Mold contamination is one of the most persistent problems of animal feed production. Mold can develop on grains during their growth, harvest, transport, or storage, and the mold often produces mycotoxins, toxic compounds that can damage the liver, weaken the immune system, and reduce the growth and reproductive performance of animals.
It is not always possible for feed manufacturers to totally prevent mold contamination, especially when using grain from different regions and storage conditions. What they can do is add an ingredient to the gut of the animal, which binds these toxins before they get into the bloodstream. One of the most well-known materials for just such a purpose is bentonite clay.
Let’s take it apart.
What Are Mycotoxins, and Why Do They Matter?
Mycotoxins are toxic compounds produced by some of the mold species, most often from the genera Aspergillus, Fusarium, and Penicillium. They are formed on cereal grains and other feed ingredients under heat, moisture, and poor storage conditions.
The most commonly tested mycotoxins in feed are aflatoxins, ochratoxins, fumonisins, zearalenone, and deoxynivalenol (also known as DON or vomitoxin). Each has different effects on animals, but the overall theme is slower growth, suppressed immune response, organ damage, and, in severe cases, possible reproductive problems and death.
Because mycotoxins are often present at low concentrations over large lots of grain, removal before feed processing is rarely complete. This is where binders such as bentonite come in.
How Bentonite Binds Mycotoxins
Bentonite clay is primarily composed of montmorillonite, a layered aluminosilicate mineral. Its structure provides two properties that make it useful as a mycotoxin binder.
1. Negative Surface Charge
The surface of montmorillonite particles has a negative electrical charge. Many mycotoxins, especially aflatoxins, are slightly positively charged or contain polar functional groups. These molecules are attracted to the negatively charged clay surface and held by electrostatic and adsorption forces.
2. Layered Structure with Interlayer Spaces
Bentonite has a sheet structure with interlayer spaces that can trap smaller molecules. The pockets are a good match for aflatoxin molecules, which are fairly small and planar, and this is part of the reason why bentonite is particularly good against aflatoxins in particular.
When the clay binds to the mycotoxin, it travels through the animal’s digestive tract with the clay and is excreted in the manure instead of being absorbed into the bloodstream. This means the toxin is bound and its adverse effects on the animal are significantly reduced, although technically the contamination in the original feed has not been removed (Feed Strategy, 2024).
Aflatoxins vs Other Mycotoxins: An Important Limitation
If you are going to use benefits of using bentonite clay as a binder, one thing every feed producer needs to know is that it works very well on aflatoxins, but it doesn’t work very well on other mycotoxins.
According to research published in Feed Strategy, calcium bentonite is one of the most commonly used additives to control aflatoxin contamination, but it has little to no effect on other mycotoxins such as DON, zearalenone, or fumonisins and is typically included at 0.5 to 1.0 percent of the feed.
This is important, as contamination of feed is usually not a single-toxin problem. For example, a batch of grain contaminated with Fusarium mold is likely to have DON and zearalenone as well as or instead of aflatoxins. In these cases, bentonite by itself may not be enough to give protection, and it is common practice for producers to blend it with other types of binders, such as yeast cell wall extracts or other clay minerals, to widen the spectrum of protection.
A similar strategy is described in a US Patent (No. 6,045,834, USPTO) relating to compositions for the removal of mycotoxins from animal feed. The use of a modified yeast cell wall extract in combination with a clay, such as bentonite, results in an additive binding effect, which overcomes the limitation of clay alone, binding only a narrow range of toxins.
Sodium vs Calcium Bentonite for Feed Applications
Both sodium and calcium activated bentonite powder are used in animal feeds, but for somewhat different purposes.
Calcium bentonite: The more common type of bentonite used for mycotoxin binding specifically is calcium bentonite. Feed Strategy reports research showing the role of calcium bentonite in aflatoxin control but also warns that producers should make sure diets are well fortified with essential minerals when using it, as calcium bentonite can bind certain beneficial ionic compounds as well as the toxins it targets.
Sodium bentonite has a high capacity for water absorption. In monogastric animals like poultry and pigs, sodium bentonite serves as a ‘gut sponge,’ which absorbs excess moisture from digesta. This can help with cases of wet droppings due to bacterial or osmotic diarrhea, although it is treating the symptom rather than the cause. For this purpose, inclusion rates of up to 2 % of the feed are possible.
