When you walk down the center aisle of your barn, does the ceiling drip condensation on your head? Does the smell of ammonia make your nostrils twitch and your eyes water--even when the stalls are freshly cleaned? Worst of all, was that a hollow, chronic cough you heard? From more than one of your barn's equine residents?

All of these are signs that the air quality in your barn leaves something to be desired. That's not at all uncommon, seeing as how barns tend to be designed more with human comfort than equine health in mind. Fearing bitterly cold winds, we build our stables to shut up tight in winter; we take care to seal up every drafty crack. In doing so, we block the very air flow so essential to our horse's respiratory health.

In some circumstances, horses might spend 24 hours a day in their stalls, especially when the winter weather has made paddocks sheets of ice, or sticky seas of mud. The air in a barn quickly can become stagnant and foul when horses are trapped inside-not surprising when you consider that practically everything in the environment of a barn contributes to poor air quality, from the dusts and molds in hay, grain, and bedding to the ammonia fumes emanating from equine urine and manure. 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. You want to sneeze just thinking about it.

Poor air quality is the culprit in a number of performance-limiting allergic responses in horses (usually lumped under the term COPD, for chronic obstructive pulmonary disease, and more commonly called "heaves" or "broken wind"). In addition, air quality has been implicated in certain types of non-allergic responses described as "small airway disease," which tend to affect younger horses and can have a major impact on athletic efforts on the racetrack or in the show ring.

Foals in particular are vulnerable to high levels of ammonia in the atmosphere, often succumbing to respiratory infections once their immature systems have been compromised by the fumes. There's also a demonstrated correlation between high antibody titers (indicating the horse's body has been fighting infectious agents) and horses which have been stabled when compared to horses which live outside 24 hours a day.

Inhaled dust particles and airborne pollutants can cause respiratory tract inflammation in their own right, and can overload the primary immune defense mechanisms in the throat and lungs, leaving your horse vulnerable to infection. When a horse breathes in dust and pollutants, he's also more likely to be breathing in high levels of infectious agents (including the bacteria and viruses, which cause respiratory diseases such as influenza and strangles). To make matters worse, inhaled dust can indirectly increase the duration and the severity of a respiratory infection your horse might already have contracted. Finally, dust can be an allergen, especially when it contains mold spores, pollens, and microscopic mites-any of which could trigger COPD.

Air movement within a barn is beneficial because it tends to sweep away the dust and mold particles-as well as the airborne viruses and bacteria-which are so much a part of the everyday environment of a horse operation. Unfortunately, our tendency to close any gaps or openings in a barn can interfere with normal air circulation, and trap those particles inside. In addition, it might trap moisture and noxious gases. Whenever you close a stable to keep it warm, your horses' lungs pay the price.

Good ventilation might be one of the most overlooked requirements of horse housing around the world. It's only recently that we've begun to understand the importance of good air quality for equine respiratory health, thanks in part to a series of studies by Guelph, Ontario's Equine Research Centre, and its director, Andrew F. Clarke, BVSc, PhD, MRCVS.

The ideal barn ventilation system, says Clarke, distributes fresh air uniformly throughout the building, helps minimize your horse's exposure to environmental irritants, and provides fresh air without drafts regardless of the time of year. For optimum respiratory health, your building should be equipped to allow at least six to eight "air changes" an hour (one air change being the time it takes for all of the interior air to flow out and be replaced with fresh). Air changes can be demonstrated quite effectively with a smoke puffer, a small device that fills the barn with harmless smoke, allowing you to watch how fast the smoke dissipates-and where it goes.

You don't need a smoke puffer to tell you if your barn's ventilation is inadequate. The signs will be around for you to observe-chronic coughs, horses diagnosed with heaves, water stains on the ceiling, or stale smells. It's probably safe to assume that most horse housing could stand to have its ventilation improved. Not to worry; that doesn't mean you have to re-design the roof, replace all the windows, or bulldoze your barn and start again. Improving the air quality in your barn is, in many cases, just a matter of making a few key changes.

Going With The Flow

Let's start by learning how air moves inside a building. As most of us know from years of watching meteorologists on TV, air movement is driven by differences in temperature. Cooler air enters a barn through openings close to the ground. Once inside, it mixes with warmer air (which has been heated by the bodies of the horses themselves). Then the warm air rises and tries to exit the barn through openings higher in the walls or ceilings. As it is displaced, more cool air is drawn in to replace it. This overall cycle of thermal buoyancy is sometimes called "the stack effect."

There are two other ways in which air moves in and out of a barn-aspiration, in which air is moved by the action of the wind blowing across the roof (drawing air out through any available opening), and perflatation, a fancy name that describes the way wind blows from side to side or end to end of a barn when openings allow it. The size of the building, the height and placement of vents or openings, and the distance between inlets (where cool air enters) and outlets (where warmer air escapes) all can have an impact on the effectiveness of a ventilation system. Other considerations include local geography and weather conditions-particularly topographical features like hillsides, hedges, trees, and the direction from which wind and driving rains usually come.

What if your barn does have poor ventilation? Will you have to smash holes in the walls to improve the air circulation, or install ceiling fans? In most cases, the answer is no. Some basic management changes, and a few interior details, can work wonders.

According to Clarke's research, many horses will show the benefits of increased air circulation simply when they are housed in stalls with open top doors, which allow them to hang their heads into the aisle. Stall partitions that stop short of the ceiling also assist air flow, as well as allowing horses the opportunity to socialize with their stallmates a bit. If you can persuade yourself to keep windows or doors open a crack even in winter weather, rather than shutting everything up tight, you'll be doing your horses' lungs a favor. Remember, horses are far more cold-tolerant than we are!

