What is Glyphosate? The Dangerous Hidden Ingredient in Your Horse Feed

November 2, 2023

By Sarah Griffiths, DCH

As many of you work with me know, I’m a broken record when it comes to the topic of glyphosate. I wanted to dedicate and article to this important subject to highlight the reasons to take glyphosate ingestion seriously. It is only one of many harmful herbicidal chemicals that can be present in your horses’ feed but it may be one of the most studied in terms of it’s negative health impacts on humans and animals. The scary part is that this chemical, despite its many negative effects, does not need to be listed as an ingredient in the feed products you’re purchasing or the food you purchase for yourself. It can be hard to navigate unless you understand how the commercial agricultural industry works. This article is about protecting your horses’ health but it’s also about our own health and the health of our planet. The research citations in this article may shock you but they are important for informed decision making.

What is glyphosate?

Glyphosate is a chemical that was first synthesized in 1950 by Henry Martin, a Swiss chemist, and was later patented as a chemical chelator in 1964 by Stauffer Chemical Co. (Monsanto). Monsanto was also the creator and distributor of Agent Orange, used extensively in the Vietnam War as a chemical weapon. Glyphosate was discovered to be able to chelate (bind to) minerals such as calcium, magnesium, manganese, copper and zinc. It is also patented as an antibiotic and antifungal agent. It was introduced to the agricultural market in 1974 under the name Roundup as an herbicide and desiccant for wheat. Then in 1996, Monsanto Co. introduced the first bioengineered crop: genetically modified/Round-Up resistant soy. From this point forward, industrial use RoundUp use increased year over year with more genetically modified crops being introduced. In the US alone, 300 million pounds of glyphosate are sprayed on farmland every year.

In Sept of 2021, Health Canada increased the safe allowable spraying limit by 2 and 3 x the previous limits for peas, beans and tree nuts. This brings our allowable use in Canada up to higher levels that what even the US allows to be prayed. Weeds have become resistant to these chemicals and need to be sprayed in higher concentrations to be killed. But the environmental impacts are dire as you’ll see below. The Canadian government claims to be pro-environment but these actions do not reflect that given the affects on our soil, water, air systems and the health of humans and animals.

What ingredients contain glyphosate?

As mentioned above, soy was the first crop to be genetically modified and now all soy grown in the USA and Canada is genetically modified (GMO) and “Roundup Ready”. Other crops that are widely genetically modified to withstand Roundup include wheat, corn, beans, peas, sugar beets, canola, cotton, flax, alfalfa, barley, and tree nuts.

If you review the ingredients in your feed bags, you will most likely find one or more of these crops are included. Unfortunately, glyphosate does not need to be listed as an ingredient in your feed. The only way to avoid it is by purchasing non-GMO and certified organic ingredients. Even then, organic certifications do not completely eliminate the possibility of glyphosate residue in your feed.

There are many other crops that are sprayed with glyphosate so it’s important to educate yourself so you can avoid it when you are purchasing food for yourself and your family (human and animal!)

Environmental Impacts of Glyphosate.

Glyphosate is a water soluble chemical that does not biodegrade easily in soil. In laboratory testing, biodegradability time was favorable but when testing was done in the field, several factors impeded bioavailability including the presence of aluminum, iron, manganese and zinc. It can bind to all of these metal and remains fixed in the soil for up to one year depending on soil composition. (1) A 2020 study showed that even in cleaner areas like Nova Scotia, rivers are contaminated with aluminum and affecting the salmon populations there. (2) The addition of glyphosate along with aluminum makes for an even larger problem for aquatic life.

Another factor in biodegradation is soil microbes and fungus. Since glyphosate is a patented antibiotic and herbicide, it can render the soil sterile when sprayed regularly and in the absence of a microbial and fungal community, the glyphosate remains fixed. (1)

Early claims were made that glyphosate does not leech into groundwater but since these initial claims were made, other studies have shown that it can leach into groundwater and affect aquatic microbial communities. (1) At the rate this chemical is being sprayed, there is significant risk to our ecological water systems. Even back in 2002, 51 midwestern US streams were tested and found to contain glyphosate. (3)

Glyphosate has also been found to exist in both the air we breathe and in rainfall, further debunking claims from producers of glyphosate that it does not run off into the environment. (4)

The Health Impacts of Glyphosate.

If the aftermath of the run-off from glyphosate residue can affect our environment in these major ways, think of the implications when it comes to human and animal health with direct exposure from ingestion. We are all eating and drinking this chemical on a daily basis (even those of us who eat 100% clean, certified organic plants and animals) we are still exposed to this chemical as a result of environmental contamination.

