Chicken and eggs are among the most trusted staples in our kitchens.
They’re symbols of simplicity, nourishment, and affordability. But behind every carton of eggs and every roast chicken on the dinner table lies a hidden risk that few consumers ever consider: glyphosate, better known as Roundup®.
A new peer-reviewed review published in the World’s Poultry Science Journal (August 2025) shines a stark light on how Roundup —the world’s most widely used weedkiller—permeates the poultry production system. From genetically modified soy and maize feed to residues in eggs and meat, glyphosate and its toxic breakdown product AMPA don’t just touch crops—they infiltrate the very animals we depend on for food.
The review reveals a cascade of consequences: gut microbiome disruption, liver and kidney toxicity, reproductive harm, oxidative stress, and even embryonic development defects in poultry. The findings raise an uncomfortable but urgent question for consumers in New Zealand and beyond: if Roundup weakens the health of the birds themselves, what does that mean for the humans who eat them?
Glyphosate in the Poultry Supply Chain
Glyphosate isn’t just sprayed on fields to control weeds. In modern poultry production, it enters the food chain in multiple ways. The largest pathway is through genetically modified (GM) soy and maize — crops engineered to withstand heavy glyphosate spraying. These crops dominate global feed supplies, meaning chickens raised for both meat and eggs are routinely consuming glyphosate residues.
Once ingested, glyphosate and its breakdown product, aminomethylphosphonic acid (AMPA), don’t simply pass through the bird. Research shows they can accumulate in tissues, including the liver, kidneys, muscles, and even the yolks of eggs. In other words, what begins as a herbicide applied to crops can eventually reach consumers’ plates in the form of contaminated chicken and eggs.
Compounding the risk, poultry are exposed not just to glyphosate residues in feed but also to commercial formulations like Roundup®, which contain additional chemicals that amplify toxicity. These products often include undisclosed adjuvants like polyethoxylated tallow amine (POEA), which can amplify toxicity well beyond glyphosate alone. Regulators typically assess glyphosate in isolation, leaving these real-world mixtures largely unaccounted for in safety reviews.
This hidden pathway raises an uncomfortable truth: Roundup was designed as a field herbicide, yet research shows it doesn’t remain there. Through feed, water, and bioaccumulation in animal tissues, it becomes part of the poultry production cycle — and by extension, part of the human diet.
Health Impacts on Poultry
The new review highlights a troubling reality: glyphosate exposure doesn’t just affect weeds, it directly undermines the health and performance of poultry. Whether through contaminated feed, water, or bioaccumulated residues, the effects ripple through every stage of a bird’s development.
Gut Health and Immunity
Glyphosate disrupts the delicate balance of the gut microbiome, reducing beneficial bacteria while allowing harmful strains to thrive. In chickens, this translates into poorer nutrient absorption, weaker digestion, and a compromised immune system — making flocks more vulnerable to disease outbreaks.
Liver and Kidney Toxicity
Research shows that glyphosate residues accumulate in vital organs such as the liver and kidneys. Histopathological studies in chickens reveal tissue damage, enzyme disruptions, and biochemical imbalances that impair organ function. These changes don’t just affect bird health — they also raise questions about the quality and safety of the meat and eggs that reach consumers.
Oxidative Stress
Glyphosate and its breakdown product AMPA trigger oxidative stress, a process that damages DNA, proteins, and cell membranes. In poultry, this oxidative burden can weaken eggshells, slow organ growth in embryos, and contribute to long-term health decline.
Reproductive Harm
Studies of roosters and breeding hens show that even low-level, chronic exposure to glyphosate can reduce testosterone, impair sperm quality, and alter reproductive tissue. In hens, exposure has been linked to weaker eggshells, reduced hatchability, and embryos with developmental abnormalities. These effects go beyond productivity losses — they point to deeper systemic damage.
Growth and Productivity
Glyphosate-exposed poultry often show slower weight gain, reduced feed efficiency, and diminished performance. Residues have been detected in egg yolks, muscles, and liver tissue, directly undermining both the birds’ health and the end product on the table.
Taken together, the evidence paints a clear picture: glyphosate exposure weakens poultry from the inside out. What is marketed as a harmless “field herbicide” like Roundup® becomes an unseen stressor that impacts not just animal health, but the food security and safety of consumers who depend on poultry products every day.
