Bentonite clay and clinoptilolite zeolite share shelf space in feed mills across America. Both are regulatory-approved. Both are natural. But how they work, where they work, and what they deliver for operators and owners are fundamentally different.
PoultrySwineCattleFeed Additive
Examine the formulations of any feed mill in the United States and you will find at least one of these natural minerals; bentonite clay and clinoptilolite zeolite. Both have been approved as feed additives by regulatory authorities in the U.S. and the European Union. Both come out of the ground, require relatively minimal processing, and are sold as powders that blend into standard premix or complete feed. On paper, they look like competitors. In practice, they operate in almost entirely different dimensions of animal nutrition. Once operators understand those differences, the decision of when to use each one becomes considerably clearer.
What Bentonite Does, and Does Well
Bentonite is a clay mineral whose commercial value is built on one extraordinary physical property: it swells. When sodium bentonite contacts moisture, it can expand to fifteen times its dry volume. In a feed pelleting operation, that property is very useful. Bentonite functions as a pellet binder, holding nutritional ingredients together under the mechanical pressure of a pellet mill die, reducing fines, and improving pellet durability index scores. For mills running high-inclusion fat or high-fiber diets where binding is notoriously difficult, bentonite at inclusion rates of one to two percent is frequently the cheapest, most reliable binding aid available.
Beyond binding, bentonite's swelling capacity and high surface area give it general adsorptive properties. It has been shown to adsorb certain mycotoxins, such as aflatoxin B1, via surface binding, and it is EU-approved as a binder and anti-caking agent across all species. At commodity pricing of $80–$200 per metric ton, depending on grade, bentonite is accessible to virtually every scale of operation. For the feed mill operator whose primary concern is throughput and pellet quality, bentonite earns its place in the formulation.
Its limitations, however, are structural. Bentonite is a non-selective adsorbent: it binds things broadly rather than targeting specific molecules. It cannot regenerate. Once loaded, bentonite passes through the animal as inert waste. It produces no nutritional value. And its binding affinity for aflatoxin, while real, is moderate and uneven across the full spectrum of mycotoxins now routinely occurring in North American grain supplies.
The Architecture of Clinoptilolite
Clinoptilolite zeolite works through an entirely different mechanism. It is not a swelling clay. It is a crystalline aluminosilicate - a three-dimensional molecular cage structure with a precisely defined pore diameter of approximately 4.0 to 7.0 angstroms and a high cation exchange capacity (CEC) typically ranging from 120 to 220 milliequivalents per 100 grams. This porous mineral is selective. Clinoptilolite preferentially captures specific ionic species, including ammonium, potassium, calcium, and several heavy metals, while allowing water and other molecules to pass through unimpeded.
Clinoptilolite is not a general-purpose adsorbent. It is an ion-selective exchange medium at the molecular level, and the implications for animal nutrition are significant. The cage structure gives clinoptilolite a meaningfully different mycotoxin-binding profile from bentonite.
Bentonite Clay | Clinoptilolite Zeolite |
|---|---|
Mechanism - Surface adsorption via swelling | Mechanism - Ion-selective cation exchange |
Primary role - Pellet binding, anti-caking | Primary role - Ammonia scavenging, mycotoxin binding, gut environment |
Mycotoxin coverage - Aflatoxin B1 (moderate); limited on ZEA and fumonisins | Mycotoxin coverage - Aflatoxin B1, ZEA, fumonisin — broader spectrum |
Ammonia control - None | Ammonia control - Traps NH₄⁺ in cage structure — reduces litter and barn NH₃ |
Heavy metal binding - Non-selective, moderate | Heavy metal binding - Selective for Pb²⁺, Cd²⁺, Zn²⁺ |
Regulatory status - EU E558 — binder/anti-caking agent. GRAS-supported in U.S. | Regulatory status - EU E568 — all species; GRAS-supported in U.S. |
Cost per ton - $100–$200 (FOB) | Cost per ton - $200–$300 (FOB) |
"Clinoptilolite is not competing with bentonite on the same terms. It occupies a different functional role built around ion chemistry rather than physical binding, and performance data rather than pellet durability scores."
Where Clinoptilolite Changes the Economics
The case for clinoptilolite in a commercial feed operation is not built on pellet quality. It is built on three areas where the mineral delivers measurable, often monetizable results that bentonite does not provide.
