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Stable Air

It was a mid-November day when her call came in. The owner of a stable that I had never been to wanted me to check out a horse with a persistent cough. I told Sandra to expect me at her barn the next morning. I got an early start that day. The half hour drive to the farm was a delight. It had rained lightly during the night and in the early morning hours a cold front had come through. The trees were sheathed in ice and the branches, back lit by the sun, looked as though they were cut from fine crystal.

As I pulled up to the barn, I noticed that the window on the front of the barn had a heavy frost on the inside. From years of visiting hundreds of barns I knew that this meant excess moisture inside.

I pulled open the big barn door and was immediately struck by the warm, sticky atmosphere in contrast to the crisp outside air. Sandra was sweeping the floor at the far end of the barn. She put the broom away and walked past the six horses’ heads looking out over their Dutch doors. I was introduced to each animal and given a brief history of each one. Sarah told me that she purchased the farm a few months ago and had recently moved the horses and her entire household up from Tennessee. She shared that she loved the beauty of winter but was having a hard time getting used to the cold. She was happy that I could come out that day, as another one of the horses had developed a cough just like the one she had called about.

As we chatted I glanced around. Not only was the window in front of the barn frosted over, but all of the others were as well. Sarah seemed open to new ideas, and I knew that our conversation was going to be mostly about the tired old air in her barn, and what it was causing.

We are coming into the season of equine respiratory problems. Every year, from October to April, there is a very predictable uptick in coughs and snotty noses. More serious diseases like the flu and strangles spread fast when horses are stabled. Cases of heaves often have their start in poorly ventilated barns.

The cause of all these issues is not the cold weather, but how we horse owners tend to react to it. We like to be warm and want our animals comfortable as well. So we tend to do what we do where we live. Shut the windows, seal all the cracks, and even insulate. We think we are being kind to our animals. The result is stable air like Sarah’s, stale and filled with moisture.

Each average adult horse gives off a full gallon of water in his breath every day. Add to that the moisture from manure, urine, and sweat, and in a tight barn the air becomes super saturated with moisture. When barns are buttoned up, the heat given off by horses raises the air temperature. Warm air holds much more moisture than cold air. Dairymen have known this for years. They fit far more cows per any space than we do horses. The temperature in a dairy barn even on a 0 degree Fahrenheit day would be well over 80 degrees if it weren’t for big fans pulling out the stale air 24 hours a day. Viruses and bacteria thrive in the heat and humidity. It is almost impossible to clear up a respiratory problem in a barn where the air is rebreathed.

Sealing a stable to keep out the cold is well intended but is a big mistake. When you seal out the cold, you seal in the moisture. The evidence is seen on the frosted windows and walls where the moisture condenses on a cold day. Horses can withstand the coldest New England weather as long as they have plenty to eat, are kept on clean dry bedding and there is good ventilation.

Our ancestors knew of the problem and built in a natural draft system to combat it. They designed their barns so that there was an air space under the eaves. The cold air entering there dropped down the walls, and mixed with the warm moist air. This tempered air rose and exited out the cupola on top of the barn. In almost all horse barns this old natural draft system should work without depending on fans. Today in most cases ridge vents at the top of the roof take the place of the cupola. The beauty of a natural draft system is that it is self-regulating. The greater the difference in temperature between inside and outside, the faster the warm air will leave. The warm air with its capacity to hold water is vented out. In a natural air flow system air inlets and outlets are equally important.

I was surprised by the amount of information on line about the importance of barn ventilation. There are over 1000 articles listed! Of the ones I skimmed, the best is a 16 page article entitled “Horse Stable Ventilation” from Penn state. It is quoted by many of the others, and explains in detail with lots of excellent drawings how to build or retrofit a barn for ventilation and optimum health.

I examined Sandra’s two coughing horses. Within two weeks of minimal medication they were fine because with very little expense the air in Sandra’s barn was being changed four or five times every hour and the flow distributed evenly throughout the stable. Sandra had learned the importance of fresh air and has not had a coughing horse since.


David A. Jefferson, DVM

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