Effective Housing Ventilation

Good quality ventilation – why?

Effective ventilation in all equine housing facilities is essential. The objective is to provide fresh air to the horse, and is achieved by providing sufficient openings in the building so that fresh air can enter and stale air can exit. Stale air comprises of moisture, heat, pathogens, dust and ammonia. Stuffy stables and their poor air quality are the result of limited air exchange and /or obstructions to the entry of fresh air to the building or exit (at roof height) of stale air leaving the building.

Images above show Ridge outlet venilation

Moisture, odour, and ammonia are generated mainly in the stables, where fresh air is needed for horse respiration and to dilute air contaminants. Since most dust and ammonia are generated near the bedding and manure, check air quality near the floor as well as at horse head height. Floor level air quality is particularly important for foals or when horses eat at ground level and spend time lying down. It is not uncommon for a barn aisle to be well ventilated while the stables suffer from stuffy conditions for example.

Irrespective of what your enterprise is, ventilation has a key role in maintaining horse health. Horse’s airways are vital to both their performance and wellbeing. To be able to perform at their very best, horses need to be in an environment that has clean fresh air and is free from disease pathogens.

There are three categories of airborne irritants that adversely affect horses: contact irritants, airborne allergens and infectious agents all of which can prevail in poorly ventilated environments.

Examples of contact irritants are ammonia or dust particles that physically ‘hit’ the airway, create clogs and need to be cleared with a snort or cough. They can invoke a mild inflammatory response without an immune response and are the trigger for overproduction of mucous and constriction of the lower airways. However if irritation persists the respiratory tract becomes more vulnerable.
Airborne allergens include moulds, and pollens from hay / forage dust which invoke a mild to severe immune response. The outcome may be periods of laboured breathing, a chronic cough and severe nasal discharge.
Infectious agents are bacteria, fungi and viruses which provoke a severe immune response and erode the airway defence mechanisms. If infection overwhelms the immune system the horse may become lethargic, reduced/no appetite, feverish, have a nasal discharge and/or cough.

Asthma/ Inflammatory airway disease is a chronic disease that develops as a result of constant irritation and immune responses to contact irritants and airborne allergens. Irritants continuously trigger the immune response and a horse may have what resembles an asthma attack. Asthma is common, debilitating and an easy way to help prevent this and other respiratory diseases such as exercise induced pulmonary haemorrhage (bleeding from the nostrils at exercise), recurrent airway obstruction (airway narrowing, mucous production and airway spasm); is to remove the high concentrations of irritants. Ventilation has a key role in this regard. Equally important is vigilance on other biosecurity measures such as disinfection, testing of feed, fodder and bedding for quality while also making sure that fodder and bedding storage is of high standard to protect the quality.

Good quality ventilation – what is it?

The cornerstones of good ventilation are adequate airflow, without drafts, equally distributed throughout the facility comprising six to eight changes of air every hour. This means a minimum of an air change every ten minutes per stable. Anything less than this leads to dampness and mould which in turn results in respiratory disease and health issues.

Good quality ventilation – how?

Good quality ventilation is achieved by designing openings in the building which allow fresh air to enter and stale air to exit. There has to be an entry and an exit, and one without the other does not work.

Effective ventilation consists of natural airflow above horse head height which is permanent open ventilation, and an exit vent at the highest point in the roof space. Air inlets above the horse’s head allow intake of air no matter what direction the wind is coming from. Inlet ventilation can be achieved using continuous eave openings; Yorkshire boards; vented sheeting; openings with bird mesh covering. Any ventilation below head height (doors/ windows) should be controllable based on weather conditions to avoid drafts.

Images above show inlet vented sheeting from both external and internal views

Poor ventilation examples include absence of roof vents; no inlets other than doors / windows; inability to close doors / window; stables sharing internal side walls with for example a manure pit (ammonia)/ riding arena (dust)/ other stables or the flow of air blocked by perhaps a large quantity of trees directly alongside stabling. The quality of the air entering the facility must be freeflowing clean air in other words. Interior ceilings are also not advised. When the housing is open to the ridge more air exchange and distribution can occur. It is also important to note that hay or straw should not be stored overhead of stables. Not only is this a fire hazard but also a haven for dust and allergens.

There are two processes at play where ventilation is concerned and they are

Air Exchange (Fresh air replaces stale air)

Hot air rises and cool air falls. The basic principle when trying to move and remove air is to pull fresh cool air in from below and pull hot air out from above. Denser colder air lifts warmer air up and out of the building. When this happens, as the hot air leaves it removes moisture, dust, heat and pathogens, as well as ammonia with it and leaves a fresher cleaner stable environment as a result.

Air Distribution (Fresh air is available evenly throughout the stable)

The diagrams above illustrate positioning of inlets and outlets with air entering above horse head height and leaving at maximum roof height allowing the process of ventilation to occur.

Conclusion

Well ventilated stables are vital for horse health and coupled with good management practices is absolutely critical. Good ventilation allows plenty of fresh air into the stable at a height that doesn’t cause a draft. Housing should be built to optimise the health and well-being of the horses, not the creature comforts of people. Horses have a wider range of climate tolerance, especially in cold weather than humans. Tightly enclosed barns might be warmer in the winter for the horse owner, but may have poor ventilation resulting in increased respiratory and pathogen driven illnesses in horses.