Most people imagine New Zealand dairy cows wandering through clean, green paddocks, eating natural grass in fresh air.
It’s part of our national identity — and the foundation of our export marketing. But behind the scenes, something far less wholesome is happening across the country.
Glyphosate-sprayed pasture is being fed directly to dairy cows.
Not rarely. Not accidentally.
As some farmers have openly admitted — it’s become a normalised practice.
And the real issue isn’t only what this does to the animals.
It’s that New Zealand doesn’t routinely test milk for glyphosate or its breakdown products at all. So even if residues are there, the system is designed not to detect them.
If we want honesty and transparency in our food chain, we need to understand what this actually means for animal health — and for the people consuming the end products.
How Glyphosate Affects Cow Health
Officials like to say glyphosate “breaks down quickly” and “passes through harmlessly.” But what we do know — from established biological mechanisms, animal physiology, and real-world farm experience — paints a very different picture. When cows eat sprayed pasture or silage, glyphosate interacts with the very systems that keep them healthy.
How Glyphosate Disrupts the Rumen Microbiome
A cow’s rumen is a living fermentation chamber that depends on bacteria to break down plant fibre. Glyphosate disrupts the shikimate pathway in those microbes, tipping the entire digestive system off balance.
The effects seen in exposed herds include:
• loss of beneficial bacteria
• overgrowth of harmful pathogens
• chronic gut inflammation
• diarrhoea and digestive issues
• reduced feed efficiency
German veterinarians documented dairy herds with rumen disorders linked to glyphosate-contaminated feed, with blood tests confirming elevated levels.
When the rumen is compromised, everything else begins to unravel.
Liver and Kidney Stress from Glyphosate Exposure
The liver is the body’s detoxification centre, and the kidneys filter waste products. Both organs show measurable strain when animals consume glyphosate-treated feed.
Documented effects include:
• elevated liver enzymes
• fatty liver changes
• kidney tubule damage
• oxidative stress
These outcomes mirror what laboratory studies have shown in multiple species — yet New Zealand still assumes cows are exempt.
Mineral Deficiencies Caused by Glyphosate Chelation
Glyphosate binds essential minerals such as manganese, cobalt, zinc, copper, and iron, reducing the animal’s ability to absorb them.
Deficiencies can lead to:
• poor fertility
• weak immune response
• low B12 synthesis (rumen-dependent)
• hoof problems
• reduced growth and vitality
Mineral depletion is one of the most overlooked yet significant consequences of feeding sprayed pasture.
Reproductive Problems in Dairy Cows Linked to Glyphosate Exposure
Several studies and field reports link glyphosate exposure in cattle to:
• lower conception rates
• silent heats
• higher miscarriage rates
• weaker calves
• hormonal disruption
Fertility is often the first place nutritional and metabolic stress becomes visible.
Why Glyphosate Makes Dairy Cows More Vulnerable to Disease
Immune systems depend on a healthy gut, balanced minerals, and functional detox organs. When glyphosate affects all three, cows respond poorly to infections, metabolic stress, and calving challenges.
Farmers who avoid feeding sprayed pasture often say their animals simply perform better — even if they’re reluctant to say so publicly.
Does Glyphosate-Sprayed Grass Affect People Who Eat Offal
This is a question almost no one talks about, yet it matters. Many New Zealanders still consume offal — particularly liver and kidneys.
These are the very organs that:
• filter glyphosate
• process AMPA
• manage oxidative stress
• store or bind contaminants
Residues are far more likely to be present in detox organs than in muscle meat. Yet New Zealand doesn’t test liver, kidney, or other organ meats for glyphosate at all. Regulators’ assurances usually refer only to muscle — not the parts of the animal most biologically exposed.
If we aren’t testing the milk or the organs most likely to contain residues, how can anyone responsibly claim there is “no risk”?
Why New Zealand Doesn’t Test Milk for Glyphosate
The uncomfortable truth is simple:
because the dairy industry doesn’t want to find it.
Milk is routinely tested for:
• antibiotics
• bacteria
• somatic cell count
• added water
• fat and protein levels
But not for:
• glyphosate
• AMPA
• glufosinate
• other herbicide residues
The official reasoning is that “glyphosate use is well regulated” and “residues are unlikely.” But this is based on assumptions — not measurement. A testing programme that never checks for herbicides will always conclude that herbicides are not a problem.
If a company like Nestlé or Danone ever did detect residues, the consequences for New Zealand’s clean-green dairy brand could be enormous. And once trust is lost, it is very hard to regain.
Why Glyphosate-Sprayed Feed Puts New Zealand’s Food System at Risk
The dairy sector relies on public trust, export credibility, and the assumption that New Zealand’s food safety systems are robust. But when a widely used herbicide is:
• sprayed on pasture
• fed directly to cows
• not tested for in milk
• not monitored in offal
• not assessed for long-term animal impacts
…it’s hard to argue that the system is working as intended.
New Zealand needs transparency — not assumptions.
We need baseline herbicide testing in milk, independent research on animal exposure, and clear rules about when glyphosate can be used on pasture destined for dairy herds.
Most of all, we need honesty.
Because feeding sprayed grass to cows isn’t just an agricultural shortcut.
