When winter hits, horse people have a tendency to shut those barn doors tight. But we may be doing our horses' respiratory systems a grave disservice. In winter, your horse may spend 24 hours a day in his stall. But the air in a barn with inadequate ventilation can very quickly become stagnant.
Practically everything in a barn environment contributes to poor air quality, from the dusts and molds lurking in hay, grain and bedding, to the ammonia fumes emanating from urine. Fungal material, bacteria and viruses, particles of fecal matter, methane, hydrogen sulfide, even microscopic bits of plant material and insect parts all are measurable pollutants in stables.
Poor Air Brings on Allergies
The dust that circulates in a closed barn can worsen allergies in horses of all ages, and this gets to be a big problem in older horses. The extreme example is the older horse with 'heaves', but earlier symptoms of cough and exercise intolerance can result from poor air quality in younger horses.
"Whenever you close up a building to keep it warm, the lungs have a price to pay," says Andrew Clarke, Director of the Equine Research Centre at the University of Guelph, Ontario, in Canada. There is also a demonstrated correlation between the incidence of infectious respiratory diseases, such as influenza and strangles, and stabling rather than keeping horses outside
We're beginning to understand how improving ventilation in barns and stables can improve or protect equine respiratory health. The ideal barn ventilation system distributes fresh air uniformly throughout the building, without causing drafts, at all times of the year. This serves to helps minimize your horse's exposure to environmental irritants, explains Clarke.
Gentle consistent air movement within a barn is important because it tends to sweep away the dust and mold particles, as well as airborne viruses and bacteria. Our tendency to close up any openings in a barn can interfere with normal ideal pattern air flow and trap those particles inside, along with moisture and noxious gases. Of course, not any airflow will do. If circulated air is chaotically causing turbulence, but is not replaced by outside air at a sufficient rate, dust will remain suspended, putting horses at further risk of greater exposure. Hence, a ventilation system needs to work right.
Sources of Dust and Mold
Sensitivities to dusts, molds and other inhalants vary a great deal from horse to horse, so it can be difficult to predict which horses will develop respiratory disease. But we can at least identify some of the common culprits.
Hay is the single most important source of dust and mold spores in the stable. Susan Raymond, Research Associate with the Respiratory Health and Air Quality project at the ERC, explains that in one study her team compared the relative dust levels of five different types of forages: dry hay, water-soaked hay, haylage, hay cubes and a complete feed pellet. Dry hay, even that which looked to be of very high quality, consistently demonstrated dust levels dozens of times higher than hay cubes or pellets.
Bedding is another major source of inhalant particles in the barn. The worst offender, according to the ERC studies, is straw. Even the cleanest wheat straw contains significantly more small, respirable fungal spores than other types of beddings.
Wood shavings can be problematic too. "One of the worst things you can do," says Clarke, "is to put your shavings pile right next to your horse's stall." Such a setup may mean your horse is regularly inhaling irritant particles.
One type of bedding that is unusually low in dust is shredded paper. The amount of airborne particles generated during mucking-out with this bedding, according to Raymond, was much lower than with straw bedding. Paper is a bit tricky to handle, however, as it requires very dry storage and becomes quite heavy when soaked.
Though it may sound obvious, it's important to muck out your barn every day, otherwise ammonia fumes from urine-soaked bedding can accumulate in the environment and further irritate your horse's lungs.
Even grain can be a source of airborne pollutants in the barn. The poorer the quality of the grain you feed, the higher the dust levels. Poor quality is suggested when you see a dust residue in feed buckets, for example. Pellets and extruded feeds usually have lower levels of fine dust residues than whole grains. Not only can grain dust be inhaled by the horse, but molds can grow on the grain which cause airway inflammation. Needless to say, any grain that shows the slightest indication of being moldy should not be fed. Mold can accumulate on the walls of wooden or even plastic food storage bins, so they need to be thoroughly disinfected several times per year.
Improving Air Quality
Hay is the principal source of mold in your horse's breathing space. Therefore, your effort has to be directed at buying the best hay. You must avoid the purchase of hay with the least bit of indication that it carries mold. Mold grows on hay if was bailed under conditions of excess moisture. When hay is bailed when even slightly damp, it heats up. It's that warm environment inside the bail that molds really like. The bails eventually dry out, killing the molds within, but not before billions of tiny spores are released as a legacy to the molds. The mold spores, which are invisible and odorless, are inhaled by your horse when the bail is cracked open.
When possible, store your hay and bedding in a separate building rather than in a barn loft. Chaff and dust from hay stored above can sift down and trigger respiratory problems. Moreover, old hay and bedding can form a layer on the loft floor, providing an ideal environment for mold growth, as well as a hiding place for rodents, sparrows and other uninvited residents.
Barns should have inlets or vents, where cool air enters, placed under the eaves. In a mild climate, they may take the form of open windows; in a colder one, screened vents with adjustable openings that prevent drafts may be a better option.
The inlets of a barn should be complimented by sufficient outlets, where warmer air escapes. Optimally, these would be located closer to the roof. The net effect is to encourage air to enter the bar, dip down, and rise when heated to exit higher up.
A natural ventilation system like this can be used in cooler climates that are relatively open. In warmer climates a ceiling fan or fans at the outlets may be necessary to move enough air. In warmer climates and in tighter barns, you may have to install a duct system, complete with particle filters that can trap atmospheric particulates before they reach your horse.
Move that manure pile further from the barn, and resist the temptation to close every crack and cranny of the barn up tight when the weather gets chilly. Instead, blanket your horses and allow a little breeze to come through.
Ultraviolet light from the sun is a potent killer of a wide range of airborne viruses, bacteria and even parasite eggs and larvae. Windows and skylights installed throughout the barn can contribute to a healthy environment. If you install skylights, use plastic or U/V light translucent glass rather than normal glass; both allow more of the useful U/V rays to penetrate.