The first is ammonia. In confined poultry and swine facilities, airborne ammonia is among the most persistent productivity drains an operator faces. At concentrations above 25 ppm, a threshold routinely exceeded in commercial broiler and wean-to-finish barns during winter months. Ammonia causes measurable reductions in average daily gain, depressed immune function, and chronic respiratory irritation that elevates mortality and veterinary costs.
Clinoptilolite, when included in the diet at one to two percent, traps ammonium ions (NH₄⁺) in its cage structure before they volatilize into the barn air. Published trials in commercial broiler operations have reported ammonia reductions of 25 to 45 percent at standard inclusion rates. For operations in regions with air quality permits or neighbor-proximity challenges, that number carries a direct regulatory compliance value that does not appear on a feed cost spreadsheet but absolutely appears in a permit renewal conversation.
40%
Reduction in litter ammonia emissions reported in commercial broiler trials
2–4%
Improvement in FCR documented in swine nursery studies at 1.5% inclusion
120+
Milliequivalents per 100g CEC — ion-exchange capacity driving performance
The second area is feed conversion ratio. Several peer-reviewed trials including controlled studies in swine nursery pigs and commercial broilers have reported FCR improvements of two to four percent at clinoptilolite inclusion rates of one to two percent of diet. The proposed mechanisms include improved gut morphology (increased villus height and crypt depth observed in histological studies), modulation of gut pH, and reduced systemic burden from ammonia and mycotoxin exposure. A two-percent FCR improvement in a 100,000-bird broiler house running six flocks per year represents a meaningful reduction in feed cost per pound of gain. This is one of the largest variable costs managed by operators.
The third area is the mycotoxin problem, which has grown considerably more complex over the past decade. North American grain surveys now routinely show multi-mycotoxin contamination events — aflatoxin co-occurring with deoxynivalenol, zearalenone, and fumonisins in the same commodity lot. Bentonite's primary efficacy is concentrated in aflatoxin B1. Clinoptilolite's binding profile, combined in some commercial products with yeast-derived components, covers a broader spectrum. For integrators purchasing grain at spot market across a broad geography, particularly in the southeastern U.S. and the corn belt, a binder with broader mycotoxin affinity is a meaningful risk management tool, not just a nutritional additive.
The Practical Decision for Operators and Owners
The most commercially sophisticated operations have stopped treating these two minerals as mutually exclusive. In broiler and swine programs where pellet quality is a feed mill priority, and mycotoxin risk is moderate, a blend (bentonite for binding function and clinoptilolite at a lower inclusion for its ion-exchange benefits) captures value from both minerals at a combined cost that remains competitive. Where ammonia compliance, FCR optimization, or a documented mycotoxin challenge drives the decision, clinoptilolite earns a standalone premium inclusion justified by performance output rather than input cost.
For owners reviewing their mineral additive program from a return-on-investment perspective, the question is straightforward: are you paying for a physical function (binding) or a biological outcome (ammonia control, gut performance, broader mycotoxin protection)? Bentonite delivers the former reliably and cheaply. Clinoptilolite delivers the latter with a specificity and mechanism that no clay mineral can replicate.
References
- EFSA FEEDAP Panel (2017). Safety and efficacy of bentonite as a feed additive for all animal species. EFSA Journal. PMC7010171. The panel assessed bentonite's safety and efficacy as a technological feed additive for mycotoxin reduction across all animal species, approving it at a maximum of 20,000 mg/kg complete feed. NCBI
- EFSA FEEDAP Panel (2025). Assessment of the feed additive consisting of bentonite (1m558i) for all animal species — renewal of authorisation (EUBA aisbl). EFSA Journal. https://doi.org/10.2903/j.efsa.2025.9553
- EFSA FEEDAP Panel (2025). Assessment of the feed additive consisting of bentonite for ruminants, poultry and pigs — renewal of authorisation (Biomin GmbH). EFSA Journal. https://doi.org/10.2903/j.efsa.2025.9263
- EFSA FEEDAP Panel (2013). Scientific opinion on the safety and efficacy of clinoptilolite of sedimentary origin for all animal species. EFSA Journal. https://doi.org/10.2903/j.efsa.2013.3039. The 2013 FEEDAP opinion concluded that clinoptilolite of sedimentary origin is safe up to 10,000 mg/kg for target species, consumers, and the environment. EFSA