Wider Environmental & Human Health Concerns
The findings on poultry don’t exist in isolation. What happens in chickens is a warning sign for wider risks across ecosystems and human health. Glyphosate — and commercial products like Roundup® — are not easily contained. Once released into the environment, they persist in soil, water, crops, and the animals that consume them.
Environmental Persistence and Biodiversity
Glyphosate’s widespread use leaves residues that linger long after application. Soil microbiota — the living network that underpins fertility — can be disrupted, while aquatic systems accumulate residues that affect fish, amphibians, and invertebrates. Declines in biodiversity, from pollinators to soil organisms, have been consistently linked to glyphosate-based herbicides.
Bioaccumulation and the Food Chain
Poultry are just one example of how glyphosate residues travel through the food web. When residues accumulate in eggs, meat, and organs, they create a direct pathway of exposure for consumers. This is not just theoretical: studies have already found glyphosate and AMPA residues in conventional eggs bought at grocery stores.
Health Parallels in Humans
The same mechanisms observed in poultry — oxidative stress, disruption of the cytochrome P450 system, endocrine interference, liver and kidney toxicity — have also been documented in mammalian studies, including humans. The International Agency for Research on Cancer (IARC) has classified glyphosate as “probably carcinogenic to humans,” while regulatory agencies remain divided. But the growing body of evidence points to risks that regulators can no longer afford to dismiss.
The Bigger Picture
When glyphosate undermines the health of the animals we eat, the risks don’t stop at the farm gate. They spill over into human diets, public health systems, and environmental stability. The poultry review is a reminder that glyphosate’s impact is systemic — it doesn’t just target weeds, it destabilises ecosystems, food animals, and potentially human health itself.
The Regulatory Blind Spot
One of the most striking issues raised in the poultry review is the gap between scientific evidence and regulatory oversight. Despite decades of use and mounting studies linking glyphosate to a wide range of harms, risk assessments continue to underestimate its dangers.
Focus on Pure Glyphosate, Not Roundup®
Regulators often evaluate glyphosate in isolation, testing the “active ingredient” under controlled conditions. But in real-world agriculture, poultry and people are exposed to glyphosate-based herbicides (GBHs) like Roundup®, which contain co-formulants and surfactants designed to boost penetration. Research shows these mixtures can be far more toxic than glyphosate alone, yet they remain largely ignored in safety reviews.
Short-Term, Not Long-Term
Current testing protocols emphasise acute toxicity — what happens in the hours or days after exposure. The poultry review highlights the much more serious problem of chronic, low-level exposure: oxidative stress, endocrine disruption, organ damage, reproductive harm, and bioaccumulation. These are precisely the kinds of effects that existing regulatory frameworks overlook.
Divided Classifications
While the International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans,” agencies like the U.S. EPA and European Food Safety Authority (EFSA) have continued to downplay the risks. This disconnect leaves consumers and the very animals we rely on for food exposed, while industry-friendly interpretations win out over precautionary action.
The Cumulative Risk Problem
Regulators also fail to consider the cumulative effects of glyphosate alongside other agricultural chemicals. Poultry — and humans — are rarely exposed to just one chemical at a time. The combined burden of pesticides, veterinary drugs, and environmental contaminants creates a cocktail effect that current frameworks are ill-equipped to measure.
The end result is a system that underestimates the true risk, offering consumers and farmers false reassurance. The poultry review makes it clear: until regulators acknowledge the synergistic toxicity of real-world formulations, the public remains unprotected.
The Organic Alternative
If glyphosate exposure in poultry production highlights what’s broken, certified organic farming offers a glimpse of how things could be different. Unlike conventional systems that depend on glyphosate-tolerant GM feed, certified organic poultry operations are required to use feed free from synthetic herbicides and pesticides. This distinction is critical, because overseas testing has shown that residues can still appear in “organic” products due to spray drift, contaminated supply chains, or weak certification enforcement.
Certified organic systems don’t just prohibit glyphosate and Roundup® — they build soil health, protect biodiversity, and emphasise preventive animal care, reducing the risk of contamination in the first place. While no system is perfect in a world saturated with chemicals, certified organic remains the strongest framework we have for keeping glyphosate out of the food chain.
Healthier Birds, Safer Food
Research comparing conventional and organic systems shows that poultry raised on organic feed have stronger immune systems and lower risks of antibiotic-resistant infections. In practice, however, residues have still been detected in some products marketed as ‘organic’ overseas — often due to spray drift or contamination in supply chains. That’s why Certified Organic standards matter: they remain the most reliable framework for keeping glyphosate and Roundup® out of the poultry production system.
