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Free Faecal Water Syndrome – As the winter continues, it is seen more frequently in many stables. This is not just a cosmetic problem. It’s not just an unpleasant sight to see the brown slurry running down the horse’s legs – the faecal water urgently needs to be washed off, as it is aggressive and attacks the skin, which can lead to inflammation (dermatoses).

Especially in frosty weather, however, washing the tail and hind legs is a rather non-fun activity for everyone involved. In addition, FFWS is also an indication of massive malfermentation in the horse’s large intestine (dysbiosis), which is often accompanied by stress. If you don’t take action here, there is a risk of serious health problems in the long term.

What is FFWS (Free Faecal Water Syndrome)?

While horses with diarrhoea produce piles similar to cow dung, those with FFWS exhibit a shape more akin to traditional horse droppings. This indicates that the fluid has been extracted from the faeces during the intestinal passage, yet ‘free water’ is generated again in the large intestine. Brown fluid is secreted either during or after defecation, or even independently of it. In mild cases, the time that faeces remain in the rectum is often sufficient to absorb the small amount of faecal water before excretion.

Visually, the horses do not have FFWS. It becomes noticeable only when horses are under stress and have more frequent droppings; in such cases, there is no longer sufficient time, and the FFWS becomes suddenly visible. It was already there before, but hidden in the horse droppings. These horses often produce very liquid droppings; stepping on one leaves a large, wet stain. Naturally, horse manure tends to be quite dry, and it shouldn’t be possible to squeeze it out like a sponge.

It’s not uncommon for owners to mention that their horses only experience Free Faecal Water Syndrome in the winter, so it’s perceived as less concerning. However, it’s crucial to bear in mind that winter doesn’t last just three days; rather, the horse may have FFWS for about half a year.

While digestive problems may somewhat stabilize during the grazing season in summer, FFWS remains a year-round issue. Not only does it frequently worsen from one winter to the next, but the horses themselves also experience stress due to this condition.

The assertion that all horses in the stable have FFWS and that this is considered normal is quite alarming. It’s worth noting that until a few decades ago, the condition ‘Free Faecal Water Syndrome’ did not exist at all, and in many languages, there is still no term for it today. No, FFWS is not normal. It is a symptom of a massive health problem that we ourselves cause in our horses in our countries – a classic disease of civilisation in horses.

What could be causing all this?

FFWS is usually the visible symptom of an inflamed intestinal mucosa. It is not merely a visual problem; rather, it has several negative effects on the horse’s health. Inflammations are typically caused by incorrect fermentation processes in the large intestine.

The reasons for this can be attributed to either the housing or feeding conditions. study has demonstrated that even stress alone is sufficient to trigger FFWS. Stress leads to reduced blood flow to the intestinal mucosa. This slows down peristalsis and can result in incorrect fermentation. But feeding also plays a major role. Incompatible feeds such as haylage, silage, or corn silage play a significant role here, as do ‘structured muesli’ or many pro- or prebiotics advertised as beneficial.

Bales of haylage
Incompatible forage such as haylage, silage or corn silage play a role in Free Faecal Water Syndrome (FFWS). © Adobe Stock / Westwind

Ensiled forage introduces a significant amount of lactic acid bacteria into the large intestine, which is not present to the same extent in the intestine of a healthy horse. They produce lactic acid, which acidifies the intestine. As a consequence, natural intestinal symbionts die off, leading to the entire fermentation process spiraling out of control.

Finely shredded roughage, found in textured mueslis, grain-free mueslis, or many herbal mueslis, also hinders peristalsis since these short fiber shreds are often not thoroughly chewed.

Studies have indicated that these fiber lengths can persist in the large intestine for up to a week. Nevertheless, any disruption to the digestion speed can result in incorrect fermentation (dysbiosis) and, consequently, health problems.

These incorrect fermentation processes often generate large quantities of acids, which can harm the intestinal mucosa. Unlike the stomach wall, the intestinal mucosa is not shielded against acidic pH values. This results in inflammation of the intestinal mucosa, further disrupting the normal digestive process.

