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Yes, that’s possible.

Mud fever and its typical crusts in the creases of the fetlocks, or even higher up on the carpal or hock joints (mallenders/sallenders) is commonly associated with winter, muddy conditions, and wet feet.

Less-than-ideal living conditions, where horses are consistently standing in mud, particularly when mixed with faeces, can trigger mud fever. However, there are horses that have healthy feet during winter but develop crusts in the fetlock creases during the grazing period in summer.

The exact causes of this phenomenon have not been scientifically investigated, but it is unlikely to be solely due to persistent moisture and faecal bacteria, as long as the pastures are dry and spacious enough.

Mites have been considered as potential triggers since they can be found on the grass. However, not all horses on the same pasture are affected; only a few individuals show symptoms. This suggests that there may be something specific about these horses that attracts the mites, or perhaps mites are not involved at all.

Interestingly, the affected horses are often those that are prone to metabolic issues and have sensitive skin.

Kidney strain

This leads us to another potential cause. In naturopathy, it is often said that “the skin is the body’s auxiliary kidney,” and we frequently observe skin problems as a manifestation of suboptimal kidney function.

Pasture grass is significantly richer in certain nutrients, such as sugar, protein, and fat, which horses find difficult to process. During the hay production process, the drying procedure leads to a substantial loss of these nutrients. Elevated blood sugar levels put considerable strain on kidney function, as diabetics are well aware.

Grüne Weidewiesen im Sommer
© Adobe Stock/eyetronic

Excess protein needs to be broken down and excreted as urea in the urine. However, herbivorous horses have a limited capacity to excrete urea compared to carnivores. Moreover, horses struggle to metabolise fats efficiently, as they are naturally adapted to low-fat diets. Any substances that cannot be adequately processed by the liver and excreted through the kidneys often end up being expelled through the sebaceous glands of the skin.

Additionally, young and leafy grasses are often deficient in cellulose fiber but rich in soft pectin fibers. However, these fibers acidify the horse’s large intestine, potentially leading to dysbiosis (imbalanced fermentation). The byproducts of this faulty fermentation are absorbed by the horse’s body through the intestinal wall and must be eliminated through the liver and kidneys.

Endophytes and overgrazing

Furthermore, in overgrazed areas (where too many horses remain on too small a space for extended periods), the proportion of stress-tolerant performance grasses, characterised by high sugar and endophyte content, increases year after year.

The presence of endophyte toxins can be particularly challenging for horses as they pose an additional burden on the detoxification systems, especially when combined with high blood sugar levels and impaired kidney function. Consequently, horses are more prone to metabolic issues such as mallenders, sweet itch, lameness, and similar ailments when the pasture is “lush,” i.e., dominated by leafy performance grasses rather than diverse herbs and leaner grasses.

Accordingly, countermeasures should be implemented on multiple levels. If you have control over the pasture, adjust the grazing times to suit the horse population. It is better to have shorter grazing periods and longer recovery periods for the pastures instead of constant overgrazing.

Horses will not suffer if they have access to hay instead of prolonged grazing. In the case of limited space, it is preferable to create a small paddock trail with lean forage and ample opportunities for movement. In most cases, this is healthier for horses than a grazed-down monoculture of performance grasses that some may consider a pasture.

Muzzling the horse

Unfortunately, if you’re boarding your horse, you may not always have control over grazing times and pasture management (e.g., reseeding with lean grasses, protecting the areas, implementing rest periods, etc.). In such cases, it may be worth considering the use of a muzzle to limit the intake of performance grasses within a given time frame. Recent studies have shown that horses do not experience stress with a muzzle after an acclimatisation period, as long as they are designed to allow feeding (models with a small hole in the middle are usually problematic, especially in tall grass) and the muzzle is only used intermittently during grazing and not continuously for 24 hours a day.

The muzzle from the German brand “AS – Das Pferd im Blick” has proven to be effective, allowing you to adjust the feeding rate to match the horse’s ability and the condition of the pasture using different reduction plates. Additionally, it is advisable to reassess the contents of your feed bucket and consider reducing or eliminating cereals and other concentrated feeds that are rich in nutrients.

Pasture grass already provides horses with an abundance of nutrients, so there is no need to burden their metabolism with additional supplements. Often, by reducing nutrient intake during the grazing period, you can observe an improvement in the horse’s skin condition within a few days.

Herbal support

Furthermore, kidney function can be stimulated with appropriate herb mixes. When the kidneys produce more urine, the overall detoxification balance is relieved, enabling the horses to better cope with nutrient intake.

The “Detox Herbs” mixture from Okapi, for instance, has proven to be effective in this regard. Improved kidney function not only alleviates skin conditions but also aids in the sustainable healing of mud fever.

© Okapi GmbH

Supporting skin regeneration is also crucial, either by regularly offering a suitable mineral feed (such as Mineral Pur G) or by administering organic zinc and sulfur in a targeted manner (e.g., Zinc Chelate Plus and Sulphur Plus from Okapi), both of which are essential for skin formation.

Treating the mud fever crusts

If the horse only has mild crust formation in the pasterns, it is best to largely ignore them and focus on internal treatments. However, in cases of extensive crust formation, they should be removed, as bacteria and mites can colonize the crusts, making the healing process more challenging.

To remove the crusts, prepare a solution of water and curd soap (generously rub curd soap from the drugstore or pharmacy into warm water using a cheese slicer, stir to dissolve) and soak fleece bandages in this solution. Wrap the bandages around the affected legs and allow them to work for 10-15 minutes.

This will soften the crusts, making them easier to remove. Curd soap also has a mild disinfecting effect. Unwrap the bandages, wipe off any loose crusts, re-soak the bandages, and wrap them around again. Repeat the process until all the crusts are completely removed. Afterward, powder the skin with some baby powder (from the drugstore) and leave it alone. If the skin is superficially torn, such as in the crease of the fetlock, you can apply a small amount of regular nourishing cream (from the drugstore) or cod liver oil-zinc ointment (from the pharmacy) to keep the skin supple and promote healing. Hopefully, your horse will be free of mud fever with this treatment.

Experience has shown that allowing air to reach the affected areas leads to faster healing than wrapping them in bandages. When kidney function is stimulated and skin regeneration is supported simultaneously, “summer mud fever” often heals quickly on its own.