Protecting the Environment
Certified Organic practices go further than banning glyphosate-based herbicides like Roundup®. They focus on building soil health, protecting waterways, and supporting biodiversity. By avoiding synthetic inputs altogether, certified systems reduce the risk of contamination from chemical drift and runoff — a problem that conventional farming continues to ignore.
Economic and Social Benefits
While Certified Organic poultry products often cost more at the checkout, the long-term savings come from elsewhere. Healthier birds and cleaner production systems mean fewer hidden costs for society — from healthcare expenses linked to pesticide exposure, to environmental remediation. In other words, certified organic standards help ensure that consumers aren’t unknowingly subsidising the damage caused by industrial agriculture.
A Safer Path Forward
Research comparing conventional and organic systems consistently shows benefits for animal health and food safety. But overseas experience has revealed that simply labelling something “organic” is not always enough, as residues can still appear through drift or contamination. That’s why Certified Organic frameworks, with their enforceable rules and audits, are essential. They remain the most reliable safeguard for keeping glyphosate out of the poultry system — and by extension, off our plates.
Organic is not a luxury — it’s a practical pathway to protect animal health, human wellbeing, and the environment we depend on.
Beyond the Barnyard
The new poultry review leaves little room for doubt: glyphosate — whether in feed, water, or commercial products like Roundup® — is undermining the very animals we depend on for food. From gut disruption to reproductive harm, the science shows that what begins as a “weedkiller” doesn’t stay in the field. It travels into chickens, eggs, and ultimately the human diet.
For New Zealand, the lesson is clear. We cannot continue to treat glyphosate as an invisible background chemical in our food system. Regulators may debate classifications, but the evidence is mounting that poultry health, consumer safety, and environmental stability are all being compromised.
The path forward is not complicated. Stronger independent testing of poultry products, stricter oversight of feed imports, and a transition toward Certified Organic systems are practical steps we can take right now. What is missing is the political will to acknowledge the risks and act on them.
As consumers, we are not powerless. Every choice we make — from asking where our food comes from to supporting glyphosate-free and certified organic producers — helps shift the system. The real question is: how long will we accept a food chain where toxic herbicides silently travel from crop to chicken to consumer before demanding change?
Resources & References
Before drawing conclusions, it’s worth exploring the wider research that underpins these findings. The studies and reviews below provide a deeper look into glyphosate’s role in poultry production, its impacts on animal and human health, and the broader regulatory and environmental context.
Glyphosate in poultry production: health risks, toxicity, and environmental impact.
World’s Poultry Science Journal.
Fathi, M. et al. (2025).
Peer-reviewed review analysing the biochemical, toxicological, and ecological effects of glyphosate (Roundup®) in poultry. Highlights organ toxicity, gut disruption, reproductive harm, and the shortcomings of regulatory oversight.
Potential toxic effects of glyphosate and its commercial formulations.
Food and Chemical Toxicology, 84, 133–153.
Mesnage, R. et al. (2015).
Review showing that glyphosate-based herbicides (GBHs) are more toxic than glyphosate alone due to adjuvants like POEA.
Glyphosate Monograph 112: Evaluation of five organophosphate insecticides and herbicides.
International Agency for Research on Cancer (IARC). (2015)
The WHO’s cancer research body classified glyphosate as “probably carcinogenic to humans,” sparking global debate and regulatory controversy.
Environmental and health effects of the herbicide glyphosate.
Science of the Total Environment, 616–617, 255–268.
Van Bruggen, A.H.C. et al. (2018)
Comprehensive review of glyphosate’s impacts on soil health, microbiota, biodiversity, and long-term human health risks.
Read study
No More Glyphosate NZ – Related Articles
Why Glyphosate Isn’t Just a Weed Killer — It’s a Public Health Issue
Exploring how glyphosate affects far more than weeds, including the food we eat and the health of future generations.
Glyphosate and Hormone Disruption: What We Know So Far
Review of emerging evidence that glyphosate interferes with the endocrine system.
Why Raising MRLs Threatens Public Health
Analysis of New Zealand’s proposal to raise glyphosate residue limits on staple crops and what it means for consumers.
These resources make one thing clear: glyphosate-based weedkillers such as Roundup® aren’t just a farm input — they thread their way from soil and feed into animals, food, and ultimately people. The science is building, but so too is the silence of regulators. If even poultry, one of the most intensively studied food animals, shows such vulnerability, what does that say about the wider food system we’ve built?
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