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, however, 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 increase the risk of impaction colic when used as donkey bedding.

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 its quality of 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.

HYPERLIPAEMIA

Donkeys that have compromised dental function due to pain, discomfort or an inability to masticate food properly may show varying levels of inappetence, which can predispose them to the complex metabolic condition hyperlipaemia. This condition is triggered in response to a negative energy balance (where more energy is being used up than taken in), resulting in mobilisation of body fat stores to try and continue fuelling the body’s essential organs. Free fatty acids are circulated to the liver to be converted to glucose for use by the body. In a fasting state this would be a normal response. However, the problem with donkeys, ponies and small miniature horses is that they are not able to efficiently turn off the fat release so the blood soon fills up with excess fat in circulation, resulting in fatty infiltration of organs such as the liver, pancreas and kidneys. This can cause the organs to degenerate, leading to irreversible organ damage and ultimately death of the animal.

Hyperlipaemia is unlikely to occur in the absence of a predisposing risk factor and in most cases will be triggered by a specific event which tips the donkey into a negative energy balance. Hyperlipaemia may be either primary or secondary depending on whether the trigger factor is the presence of a primary stressor such as pain, loss of a companion, sudden dietary change, transport, social mixing, bad weather or sudden weight loss, or is secondary to an underlying disease such as colic, colitis, dental disease or parasitism.

As there is often a delay between the trigger factor and manifestation of clinical signs of hyperlipaemia, it is important to identify any stressors that may have occurred in the preceding few weeks. The general suitability of the diet and bedding should also be assessed. Paper bedding and feeding cereal grain based feeds have both been found to be risk factors for hyperlipaemia in donkeys.

Clinical signs are often non-specific but may include:

• dullness

• anorexia/reduced appetite

• reduced gut motility/ileus

• reduced faecal output – dry, mucous covered faeces

• halitosis.

Nutrition plays a key role in the treatment of hyperlipaemia along with the treatment of any underlying conditions. The main aim is to reverse the negative energy balance before the fat released into the bloodstream has time to cause organ failure.

Mild hyperlipaemia cases in which animals have some voluntary appetite and no evidence of major secondary disease may be treatable in a home environment by means of enteral feeding. More severe cases are likely to need treating in a hospital environment where the companion(s) should accompany the patient in order to limit any additional stress from separation and to encourage appetite. While the exact energy requirements of sick donkeys are not known, an estimate of 60–100kJ/kg bwt/day is thought to be a reasonable target for the nutritional management of hyperlipaemia cases.

Appetite can be stimulated by offering the donkey:

• treats such as chopped apples, grated carrots, bananas (particularly the skin) and mints

• cut brambles, or allowing the donkey to browse in hedgerows – this can be effective in mild cases and during the recovery period

• flavour enhancers such as peppermint cordial, dried or fresh mint, ginger and fruit juices such as cherry, apple and carrot.

Rapid intervention and veterinary involvement is essential to treating this acutely life-threatening condition.

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 long- standing 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.