Barn lime, which is simply ground limestone (calcium carbonate), is generally safe for chickens. It will not burn their skin or feet the way other types of lime can. However, the word “lime” covers several very different products, and confusing them can seriously injure your flock. The most important thing you can do is make sure you’re buying the right one.
Barn Lime vs. Hydrated Lime
Barn lime goes by many names: ag lime, quarry lime, dairy lime, garden lime. Regardless of the label, these are all calcium carbonate, the same mineral found in natural limestone. It’s a mild, non-caustic powder commonly sold for horse stalls and garden soil.
Hydrated lime (calcium hydroxide) and quicklime (calcium oxide) are completely different products. Both are manufactured from limestone but chemically altered to become highly caustic. According to the University of Kentucky’s poultry extension program, these forms of lime destroy organic matter on contact. They burn the footpads of birds if left on the floor, and the dust causes severe burning of the eyes and mucous membranes when inhaled. These products should never be left where chickens can walk on them or breathe the dust freely.
The confusion happens because all three products have “lime” in the name and sometimes sit on the same shelf at a farm supply store. Always check the label for the chemical name. You want calcium carbonate. If the bag says calcium hydroxide or calcium oxide, put it back.
What Barn Lime Does in a Coop
Barn lime’s main appeal is moisture control and odor reduction. Chicken manure is wet and produces ammonia as it breaks down. A layer of barn lime on the coop floor absorbs some of that moisture and can help curb the smell. It also raises the pH of the litter, which at high enough levels can destroy the cell membranes of pathogens living in the bedding.
There’s an important tradeoff, though. Lime reduces nitrogen in litter by increasing ammonia release into the air. That means if your coop already has a noticeable ammonia smell, adding lime can actually make the air quality worse before it gets better. In a poorly ventilated coop, this is a real concern, since ammonia irritates chicken respiratory systems just as it irritates yours. Only apply barn lime when ammonia levels are low, and make sure your coop has adequate airflow.
Limitations Worth Knowing
Barn lime is not particularly effective as a pest control measure. Despite what you might hope, sprinkling it around won’t reliably kill mites, lice, or other parasites. If you’re dealing with an infestation, you’ll need a product specifically designed for poultry pest control.
It also loses much of its effectiveness when it gets wet. In a coop environment where moisture is the whole problem, this is a real drawback. Barn lime can help in drier conditions or as a base layer under fresh bedding, but it won’t rescue a chronically damp floor on its own. Fixing drainage, improving ventilation, and managing bedding are more reliable long-term solutions.
How to Apply It Safely
If you decide to use barn lime, spread a thin, even layer across the coop floor before adding your bedding material on top. Pay extra attention to spots that collect the most moisture: around waterers, beneath roosts, and in nesting boxes. Keeping the lime under the bedding rather than on the surface reduces the amount of dust your chickens breathe and minimizes direct contact with their feet.
Some coop keepers also mix lime with water to create a whitewash for coop walls and nesting boxes. This creates a coating that helps resist moisture buildup and may reduce pathogen loads on surfaces. You can brush or spray it on and let it dry completely before allowing chickens back inside.
Reapply during full coop cleanouts rather than constantly layering more on top. If you notice a strong ammonia smell after application, increase ventilation immediately.
Can Chickens Eat Barn Lime?
Calcium carbonate is the same compound found in oyster shell supplements, which are a standard calcium source for laying hens. If a chicken pecks at barn lime on the ground, it won’t be harmed. That said, barn lime isn’t formulated or sized as a feed supplement. The particle size matters for calcium absorption and gizzard function, so it’s better to offer crushed oyster shell in a separate dish for calcium needs rather than relying on whatever your hens happen to pick up off the coop floor.