Neutra - Sources of odours in stable environments


The pungent odour that often emanates from stables is not very inviting. The smell does not only drive away customers, it can even lead to legal disputes with neighbours. Fortunately, odours can be controlled through good planning and the proper routines.

The first step is to find out what is causing the odour. The two main sources of odours in stables are manure and urine. Horses spend around 17 hours a day feeding. A single 1000-kilo horse produces on average 31 kilos of droppings and 9 litres of urine a day. Add to this all the dirty bedding and the total is over fifty kilos of waste per stall. This waste is one of the main causes of bad odours.

When manure decomposes, odours are created if there is not enough oxygen mixed in with the manure. When composted correctly, manure should not smell. Good drainage, absorbent bedding and daily cleaning all help minimise the causes of odours by prolonging the process by which they are produced.

The pungent smell of urine is the result of ammonia. If horses are fed more protein than their bodies can process for the production of bones and muscles, nitrogen in the form of ammonia is converted into urea. The excess urea is then released through urine.

Consequently, horses that are fed high levels of protein most likely have wetter and smellier stalls. In order to manage the odours caused by manure and urine, the location of the stables along with hygiene, ventilation and waste management all play key roles.


Owners should pay close attention to how their stables affect the surrounding environment and to the opinions of neighbours. Waste management in the equine sector is regulated by law, so check to see if there are any local regulations regarding the treatment of manure and comply with these regulations in order to avoid problems.

The storage facilities for manure should be situated as far away as possible from neighbours to help prevent odours from spreading over their properties. Moisture accelerates the decomposition of manure, releasing odour-causing gases during the process. To control these gas emissions within the stable and in the surrounding environment, adequate drainage is essential.


Cleaning manure, urine and dirty bedding on a daily basis goes a long way towards controlling odours. Stable workers should be instructed to remove wet bedding from beneath water troughs and to collect excess hay that the horse has not eaten, as these places are prone to bacteria growth.

Minerals, such as lime or zeolite, can be spread on wet areas after removing the urine in order to absorb moisture and gases, thus neutralising any remaining ammonia. Lime has been used traditionally in stables to help control odours and keep stalls dry, but the downside is that lime can be dusty and create slippery surfaces. When released into the air, the tiny particles from the lime can irritate the respiratory tracts and eyes of both humans and horses. Pine oil is effective for controlling odours but not for drying, and it can also irritate respiratory tracts.

Non-clumping cat litter has also been tried in stables. Cat litter helps keep stables dry, but it is not very effective in controlling odours. Organic cat litter often contains corn and wheat byproducts that can make horses eat it. Horses can also be sensitive to fragranced cat litter.

When the stall is dry, spreading pleasant-smelling sawdust is a good way of covering any remaining odours. Other good bedding materials are wood pellets, peat and straw pellets. These pellets are relatively new on the market and are recommended for their absorption qualities and ability to control odours.

The most important aspect of cleaning is to have strict routines. Cleaning stables once a day is not necessarily sufficient. Stalls should be cleaned at least twice a day. This will prevent odours from building up and reduce the amount of work on the following day. In this way, horses will feel better and stable workers will have an easier job. Wet bedding and urine should always be removed immediately to control ammonia levels. Major cleaning should be carried out once a week. Stalls should be emptied completely while the horses can be outside until the stalls have been allowed to dry thoroughly. Letting the horses out during cleaning will protect them from the dust and ammonia. Stable workers should wear respiratory and eye protection to protect against ammonia gases that may be released.

Removing manure from outside areas where horses gather, such as around hay, steps and doorways, will help prevent odours from being spread by the wind. Manure should be spread out into thin layers using the appropriate spreading equipment to allow it to decompose into the soil faster. To minimise odours, manure should be spread out in the early morning when there is typically less wind and before the manure has a chance to heat up in the sun.


Horses generate heat and humidity. When these are combined with the gases produced by decomposing waste materials, odour levels will increase. Stables should have sufficient ventilation to remove humidity and gases, as well as to regulate the indoor temperature. Doors and windows offer a natural form of ventilation in stables where the stalls are located against or near the outer walls. In stables where the stalls are located along a central corridor, ventilation can be facilitated by having doors at either end of the corridor.

Windows and air vents also facilitate natural ventilation. Fans are usually needed to improve the natural ventilation, especially in warm weather. When selecting a fan system, factors to take into consideration include the structure of the building, the number of horses and the outdoor temperature.

According to the latest EU regulations, new stables should have higher ceilings to allow a higher volume of air and reduce the health risks related to poor ventilation. A build up of moisture inside stables can enable mould to form. The combination of warmth and humidity in structures increases the breeding ground for moulds and funguses. The recommended maximum humidity level in stables is between 60 and 65 percent. Each horse adds around 500 grams of moisture an hour to the air. Good ventilation will help ensure that the humidity levels are kept under control. Excessive humidity poses a risk to the health of horses and over time will also cause structural damage to stables.

Impact of stables on the environment

The main environmental impacts from stables are run-offs from manure piles and outdoor stalls. These run-offs can contain large amounts of phosphorous that can pollute waterways. Nutrients from manure can be absorbed by bedding inside the stables, but outdoors the manure can easily spread with water. Collecting excrement is important for reducing nutrient discharges. The nitrogen and phosphorous content of manure can be reduced by changing the mineral and protein contents of the feed according to the horse’s needs. Composting manure improves its fertilising value, but it also increases leaching. This can be reduced by protecting the manure from rain.

Following changes in EU regulations, the combustion of manure from farm animals is now permitted without having to obtain a waste incineration permit. Previously, manure combustion was not permitted in any EU country except at waste incineration plants. The changes were approved on 17 January 2017 following an initiative by Finland.

Stables are both a habitat for horses and a place where people spend a lot of time. Stables that smell are not very inviting environments. The bad odour is not the only downside, however. Bad odours are also harmful to our health. Accordingly, close attention should be paid to the causes of bad odours for the sake of the health of both humans and horses, as well as for the overall quality and comfort of the stables. Fortunately, effective additives are available that minimise odours by absorbing moisture and preventing ammonia emissions. The use of these additives has been studied at numerous Finnish stables with excellent results. Discover for yourself the benefits of the Finnish product Neutra.

Want to learn more about choosing the optimal bedding for your stalls? Download the article >>