Other Benefits of Bentonite in Animal Feed
Bentonite has other functions in feed manufacturing in addition to toxin binding, making it a useful, multi-purpose additive.
Pellets Binding
Bentonite improves the durability of feed pellets so that they can maintain their shape during transportation and handling. This reduces the amount of fines (broken pieces of pellets) and feed waste—both important for cost control and for providing animals with consistent nutrition.”
Anti-Caking
Feed ingredients tend to clump together when stored in humid conditions. The moisture-absorbing properties of bentonite keep the feed free-flowing and easier to handle in storage and in automated feeding systems.
Manure moisture management
As previously mentioned, sodium bentonite’s ability to absorb water can help firm up manure, especially in poultry operations, which helps produce drier litter and improve barn hygiene.
Regulatory Status and Safe Inclusion Rates
Bentonite is an authorized feed additive under EU legislation. According to information released by Kutch Bentoclay, the European Food Safety Authority (EFSA) evaluated bentonite as a feed additive in 2012 and recommended a maximum inclusion rate of 1 to 2 percent. Bentonite is also approved under EU regulation as a substance to reduce contamination of feed with aflatoxin B1 in pigs, poultry, and ruminants.
Typical inclusion rates reported by Feed Strategy for aflatoxin binding alone are 0.5 to 1.0 percent of calcium bentonite. Over-inclusion can affect the pelleting properties of the feed and may interfere with the absorption of some nutrients, but producers should always adhere to the inclusion levels recommended by their feed formulation specialists and the regulatory framework applicable to their market.
What This Means for Feed Producers
Calcium bentonite at recommended inclusion rates is a proven, cost-effective addition to your formulation if you are sourcing your feed ingredients from areas or storage conditions where aflatoxin contamination is a known risk. If you have other mycotoxins in your contamination profile, e.g., DON or zearalenone, bentonite alone is unlikely to be sufficient, and it would be worth considering a broader-spectrum binder strategy.
In any case, it is important to work with a feed-grade bentonite supplier that can provide consistent purity, particle size, and adsorption performance data since the binding efficiency of bentonite depends on its mineral composition and surface area.
Sourcing Feed-Grade Bentonite in India
India has deposits of bentonite mainly in the Kutch region of Gujarat. India supplies calcium and sodium bentonite for animal feed applications to domestic and export markets. Companies such as CMS Industries process bentonite for use as a feed additive providing calcium and sodium grades suitable for mycotoxin binding, pellet durability, and anti-caking applications in cattle, poultry, swine, and aquaculture feed.
When evaluating a supplier of feed-grade bentonite, ask for documentation on adsorption capacity, particle size distribution, and compliance with the applicable feed additive regulations in your intended market.
Frequently Asked Questions
- Does bentonite remove all mycotoxins from animal feed?
No. Bentonite, especially calcium bentonite, is most effective against aflatoxins. It shows no, or very limited, binding effect on other common mycotoxins, like deoxynivalenol (DON), zearalenone, and fumonisins. Bentonite is often used in combination with other binder types for wider protection, for example, yeast cell wall extracts.
- What is the recommended dosage of bentonite in animal feed?
For aflatoxin binding, calcium bentonite is generally added at the rate of 0.5 to 1.0 percent of the feed. The European Food Safety Authority has suggested a maximum inclusion rate of 1 to 2 percent for bentonite as a feed additive. Always consult your feed formulation specialist and local regulations.
- Can bentonite affect nutrient absorption in animals?
The binding effect of calcium bentonite is not immediately selective, and it may bind some good ionic compounds with mycotoxins. When calcium bentonite is used as an aflatoxin binder, diet formulators need to be certain that diets remain well fortified with essential minerals.
- Is sodium or calcium bentonite better for animal feed?
It depends on what you want. Calcium bentonite is more commonly used for aflatoxin binding specifically. Sodium bentonite absorbs more water and is often used to help control digesta moisture in monogastric animals. It is also used as a pellet binder and anti-caking agent and can help prevent wet droppings.
- Is bentonite safe and approved for use in livestock feed?
Yes. Bentonite is approved as a feed additive by the European Food Safety Authority and is registered under EU regulation for the reduction of aflatoxin B1 contamination in feed for pigs, poultry, and ruminants. As with all feed additives, it should be used within the recommended inclusion rates.
