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And what you can do about it.

How do mud fever and Sallenders & Mallenders develop?

Mud fever is an inflammatory skin condition in the fetlock area. It can be oozing or dry and crusty, ranging from small, coin-sized patches to extensive areas affecting the entire cannon bone. If these symptoms appear on the back of the knees (carpal joints) on the front legs, it is referred to as Mallenders. When they occur on the front of the hocks on the hind legs, it is known as Sallenders.

Sallenders & Mallenders primarily affects horses with heavy feathering, such as draft breeds, Friesians, Cobs, etc. Mud fever can occur in all horses; however, those with heavy feathering are particularly prone to it. Greasy, waxy deposits on the front of the cannon bone, without involvement of the fetlock area, are not mud fever but are often similarly linked to metabolic issues. Many horse owners are familiar with the problem of mud fever, especially in winter, and try to combat it by applying various ointments.

Causes of mud fever or Sallenders & Mallenders in modern facilities

In the past, the main causes of mud fever were poor hygiene conditions, such as deep litter bedding and uncleaned paddocks. In these environments, bacteria and fungi could attack the skin and lead to inflammation.

A draught horse is standing in the muddy paddock next to a tree.
© Photogrevy / Adobe Stock

Poor hygiene is usually no longer the cause today

These conditions are now rarely found; as a rule, stables and barns are mucked out daily, and paddocks and pastures are cleared of droppings.

The skin is normally well protected

Nevertheless, horses still develop mud fever, especially in winter. This is often blamed on the muddy turnout areas. However, mud alone is not a problem for healthy horse skin. A natural protective acid mantle and the skin flora – the bacteria living on the skin – protect it from such external influences.

Common cause: Overload of the kidneys

The underlying cause of mud fever is, in most cases, a metabolic issue. The skin is the body’s largest auxiliary kidney. When the kidneys are overloaded, the body tries to eliminate waste products through the skin. Studies have shown that this excretion via the sweat glands works similarly to urine production in the kidneys. According to Traditional Chinese Medicine, the feet are also considered auxiliary kidneys of the body. With mud fever, both aspects come together: the primary kidney problem manifests as skin issues around the hooves.

In winter, metabolic issues often manifest as mud fever or Sallenders & Mallenders

Mud fever is so common in winter because moisture and sand further irritate the skin, which is already weakened by the body’s attempt to eliminate waste products through it. Additionally, in Traditional Chinese Medicine, winter is considered the “kidney season”—a time when the kidneys are particularly vulnerable. Damp cold places extra strain on the kidneys. In addition, nutrient supply is often suboptimal in winter due to the lack of grazing. If haylage, insufficient hay, or poor-quality hay is fed, and exercise is reduced because pastures are closed, and winter turnout areas are small, metabolic issues are almost inevitable. While one horse may show symptoms like feacal water, another may develop thrush, and a third may suffer from increased susceptibility to infections, some horses develop mud fever or Sallenders & Mallenders. Same underlying cause – different symptoms.

Caution: Sugar puts strain on the kidneys

Draft horses, Cobs, Friesians, and other hardy native breeds are particularly sensitive to sugar. Sugar is increasingly present in horse feed, often in the form of molasses, hydrothermally processed grains such as extruded or flaked cereals, as well as in carrots, apple pomace, and other sweet feeds. Sugar raises blood glucose levels, but the horse’s metabolism is not designed to handle such spikes. Draft and native breeds, in particular, have greater difficulty lowering their blood sugar after such meals compared to warmbloods. Consistently elevated blood sugar levels put significant strain on the kidneys, as the blood becomes thicker and more viscous, making it harder for the kidneys to filter. This can lead to slowly progressing kidney insufficiency, which often goes undetected. Kidney damage typically only becomes visible in blood tests when approximately 70 percent of kidney function has already been lost.

Haylage creates an unsuitable environment in the gut

Haylage is also one of the feeds that place strain on the metabolism. It introduces an excessive amount of lactic acid bacteria into the digestive system, which lowers the pH value in the large intestine. As a result, the natural gut flora dies off, and lactic acid bacteria take over. However, these bacteria are not part of the horse’s natural gut flora. They are unable to efficiently break down cellulose and do not supply the body with important B vitamins and essential amino acids, as the natural gut flora would. Horses can develop a deficiency in activated vitamin B6, which is essential for detoxification processes in the liver. At the same time, the horse absorbs increased amounts of lactic acid from the gut. This lactic acid must be converted into glucose by the liver, a process that requires oxygen and places additional strain on the metabolism. While lactic acid bacteria are beneficial for human digestion, the horse’s metabolism is not designed to process them efficiently.