To make allowances for those few days when the doors must be shut tight, consider placing a permanent vent above the front door of your barn (such a vent generally can be installed by a contractor for relatively little cost). Vents at the back of each box stall, placed just under the roof, can assist air circulation by encouraging warm air to vacate and cooler air to begin to flow upward. (Windows serve the same function, with the added advantage of letting in some welcome sunlight.) If you're worried about drafts and weather coming in, install baffles on your vents or cover them with a plastic mesh such as Netlon.

A more ambitious undertaking is the installation of a capped chimney, covered ridge, or cupola on a peaked roof. Such alterations might be pricey, but they can provide a valuable outlet for warm, stale air (those cupolas on Kentucky barns aren't merely decorative!). If your barn ceiling has water damage from collecting condensation, you might need to consider taking a step like this.

"Natural ventilation is cheapest and best," says Clarke. "We've consulted on the building of very large barns equipped only with natural ventilation, and it works very well." It's mostly about making sure there are inlets and outlets to ensure good airflow; the rest is left to Mother Nature. If natural ventilation alone won't do the job (as it might not if your barn is sheltered by a hill, for example), you might need to look at some mechanical assistance. Ceiling fans are one solution; or you might wish to install a duct system complete with filters to help trap atmospheric particulates before they reach your horse's nostrils. Duct systems are most applicable for very large barns, where air might not circulate efficiently from one end to the other without help.

Finally, take a moment to think about insulation. Because an insulated barn maintains a slightly greater temperature difference between the inside and outside of the structure, air movement tends to be slightly intensified. As a result, you usually can get away with smaller (and fewer) vents to achieve the same ventilation effect. Insulation also reduces the risk of condensation buildup. It's not always easy to install insulation in an existing structure, but it's an option worthy of exploration.

Management Changes

What's the single most common source of dust and mold spores in an average stable? According to the Equine Research Centre's studies, it's hay. Susan Raymond, research associate with the Respiratory Health and Air Quality project at the ERC, explains that in one study, dry hay demonstrated dust levels dozens of times higher than hay cubes or pellets. A number of other forage types, including haylage (hay fermented and packaged in airtight plastic), generated significantly less dust, as did hay that had been soaked in water.

Bedding is another major source of inhalant particles in the equine environment. The worst offender, according to the ERC studies, is straw. Even the cleanest of wheat straw, it has been found, contains significantly more small, respirable fungal spores than most other beddings, such as shavings, peat moss, or shredded newspaper. Deep litter bedding systems, whether done with straw or shavings, are a major mold-producer. They allow molded bedding and fecal material to accumulate, and have the added disadvantage of allowing the buildup of noxious gases such as ammonia, not to mention infectious bacteria and the larvae of internal parasites.

"One of the worst things you can do," adds Clarke, "is to put your shavings pile, or the chute that brings the shavings down from the loft, right next to your horse's stall." Such a setup might mean your horse is inhaling irritant particles for hours every day.

Grain can be another source of airborne pollutants in the barn, especially when stored in bulk and under less-than-ideal conditions that allow the growth of fungi and molds. Needless to say, any grain that shows the slightest indication of being moldy should not be fed-quite apart from the internal upset, the number of spores a horse would inhale at the first bite represents a serious health threat to his respiratory tract.

Have you thought lately about the location of your manure pile? As manure and bedding break down in the pile, they can become a significant source of mold spores for any horses housed nearby. If your muck pile is too close to your barn, prevailing winds might be sweeping those microscopic irritants directly back into your horse's lungs. (Park that manure pile a little farther away and not only will you do your horses some good, but you'll get a little more aerobic exercise pushing the wheelbarrow those extra yards.) Likewise, try to remove your horses from the barn when you are mucking stalls. The dust and fumes you stir up could be damaging to his lungs. (It goes without saying that you always should strive to use a low-dust, quality bedding material and to muck your stalls on a daily basis.)

As you walk through your barn, look for other obvious sources of dust and pollutants. Is the shavings pile, or a large hay shed, right next to a window, for example? Do you see signs of mold in the hay or bedding? Might there be a tack room full of musty, fuzzy horse blankets that needed a good cleaning about six months ago? Do you have a loft full of 5-year-old hay that keeps sifting through the ceiling boards into your horses' stalls?

If the answer to any of these questions is yes, you need to take action to protect your horse's respiratory health. A few more simple tips follow:

  • Feed hay close to ground level, rather than in a hay rack where particles can sift into your horse's eyes and nostrils.
  • Wherever possible, wet all hay that is fed indoors-or feed a good quality, low-dust alternative forage such as hay cubes, beet pulp, or haylage.
  • Sprinkle the barn aisle with water when you sweep or rake.
  • Store your hay and bedding in a separate building, if possible.
  • Immediately discard any hay or bedding that shows signs of mold.
  • Make sure covered drains and pipes don't become clogged with feed or bedding; such an environment encourages mold growth.
  • Use a moisture-absorbing, odor-absorbing product such as slaked lime or Stable Boy on urine-soaked areas when you muck stalls.
  • Arrange to have your manure pile removed periodically so fumes don't build up.
  • Increase your horse's turnout time, allowing him to live outside (with shelter) as much as possible.

Applying some of these strategies to your everyday management routine can make a surprising impact on the air quality in your barn. You probably won't miss those condensation drips down the back of your neck, and your horse won't miss sucking up dust and mold particles every time he draws breath. These might be simple solutions, but they've got some profound implications.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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