Most of us take pride in having a clean barn and pat ourselves on the back that there's no offensive odor-at least to fellow horsemen. However, you may not realize that even though you can't actually "smell" anything, there's a constant release of gases from manure and urine that can assault your horse's lungs.
Most studies implicate fine particulate matter and endotoxins in the air as the primary factors, and they are indeed important. However, ammonia concentrations at the floor level are much higher than in the barn air in general, and the horse will get a concentrated dose when down sleeping or resting. That's where stall fresheners and deodorizers truly have a place in wise barn management. It's simply a matter of good health.
How Do They Work?
Step one for a fresh, healthy barn is plain old stall cleaning. That means keeping stalls well picked out and the removal of soaked bedding and pooled urine. Good ventilation is also extremely important. However, that still won't completely eliminate ammonia. Ammonia is produced by bacterial breakdown of urea in urine and unabsorbed protein in manure. Stall-freshener products are designed to give you extra ammonia control.
Simply absorbing urine helps reduce ammonia by making the urea less available to bacteria. For example, stalls with paper-based beddings have less ammonia than stalls with straw. Diatomaceous earth is also highly absorbent.
Stall fresheners go one step further when they're mineral-based. Zeolites, montmorillonite and Bentonite (which is primarily montmorillonite) clays actually chemically bind ammonia molecules. This binding process is called adsorption.
Montmorillonite can bind both urea and ammonia, but binds them irreversibly. Zeolite binds only ammonia (urea isn't the odor problem), but can release it again so it acts as a slow nitrogen fertilizer for soil. Of the two, our testers thought the zeolite gave better ammonia odor control, but montmorillonite absorbed more moisture.
Yucca saponins have been proven to reduce ammonia production, although the exact mechanism is unclear. Natural-source adsorbents and adsorbents from plants may also be used.
Since the production of ammonia depends on bacteria, a variety of approaches gear ingredients toward the bacteria. Stall Dry Plus contains a chemical antimicrobial.
Two spray-on products take the opposite approach by supplying live bacteria that will breakdown ammonia and other organic waste products. Surfactants also disrupt bacteria. Enzymes may be added to help breakdown of ammonia and other malodorous wastes in manure.
Mucking stalls releases ammonia and stirs up dust, mites and mold spores. Finely ground stall fresheners are also potentially irritating to you and your horse. Try to remove your horse from his stall during stall cleaning, if possible, especially if you're using a powdered deodorizer, and keep the barn well-ventilated.