Let's talk about lime
No, not the citrus fruits. The powder you scatter on gardens, and which is also widely touted as a cure for poultry parasites and wet bedding.
What is lime?
Lime is often recommended as a “fix” for external poultry parasites such as red mite, lice, fleas (particularly stickfast fleas), scaly leg mite, face mite, or scaly leg mite. While all these parasites feed on chickens, they also all spend at least some of their time in the immediate poultry environment, living in bedding materials, cracks in wood, or the floor itself.
It’s also suggested as a cure for saturated wet flooring, or to fix smelly coops.
Lime’s more common use is to “sweeten” garden or agricultural soils, to improve plant growth.
So what is lime? What can and can’t it do?
Four kinds of lime
So, ag or garden lime increases pH from acid to alkaline
What is pH?
What’s that got to do with parasites?
Is it safe?
More about the different kinds of lime
Dolomite lime
Garden lime, agricultural (ag) lime, agricultural limestone, liming
Quicklime, burnt lime
Builder’s lime, slaked lime, hydrated lime, caustic lime, pickling lime, mason’s lime, bag lime
Resources
What is lime?
For a start, we’re not talking about the smallish greenish citrus fruit :)
We’re talking about the inorganic white powder you can buy at garden or produce stores.
There are four kinds of lime, with approximately 12 different names between them, causing no end of confusion. Their chemical names are important in this context, because it’s their chemical reactions that make them useful.
Two limes are safe around living things, two are not.
The safe ones are:
CaCO3 and MgCO3 - Dolomite lime. This is fairly stable and safe to handle. even if it gets wet.
CaCO3 - Calcium carbonate. Sold as Garden lime, agricultural (ag) lime, agricultural limestone, liming. This is fairly stable and safe to handle, even if it gets wet.
The less-safe ones are:
CaO - Calcium oxide. Solid as Quicklime, burnt lime. Created by burning CaCO3 at high temperatures. This is very volatile and quite dangerous to handle. It should not be allowed to contact water except when controlled.
Ca(OH)2 - calcium hydroxide. Sold as Builder’s lime, slaked lime, hydrated lime, caustic lime, pickling lime, mason’s lime, bag lime. Created by adding water (“slake” or “hydrate” with H2O) to CaO. This is a bit volatile, but not as much as quicklime. Is used for food preservation, particularly “waterglassing” for eggs.
Of these four lime varieties, only the first two are suitable for use around animals.
So, ag or garden lime increases pH from acid to alkaline
Aglime is widely used in Australia as many of the ancient soils here tend toward acidity. Plants such as waratahs, blueberries, and camellias like an acidic soil - a pH of around 6-7.
Food plants, however, tend to prefer a relatively neutral pH - around 7-8.
The SA Department of the Environment says:
Applying aglime reduces soil acidity by neutralising acid reactions in the soil. The carbonate component reacts with hydrogen ions in the soil solution and in doing so raises the soil pH.
Using aglime to balance pH levels in soils allows growers to manage plant growth, particularly of crops.
What is pH and why is it relevant?
pH the measure of the acidity of things. It stands for “potential hydrogen”.
pH is measured by creating a liquid version of the thing we want to measure - an aqueous solution. Scientifically, it’s defined as “the negative logarithm of the hydrogen ion concentration of the solution”.
So to measure the pH of soil, it’s first dampened with plain water, then a powder sprinkled on it, which changes colour. Comparing the colour with a chart provides the relative acidity or alkalinity of the soil.
pH results are a scale, starting at 1 (extremely acid) and going to 14 (extremely alkaline or caustic). Pure water is at the centre of the scale, at pH 7.
The pH scale is logarithmic, which means that there’s a big difference between each number – a pH of 6 is ten times more acidic than a pH of 7.
Anything at either end of the scale can be extremely dangerous to living things, and can cause significant injury or death if not handled correctly.
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The human body, made up of about 60 percent water, needs a pH close to water to sustain life. Individual parts of the body may have different pH levels, however; for eg, stomach acid has a pH of 1.5−4.0; saliva is about 6.5 to 7.5, and blood is 7.35-7.45.
Any significant changes to blood pH levels in the body can cause significant illness or even death. (There’s an excellent overview of this at CompoundChem, with a really good chart showing the different proportions of the hydrogen ions at each number).
What’s that got to do with parasites and wet litter?
Good question, and somewhat the point.
As far as I’m aware, ag/garden lime is non-toxic. It doesn’t automatically kill insects on contact.
It doesn’t kill or neutralise moulds or bacteria found in wet, anaerobic litter.
But it’s not useless. It can:
change pH of soil and bedding and make it less hospitable to parasites
potentially smother and dissuade small insects
absorb liquid, as it’s a fine powder, thus helping to dry out saturated litter
change the pH of saturated litter, encouraging the good bacteria to move back in and thus reducing smell
Note: this is not proven, merely speculation.
You’ll still need to combine any use of lime with a proven anti-parasitic to handle external parasites.
Is it safe?