Consequence: Acidosis

A gradual acidification of the connective tissue and the space between the cells is the result. The blood pH remains normal because the kidneys mobilise all reserves to prevent any fluctuations. Their task is also to maintain a normal tissue pH level. To achieve this during acidosis, the kidneys retain more water, which is stored in the tissue and dilutes the acids there. The horses appear visually “round,” and the owner is pleased that their horse looks so well-fed. However, it is not muscle mass, but water that causes the tissue to swell. This, in turn, puts strain on the cardiovascular system, as much more pressure is required to flush sufficient lymph through the tissue and supply the cells. This strain results in high blood pressure in the kidneys, which gradually damages kidney tissue. The effects are not immediately visible but only become apparent years later.

Mud fever/Sallendar & Mallendar as early warning signs

Mud fever/Sallendar & Mallendar indicates that the kidneys are no longer able to perform their function adequately and urgently need relief.

Overload of the kidneys due to haylage feeding
© OKAPI GmbH

What can be done about it?

Check hygiene

For horses with mud fever/sallendars and/or mallendars, the first priority is, of course, to check the hygiene in the stable. Deep litter bedding, heavily soiled bedding, or uncleaned turnout areas must be cleaned, possibly disinfected, and kept tidy. Muddy paddocks that cannot be mucked out should be fitted with drainage and either gravelled or concreted, so that the horses have at least some dry and clean areas to stand on. Muddy paddocks with a low stocking density and therefore little manure are not a problem. However, a horse with acute mud fever/sallendars and/or mallendars should not be kept there initially but should be provided with a dry standing area whenever possible.

Optimise feeding

Secondly, feeding should be optimised. This includes providing a sufficient quantity of good, stalky hay to nourish the gut flora. Haylage and other silage products must be removed from the diet, as well as all feeds that are high in sugar, such as treats, carrots, apples, bread, heavily molassed compound feeds, pellets, and so on. Caution is also advised with hay cobs. As they must be soaked before feeding, the horses do not chew them properly and therefore produce too little acid-buffering saliva. This can also lead to acidification of the gastrointestinal tract.

Colon Restoration

Depending on what has been fed previously, gut restoration may be necessary to help re-balance the gut flora more quickly. Feel free to contact us for advice on how to support gut regeneration.

Test for Kryptopyrrolurie (KPU)

In cases of severe or long-standing mud fever/sallendars and/or mallendars, a test for Kryptopyrrolurie (KPU) should be carried out. This test is available through the laboratory www.sension.eu. If the result is positive, please contact us for advice on the necessary therapeutic measures.

Deacidification after feeding haylage

If haylage has been fed, a deacidification protocol is necessary. You can give OKAPI Prodic for 2–4 weeks – this binds acids in the gut, making it easier for the intestinal environment to stabilise.

Normalising blood sugar levels

If highly sugary feeds have been given, the horses should be gradually weaned off them and transitioned to a low-sugar diet, such as hay and OKAPI Seasonal Feeds. If insulin resistance or EMS is already present, the horse can be supported with OKAPI PankrEMS forte.

Supporting the kidneys

In any case, a protocol with OKAPI Spirulina (as powder or pellets) should be carried out. Spirulina algae binds toxins in the body, which are primarily excreted via the liver-bile-gut pathway, thereby relieving the kidneys. At the same time, the kidneys should be supported over a period of 12 weeks by alternating every two weeks between OKAPI Detox Herbs and OKAPI Grazing Herbs.

Skin regeneration

Feeding OKAPI Zinc Plus, OKAPI Sulphur Plus, and OKAPI Wild Seeds supports skin regeneration. Weeping mud fever/sallendar and/or mallendar, could be sprayed locally with colloidal silver for one week and then treated daily with EM-A. This prevents the colonisation of fungi and putrefactive bacteria. Dry mud fever/sallendars and/or mallendars, can be left alone, or – depending on its location and size – treated with a paraffin-free calendula ointment to prevent the skin from cracking and turning into weeping mud fever/sallendars and/or mallendars.

Long-term measures

Horses prone to mud fever/sallendars and/or mallendars should receive a course of OKAPI Detox Herbs, OKAPI Grazing Herbs, OKAPI Immuno Herbs, and OKAPI Bitter Herbs over the winter, alternating every two weeks. Alternatively, we recommend feeding OKAPI Seasonal Feeds to support the metabolism throughout the year and help ensure a mud fever/sallendars and/or mallendars free winter. In the long term, you should secure zinc supply with a OKAPI Mineral Balancer and occasionally feed OKAPI Wild Seeds to stimulate natural skin oil production.

Team Sanoanimal
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