- EFSA FEEDAP Panel (2025). Safety and efficacy of the feed additive consisting of clinoptilolite of sedimentary origin for all animal species — renewal of authorization. EFSA Journal. https://doi.org/10.2903/j.efsa.2025.9364. The renewal opinion confirms that clinoptilolite of sedimentary origin (1g568) remains safe for all animal species, consumers, and the environment under authorised conditions. nih
- EFSA FEEDAP Panel (2025). Safety and efficacy of a feed additive consisting of clinoptilolite of volcanic origin for all terrestrial animal species (IMERYS Talc Europe). EFSA Journal. https://doi.org/10.2903/j.efsa.2025.9780. The panel concluded that clinoptilolite of volcanic origin is efficacious as a pellet binder and anti-caking agent in feed for terrestrial animal species. nih
- Mohammadi Ghasem Abadi, M.H. & Karimi Torshizi, M.A. (2019). Effect of different types and levels of fat addition and pellet binders on physical pellet quality of broiler feeds. Poultry Science. ResearchGate. Two experiments evaluated bentonite and calcium lignosulfonate as pellet binders on PDI, pellet hardness, and pellet length in broiler diets processed under short-term conditioning with varying fat types and levels. Academia.edu
- [Meta-analysis author group] (2025). Evaluating variables affecting Pellet Durability Index (PDI) in pelleted corn-soy-based feeds for swine and poultry: A meta-analysis. Animal Feed Science and Technology. https://doi.org/10.1016/j.anifeedsci.2025.XXX. A meta-analysis of 29 published studies with 280 treatment mean observations quantified the impact of formulation and manufacturing factors — including binder type — on PDI across swine and poultry feeds. ScienceDirect
- [Author group] (2025). Impact of pellet binder on feed quality, broiler performance, carcass yield, and organ development: A Meta-Analysis. Veterinary Integrative Sciences. https://he02.tci-thaijo.org/index.php/vis/article/view/270379
- FEFAC — European Feed Manufacturers' Federation. Use of bentonite (mycotoxin binder). Sustainable Animal Feeding Strategies. https://fefac.eu/pages/sustainable-animal-feeding-strategies. Bentonite demonstrates aflatoxin B1 adsorption of 90.0–95.3% at pH 5 in vitro and is approved for ruminants, poultry, and pigs as a mycotoxin reduction additive. Fefac
- Kang, Y. et al. (2022). An in vitro study on the efficacy of mycotoxin sequestering agents for aflatoxin B1, deoxynivalenol, and zearalenone. Animals (MDPI), 12(3), 333. https://doi.org/10.3390/ani12030333. All mycotoxin sequestering agents tested achieved AFB1 binding above 92%, but most products except activated charcoal failed to adequately sequester DON and zearalenone — highlighting bentonite's narrower spectrum. MDPI
- Vekiru, E. et al. (2010). Aflatoxin toxicity reduction in feed by enhanced binding to surface-modified clay additives. Toxins (NIH/PMC). PMC3202849. Sodium bentonite demonstrated the strongest binding capacity for aflatoxin B1 among clays tested, with interlayer surfaces and hydrogen bonding identified as dominant mechanisms. nih
- Karamanlis, X., Fortomaris, P., Arsenos, G., Dosis, I., Papaioannou, D., Batzios, C., & Kamarianos, A. (2008). The effect of a natural zeolite (clinoptilolite) on the performance of broiler chickens and the quality of their litter. Asian-Australasian Journal of Animal Sciences, 21(11), 1642–1650. https://koreascience.or.kr/article/JAKO200810103447509.page. A trial of 5,200 Cobb 500 broilers showed that 2% dietary clinoptilolite significantly reduced mean litter ammonia concentration and improved growth rate compared with the basal diet control group. Korea Science
- [Author group] (2024). Impact of adding zeolite to broilers' diet and litter on growth, blood parameters, immunity, and ammonia emission. Poultry Science. https://doi.org/10.1016/j.psj.2024.XXX. Clinoptilolite traps nitrogenous metabolites including ammonium (NH₄⁺) and ammonia (NH₃), resulting in renewed interest as an economical feed and litter additive to reduce ammonia emissions in poultry houses. ScienceDirect
- [Author group] (2025). Effect of natural zeolite in diets with or without protein reduction on the performance, carcass and organ yield, and litter quality of broilers. PubMed/PMC. PMC12861144. https://pubmed.ncbi.nlm.nih.gov/41576441/. Dietary clinoptilolite at 1% of diet was found to be an effective strategy to reduce ammonia emissions from broiler litter without impairing performance or carcass yield, provided adequate protein and amino acid balance is maintained. PubMed
- Nakaue, H.S. & Koelliker, J.K. (1981). Studies with clinoptilolite in poultry. I. Effect of feeding varying levels of clinoptilolite (zeolite) to dwarf Single Comb White Leghorn pullets and ammonia production. Poultry Science, 60(4), 944–949. (Cited in multiple review papers as foundational reference for zeolite/ammonia research.)
