Is agricultural lime safe for horse stalls?

Q:There has been great debate at the barn I board at regarding lime.

The barn manager likes to sprinkle it on the wet spots of stalls to neutralize the smell. She then covers the area with new bedding. Some owners, however, think lime is dangerous to their horse’s lungs. Others say it dries out their hooves. Is there any evidence that agricultural lime is harmful to horses? Are some types worse than others?

A:I’ve done a bit of research and there isn’t any actual scientific evidence that I can locate that indicates agricultural lime (also called barn lime or gardening lime) causes problems for horses. Agricultural lime’s primary ingredient is calcium carbonate, which is nontoxic and used in human antacid products. However, so-called “caustic limes”—including quicklime and hydrated lime—have been processed in a way that can cause them to “burn” skin and vegetation. Those are best avoided for all home, garden and barn usage.

That said, since agricultural lime is essentially ground stone, some humans and horses may be sensitive to inhaling it, as they would any fine powder. For that reason, it’s probably best to apply it to stalls when the horses are not in them and wear a mask as you do. You can purchase agricultural lime in pelleted form, which can further reduce the risk of respiratory irritation.

I’d encourage you to consider why lime is needed in your barn. If the barn regularly has a strong smell of ammonia, the stall cleaning frequency and thoroughness may need to be reviewed. It’s also a good idea to evaluate the ventilation in the barn; windows, door and vents are best left open whenever possible. Sufficient air exchanges and effective stall cleaning will typically keep ammonia levels in check. Finally, consider the protein content of the horses’ diets. Research has shown that high levels of dietary protein result in higher ammonia in urine.

Karen Waite, PhD

Equine Extension Specialist

Michigan State University

East Lansing, Michigan