If the inflammation persists for an extended period, the cell structures of the intestinal mucosa loosen, leading to the development of ‘holes’ that the already overburdened immune system cannot adequately repair. These holes can allow lymphatic fluid to seep into the intestine, manifesting visually as FFWS.

Acidification of the colon becomes a vicious circle

Even if the original cause, such as a winter of haylage feeding three years ago, occurred a long time ago, it can still disrupt digestion today. This occurs because once the pH value in the intestine rises, acid-forming microorganisms can proliferate, leading to a continuous decline of the natural intestinal flora, which relies on a neutral pH value. Even with perfect feeding and keeping conditions, the situation often doesn’t improve significantly at first.

Once the intestines have been heavily colonized with harmful microorganisms, horses often find it challenging to break out of the vicious circle of intestinal disorders and FFWS on their own.

Stress doesn’t just make people ill

Moreover, the role of stress as a cause of Free Faecal Water Syndrome should not be underestimated. Many riders believe that their horses can’t experience stress because they are not required to perform a strenuous job to earn a living.

wide open horse eye
The role of stress as a cause of Free Faecal Water Syndrome should not be underestimated. © Adobe Stock / hhurma13

It is often overlooked that our conditions of keeping and feeding present numerous sources of stress. These factors include excessively large groups in open yards or those with poorly socialized horses. High or low status in the group can also be linked to stress.

In stall conditions, stress can arise due to a lack of exercise and unfriendly neighbors. Extended breaks from roughage or ‘controlled roughage supply’ through portion feeding or automatic hay dispensers, a limited number of feeding spots, inadequate or sparse bedding leading to insufficient sleeping opportunities, and, notably, the absence of the chance to engage in natural activities like running and bucking in winter can all contribute to the development of stress-related FFWS.

Finding the causes of stress is not always easy. At times, even after optimizing every aspect to the best of your ability, there’s still no improvement. Perhaps a horse moves out of the group, or you find yourself changing stables, and suddenly the therapy becomes much easier. Frequently, we may not readily identify what is causing stress in the horse, but it’s always worthwhile to take a closer look.

There is no “miracle cure” for FFWS

Even if a horse only exhibits FFWS in specific situations, such as during trailer loading or when the farrier comes, or if it only occurs in winter, it indicates the presence of digestive problems in the large intestine. Over the long term, horses affected by Free Faecal Water Syndrome often develop cryptopyrroluria (KPU) and its associated symptoms. Upon reaching this stage, the therapy often becomes even more complex.

Diagnosing incorrect fermentation in the large intestine can be done through the assessment of the Indican value. As a horse owner, you can often order a urine tube directly from the laboratory to have the Indican value determined. If the Indican value is 0, it indicates that the fermentation process in the large intestine is running normally. A value of 1 suggests that feeding should be optimized, and if necessary, the intestines should be supported with naturopathic remedies to quickly stabilize the fermentation processes.

If the Indican value is between 2 and 4, significant changes to the feed and possibly the keeping management are necessary, along with measures to cleanse the intestines. Extended treatment times should be anticipated in such cases, as additional initial symptoms alongside FFWS often suggest a derailment of metabolic processes.

However, a sensible treatment of FFWS always requires consideration of many aspects. A species-appropriate diet plays a major role here, necessitating the elimination of all feeds that do not strictly adhere to the horse’s natural diet. However, housing conditions with all potential stress factors should also be thoroughly examined, along with the level of exercise and other potential underlying conditions, such as cardiovascular problems or worm infestation. Therapy can only be successful if all aspects are addressed correctly.


Free Faecal Water Syndrome (FFWS) is more than just a ” aesthetic blemish”, it is an urgent warning signal. The causes of stress, feeding errors, and the potential consequences of these on metabolic health should not be underestimated.

More on this topic: Top 5 Reasons for Free Faecal Water Syndrome (FFWS)