It’s a risk — for animal welfare, for consumers, and for the reputation we depend on.
If cows are eating it, and people are drinking it, shouldn’t we at least know what’s there?
Resources & References
We don’t need overseas studies or industry-funded reassurance to see the bigger picture. The clues are already here at home — in our own testing, in our own food, and in the gaps our regulators keep stepping around. If glyphosate is turning up in honey, cereal, bread, waterways, and children’s breakfast bowls, then what does that say about the grass our cows are eating… and the milk we’re told is “safe”?
These articles help fill in the missing pieces of the puzzle — the pathways into our food chain, the biological effects we’re not measuring, and the uncomfortable questions New Zealand still refuses to ask.
Peer-Reviewed Studies in Dairy Cattle
Influences of Glyphosate Residues in Dairy Cow Rations
(Heymann et al., 2023 — PLOS ONE)
This peer-reviewed study on pregnant dairy cows found DNA damage, altered blood chemistry, and functional immune changes — and even detected effects in their offspring. It confirms that glyphosate-contaminated feed isn’t biologically inert, especially during early gestation.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0286995
Excretion Pathways and Ruminal Disappearance of Glyphosate
(Journal of Dairy Science, 2016)
Industry-aligned research showing that glyphosate is ingested, metabolised in the rumen, and excreted in urine and feces. Even studies that conclude “no toxicity” still demonstrate that glyphosate interacts with rumen microbes and passes through cows — directly contradicting claims that it “doesn’t accumulate” or “passes harmlessly.”
https://www.journalofdairyscience.org/article/S0022-0302(16)30187-4/fulltext
Effects of Glyphosate Contamination in Dairy Cow Diet
(Jandee et al., 2025)
A controlled feeding trial in lactating cows showing altered nutrient balance, shifts in digestibility, and changes in blood chemistry when glyphosate is present in their ration. A useful reminder that metabolic stress does not require high doses — just repeated, low-level exposure.
https://kasetsartjournal.ku.ac.th/abstractShow.aspx?param=YXJ0aWNsZUlEPTg2MTR8bWVkaWFJRD05MzE2
Contextual and Mixed-Quality Evidence
Glyphosate in Livestock: Feed Residues and Animal Health
(Vicini et al., 2019 — Journal of Animal Science)
An industry-aligned review acknowledging that glyphosate residues in livestock feed are widespread but arguing that toxicity is minimal. Useful as evidence of how regulators and industry frame the issue — and how often they rely on the absence of testing rather than the presence of data.
URL: https://academic.oup.com/jas/article/97/11/4509/5565412
Detection of Glyphosate Residues in Animals and Humans
(Krüger et al., 2014)
Veterinarians at the University of Leipzig reported glyphosate residues in dairy cows, organs, and urine. The findings are valuable, but the PDF now sits on a predatory publisher’s website, so it is included only as a reference point, not a recommended source.
URL: https://www.hilarispublisher.com/open-access/detection-of-glyphosate-residues-in-animals-and-humans-2161-0525.1000210.pdf
Investigations on Glyphosate Herbicide Impact on Ruminal Metabolism
(Riede et al., 2016)
An in-vitro rumen simulation study showing microbial shifts when glyphosate is introduced. While not a live-animal trial, it adds mechanistic insight into how glyphosate could interfere with rumen fermentation.
URL: https://academic.oup.com/jambio/article/121/3/644/6717318
Together, these studies show a pattern regulators never acknowledge: glyphosate doesn’t simply “pass through” cows. It interacts with their rumen, blood, metabolism, and even their offspring — yet New Zealand still doesn’t test the one thing families consume daily: milk.
Together, these studies show a pattern regulators never acknowledge: glyphosate doesn’t simply “pass through” cows. It interacts with their rumen, blood, metabolism, and even their offspring — yet New Zealand still doesn’t test the one thing families consume daily: milk.
Related Articles
How Glyphosate Gets Into Our Food
A clear explainer of how pre-harvest spraying and fed crops introduce glyphosate into the food chain.
https://nomoreglyphosate.nz/how-glyphosate-gets-into-our-food/
If New Zealand Tested for Glyphosate, What Would They Find?
Looks at overseas residue data and NZ’s lack of testing, then asks what a proper national survey might reveal in everyday foods like cereals, bread and snacks.
https://nomoreglyphosate.nz/if-new-zealand-tested-for-glyphosate/
What Glyphosate Is Doing to Your Microbiome
Explores how glyphosate affects gut health — relevant to rumen function and cow health.
https://nomoreglyphosate.nz/glyphosate-microbiome-impact/
Death by a Thousand Cuts: Chronic Low-Level Chemical Exposure
Connects the dots between repeated low-dose exposure and long-term health effects in both animals and humans.
https://criticalmindshift.com/death-by-a-thousand-cuts-chemical-exposure/
When you start connecting these dots, a pattern emerges — not of panic, but of unanswered questions. We test the foods that are convenient to test, we measure what fits the narrative, and we quietly ignore the rest. Yet the biology doesn’t care about regulatory blind spots. Neither do cows. Neither do our children.
If this is what we already know about glyphosate in our food system… imagine what we’d learn if New Zealand finally tested the one thing we’ve avoided all along: our milk.
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