Kinda sorta, noting that nothing that “works” is ever entirely safe.
Ag/garden lime, and dolomite lime, are not harmful for poultry to ingest. In small quantities, they can be beneficial, as a natural source of calcium that can be absorbed in the body. Dolomite lime, in particular, may be used as the source of magnesium and calcium in poultry feeds.
However, as a fine powder, it can cause irritation to eyes, skin, throat, stomach, and gastrointestinal tract.
Further, some ag or garden lime varieties may contain crystalline silica (from quartz rocks in the ground where the lime was extracted). Long-term overexposure to crystalline silica can cause silicosis, a form of pulmonary fibrosis. Continued overexposure to silica can lead to cardiopulmonary impairment.
We thus strongly recommend the use of personal protective equipment (PPE) when handling ag or garden lime (or, for that matter, any dusty materials) in any quantity or for any period of time:
Mask
Glasses/goggles
Gloves
Long sleeves
Long pants
Boots that can be washed clean
This is particularly important if you have any sort of chronic respiratory illness, such as asthma.
All you wanted to know about all four limes
Dolomite lime
Chemical names: Dolomitic lime. Calcium carbonate and magnesium carbonate mix. CaCO3 and MgCO3.
Sourced from: crushing dolomitic limestone into a fine powder.
Main purpose: changing pH from acid to alkaline, particularly in soils, and correct magnesium deficiencies in soils. As a food additive where calcium and magnesium is required.
Good quality dolomite contains a minimum of 22% calcium and 12% magnesium. It is good for acid soils where supplies of calcium and magnesium are low, but if used constantly may cause a nutrient imbalance, because the mix is two parts calcium to one part magnesium (2:1), whereas the soil ratio should be around 5:1.
Dolomite is a stable product and safe to handle, broadly speaking. However, as a fine powder, it can cause irritation to lungs, mouth, eyes, and nose if inhaled or too much gets in there. When handling in the garden or around poultry, wear PPE when scattering and try to dig it into the soil a bit before letting the chooks back in.
Garden lime, agricultural (ag) lime, agricultural limestone, liming
Chemical name: calcium carbonate, CaCO3
Sourced from: crushing limestone, seashells, or chalk into a fine powder.
Main purpose: changing pH from acid to alkaline, particularly in soils.
Ag lime is bought in bulk (25kg bags and upwards); garden lime is in small sizes (up to about 5kg). It is otherwise the same thing.
The pH change may help reduce the smell of poultry droppings or wet rotting bedding.
As a dry powder, it can absorb liquid and help dry out wet, mouldy, nasty bedding materials such as straw.
It should be predominantly CaCO3, but may contain other chemicals depending on the original source. For example, if quartz was in the limestone, that particular mix may also contain crystalline silica (SiO2).
Aglime is a stable product and safe to handle, broadly speaking. However, as a fine powder, it can cause irritation to lungs, mouth, eyes, and nose if inhaled or too much gets in there. Versions that contain quartz may come with a silica exposure risk in sufficient quantity or over neough time.
When handling in the garden or around poultry, wear PPE when scattering and try to dig it into the soil a bit before letting the chooks back in.
Good quality lime has 37–40% calcium.
Note: as ag and garden lime is a naturally mined/crushed product, it can have inclusions based on the original source of the lime.
Examples of Materials Safety Data Sheets for different varieties of ag and garden lime:
These safety sheets are very interesting as all four contain slightly different chemical makeups. It is definitely worth looking at the ingredients list on any lime you get, so you’re aware of what’s in it.
Quicklime, burnt lime
Chemical name: calcium oxide. CaO.
Sourced from: heating limestone or calcium carbonate to 900C - 1100C. This drives off carbon dioxide, leaving behind calcium oxide.
Main purpose: when exposed to water, it expands and heats up very quickly, making it useful in industry and as a food additive (both to regulate acidity - ie change pH - and as a bread leavener).
When used in food, it has the E number E529.
Its reactive nature can cause serious burns or injury, either from the heat of the chemical reaction, or from the highly caustic (pH 12-13) product it creates. If inhaled, it can react with mucous membranes to cause internal burns and damage.
Builder’s lime, slaked lime, hydrated lime, caustic lime, pickling lime, mason’s lime, bag lime
Chemical name: calcium hydroxide, calcium hydrate. Ca(OH)2
Sourced from: slaking (mixing) quicklime with water. It produces a more stable - and much more caustic (alkaline) version of lime.
Main purpose: in the building industry . It’s a component of mortar and concrete. Food-grade versions are used in food preservation, such as waterglassing (preserving) whole eggs. Not generally used in agricultural applications.
It’s highly caustic if it gets wet, and can cause very bad chemical burns in living creatures. Can be dangerous if it gets into the damp of your eyes, nose, mouth, throat, lungs, or stomach.
Because of this caustic nature, it may have some effect against parasites such as lice or mites. Using it for this purpose needs to be weighed up against the very real risk of causing long-term injury to yourself or your animals, however.