- [Author group] (2019). Effects of clinoptilolite and modified clinoptilolite on the growth performance, intestinal microflora, and gut parameters of broilers. Poultry Science. https://doi.org/10.1016/j.psj.2019.XXX. Increases in villus height and villus height-to-crypt depth ratio were observed in the small intestinal mucosa of broiler chicks supplemented with natural and modified clinoptilolite. ScienceDirect
- Papaioannou, D. et al. (2002 & 2005). A field study on the effect of in-feed inclusion of a natural zeolite (clinoptilolite) on health status and performance of sows/gilts and their litters. Livestock Science. https://doi.org/10.1016/S0034-5288(01)00905-2. Dietary incorporation of 2–4% clinoptilolite resulted in improved performance at growing/finishing and gestating/lactating stages, attributed to its beneficial effect on nitrogen retention and protein digestibility. ScienceDirect
- [Author group] (2019). The effects of clinoptilolite administration on the appetite, the consistency of faeces and the histology of the small intestine in growing pigs. Academia/Veterinary literature. https://www.academia.edu/118950364. (Landrace × Large White crossbred trial; 2% ZeoFeed in growing pigs.)
- [Review group] (2022). Efficacy of mycotoxin binders to control mycotoxins in feeds and the potential risk of interactions with nutrient: a review. Journal of Animal Science, 100(11), skac328. https://doi.org/10.1093/jas/skac328. A literature review of 68 papers and 1,842 data points across eight mycotoxin-binding materials and six mycotoxins — including bentonite, clinoptilolite, and HSCAS — analyzed adsorption capacity differences by material and toxin class. Oxford Academic
- [Author group] (2025 meta-analysis). Evaluating zeolite stability as a mycotoxin binder in broiler chickens' growth performance: A meta-analysis. Veterinary Medicine — Mosul. https://www.vetmedmosul.com/article_187768.html. Clinoptilolite-based zeolite significantly reduced FCR and mortality rates in mycotoxin-challenged broilers; aflatoxin, aflatoxin B1, and ochratoxin A showed the highest responsiveness to zeolite supplementation. Vetmedmosul
- Dakovic, A. et al. (2016). Adsorption of the mycotoxin zearalenone by clinoptilolite and phillipsite zeolites treated with cetylpyridinium surfactant. Colloids and Surfaces B: Biointerfaces. https://doi.org/10.1016/j.colsurfb.2016.XXX. Surface-modified clinoptilolite showed measurable zearalenone adsorption increasing with higher surfactant levels, with the organozeolite requiring significantly less modifier than organobentonite for maximum ZEA adsorption. ScienceDirect
- Kemin Industries. Using aluminosilicates for mycotoxins. Technical Reference. https://www.kemin.com/na/en-ca/markets/animal/feed-quality/using-aluminosilicate-anti-caking-aids-to-minimize-impact-of-mycotoxins-on-performance. In vitro two-phase total binding efficiency modeling showed enhanced zeolite binding of fumonisin at 55.2%, T-2 toxin at 47.4%, and zearalenone at 34.1%, demonstrating broader-spectrum coverage beyond aflatoxin alone. Kemin
- [Author group] (2000). Preventive efficacy of clinoptilolite in broilers during chronic aflatoxin (50 and 100 ppb) exposure. Poultry Science (ScienceDirect). https://doi.org/10.1016/S0034-5288(00)90417-0. Clinoptilolite at 1.5% and 2.5% dietary inclusion was evaluated for its ability to reduce the deleterious pathological effects of aflatoxin in broilers from days 1 to 21 of age. ScienceDirect
- Mastinu, A., Kumar, A., Maccarinelli, G. et al. (2019). Zeolite clinoptilolite: Therapeutic virtues of an ancient mineral. Molecules, 24(8), 1517. https://doi.org/10.3390/molecules24081517. (Cited across multiple animal nutrition studies as the primary mechanistic review of clinoptilolite's ion-exchange, adsorptive, and catalytic properties in biological systems.)
- Shariatmadari, F. (2008). The application of zeolite in poultry production. World's Poultry Science Journal, 64(1), 76–84. (Widely cited foundational review covering mechanism, inclusion rates, and performance outcomes across poultry species.)