Managing Ammonia in Horse Barns

By Dr. Thomas Lenz in The American Quarter Horse Journal

Walk into many horse barns this time of year, especially if they are closed or have poor ventilation, and the acrid stench of ammonia burns your nose and causes your eyes to water.

Moderate to high ammonia levels in barns are not only irritating to mucus membranes but increase our horse’s susceptibility to serious respiratory infections.

Horses excrete urea in their feces and urine to eliminate excess nitrogen from their bodies. While urea is odorless and nontoxic, it is rapidly converted by bacteria to ammonia in the soil and bedding.

Ammonia is not only foul smelling, it also inhibits the movement of cilia, the tiny finger-like projections that line a horse’s respiratory tract and that are responsible for sweeping fluids and foreign particles up and away from the lungs. When the horse’s cilia are less efficient, the horse is much more susceptible to respiratory infections, including pneumonia.

Keep your horse healthy by staying up to date on diseases and illnesses. AQHA’s Common Horse Health Issues report will help you develop a knowledge base of common maladies, and precautions you should take to protect your horse.

Chronic ammonia exposure can lead to inflammation and constriction of the horse’s airways and mucus accumulation, ultimately resulting in the development of recurrent airway disease (heaves).

While the exact levels of ammonia that are detrimental to horses are currently unknown, veterinary researchers have shown that ammonia levels in an average horse stall can exceed 200 parts per million. For people, the U.S. Occupational Safety and Health Administration has set a 15-minute expo¬sure limit for gaseous ammonia levels of only 35 ppm, so you have to wonder if the same is not true for horses.

Because ammonia concentrations are greatest near barn and stall floors, horses that are fed on the floor or spend long periods of time lying down are exposed to the highest level of ammonia.

The good news is that ammonia concentrations in stalls can be dramatically reduced by simple environmental management. On average, a horse produces 0.5 ounces of feces and 0.3 fluid ounces of urine per pound of body weight each day. So a 1,000-pound horse will produce 31 pounds of feces and 2.4 gallons of urine each day.

Knowledge of horse diseases and illnesses is not just for vets. AQHA’s Common Horse Health Issues report has the information you need to be a responsible and educated horse owner.

So when building a new barn or refurbishing older stall floors, it is important to first put down a subfloor of 8-12 inches of 4- to 5-inch gravel, covered by a few inches of small gravel and then covered by a mixture of clay and stone dust (2/3 clay and 1/3 stone dust) or a mixture of clay and sand (2/3 clay and 1/3 sand) that will allow urine and water to drain away from the floor. Sand alone is porous but increases the potential for sand colic when the horse eats off the ground. The subfloor can then be covered by rubber mats or several inches of good wood shavings or straw. Other steps to reduce ammonia levels are:

• Consult your veterinarian or equine nutritionist for the best ration for your horse’s needs. Many horses are fed rations higher in protein and nitrogen than necessary, which results in excess urine production.

• Let your horses outdoors to exercise as much as possible, not only to cut down on stall time but to improve their overall health.

• Ensure that the barn is well ventilated.

• Remove manure and wet bedding daily; completely strip the stall at least weekly. If possible, remove your horse from the stall while you clean, as ammonia will be stirred up by the cleaning process.

• Choose absorbent bedding and consider mixing a quality neutralizing product with the bedding. Choose a product that actually neutralizes the ammonia and doesn’t merely cover up the odor. Lime-based products have traditionally been used in horse barns. However, they do a poor job of neutralizing ammonia and can cause severe irritation and burning of the horse’s eyes and skin. There are a number of commercial products that are nontoxic and trap or eliminate ammonia.