Managing your barn is a time-consuming labor of love. Your horses flourish in a clean, fresh-smelling barn environment, but a dirty barn can breed disease and insect infestations. Hydrated lime can be used to help keep the stalls clean, but it brings its own set of safety hazards into the barn.
Flies can pester your poor horses incessantly, especially when they find damp areas in your barn that are ideal for laying eggs. Hydrated lime absorbs some moisture, which can reduce the chances of flies laying eggs in your barn. Lime also can change the pH of soil, but that doesn't affect fly growth; maggots can tolerate pH changes if they hatch near lime. If you're looking to control flies in your barn, hydrated lime is not your best option.
The main purpose for hydrated lime in your barn is to reduce the smell of ammonia. This smell develops from horse urine, especially when the stalls don't drain properly and the urine pools in one area of the stall floor. Spreading lime on the floor after you muck out the stall can help absorb moisture and remove some of the ammonia smell, especially when covered by absorbent bedding material.
The ammonia smell can be dangerous to horses, causing respiratory problems over time. This is more of a problem with foals because of their developing immune systems, and the fact they tend to lie on the floor, closer to the smell, more often than adult horses. Lime can help with the smell, but it's not a perfect solution. It can irritate a horse's skin if he touches it. If the hydrated lime somehow gets into your horse's eyes, it can cause permanent damage. Breathing in lime dust also can lead to respiratory distress.
There are several alternatives to using lime in your horse stalls. To help combat flies, downward-pointing fans above the barn doors can be effective, as can the low-tech sticky fly paper. Insecticides can help control infestations, but you must treat any moisture issues to prevent further fly breeding. For ammonia smells and stall moisture, try products made with diatomaceous earth, clay or zeolites, which absorb moisture effectively without causing any respiratory problems. They also help absorb odors, removing dangerous ammonia smells.