In 2015, the University of California San Francisco found that 93% of urine samples tested (131 people) contained glyphosate. (5) In 2020, Bayer (who purchased Monsanto in 2018) settled litigation claims that glyphosate causes cancer (in particular non-Hodgkin’s lymphoma). It has currently paid out $10 billion to 95, 000 cases and still faces litigation from 30, 000 more cases. (6)

Glyphosate causes dysbiosis of the gut bacteria since it’s a patented antibiotic. It can also cause neurological changes. (7) Since gut disease, colic and neurological disease are some of the most common diseases in horses, up to and including causes of death, it is vital that you do everything you can to get glyphosate out of your horse’s life.

Equine health studies by researcher and glyphosate expert, Dr. Anthony Samsel, have revealed that glyphosate-sprayed feed can be tracked from the feed into the all tissues of horses, including the hoof tissue, causing degeneration of the hoof keratin. In his study, urine and manure were high in glyphosate. Blood was also contaminated and circulated through all body tissues, including across the blood-brain barrier. Human scleroderma was also studied in humans by the same scientist and their defective fingernails were found to be contaminated with glyphosate as well. (8) His paper on the far-reaching implications of how glyphosate can be mistakenly written into protein synthesis in mammals was published in 2016. (9) His research and other scientific papers, show that glyphosate is most likely involved in the increased development of diabetes, obesity, Celiac disease, asthma, chronic obstructive pulmonary disease (COPD), pulmonary edema, adrenal insufficiency, hypothyroidism, Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), Parkinson’s disease, prion diseases, lupus, mitochondrial disease, non- Hodgkin’s lymphoma, neural tube defects, infertility, hypertension, glaucoma, osteoporosis, fatty liver disease, chronic urinary disease, kidney failure and cancer. (10) (11) (12)

For more information on the environmental and health implications of glyphosate, check out triple board-certified specialist Dr. Zach Bush’s video here. And, if you’d like to explore more on this subject, there are hundreds of peer-reviewed papers available online about its harmful effects on people, animals and our environment.

Nutrient Deficiencies Associated with Glyphosate

Glyphosate works by blocking a metabolic pathway in plants called the Shikimate pathway. This stops the plant from being able to produce certain amino acids (the building blocks of proteins and our DNA sequences) as well as folates (B vitamins). The ingestion of these plants versus naturally-grown versions of that plant means that your horse may be lacking in important amino acids and folates. Glyphosate also alters the gut microbiome and chelates minerals out of the body, leading to further reduction in the production of B-vitamins (made by the gut microbes) and stripping important minerals out of the body. (13) (14) (15) I must also mention that most of the crops that are part of big agriculture and being fed to horses are completely species-inappropriate forms of food for horses.

How Can You Eliminate Glyphosate from Your Horses’ Diet?

It’s surprisingly easy to eliminate glyphosate from the diet if you know what to look for. Here’s your checklist for doing so:

  1. Eliminate extruded feed and any conventionally-grown grain or legume crops which includes wheat, corn, soy, lentils, flax, and sugar beets.
  2. Seek out certified organic or non-GMO feed sources, often sourced from Europe where glyphosate regulations are much more strict.
  3. Never use herbicide anywhere near grazing fields and ideally, never spray glyphosate on your property.

How Can You Protect Your Horse from the Harmful Effects of Glyphosate?

There are some easy ways ensure that you are minimizing the effects of environmental exposure to glyphosate, since it still exists residually in our land, water and air. Provide the following to your horse:

  1. Use gut-protective supplements including probiotics and the ingestion of dirt from natural environments (where trees grow) which replenishes the microbiome and decreases gut lining inflammation.
  2. Use gut-protective herbs including marshmallow root, licorice root and aloe vera.
  3. When it comes to forage, don’t feed a mono diet. Offer several no-spray hay sources to increase the variety of fibres the microbiome has access to. Be careful where you source alfalfa from since it is a heavy offender when it comes to glyphosate residue.
  4. Herbs are prebiotics too! Feed a variety of herbs including dandelion, red clover, dried nettle, rose hip, meadowsweet, greater plantain, raspberry leaf and other equine-specific herbs. Ideally, your horse can have access to live plants in a field but if they can’t, be sure to provide a rotation of dried herbs to their diet. Stay tuned for my cheat sheet e-book which will show you how to use nutritive herbs in rotation to give your horse all the benefits. (release date Nov 15, 2023)
  5. Non-GMO/molasses-free beet pulp is a great prebiotic fibre that also contains a high calcium content; a mineral that is often hard to balance in equine diets and can be disrupted by glyphosate ingestion.
  6. Medicinal mushrooms and liver-supportive herbs are a wonderful addition to provide antioxidants and apoptogenic properties to your horse’s diet. Antioxidants and adaptogens can help you horses’ immune system deal with toxic intake and inflammation. Include a rotation of chaga, lion’s mane, turkey tail, reishi, ashwaganda, milk thistle, barberry and greater celandine.

I hope this article helps you to consider the full impacts of glyphosate on your horses’ health and why it should be eliminated from all equine diets, and humans too!


  1. Intech: Herbicides: Properties, Synthesis and Control of Weeds, 2011
  2. European Geosciences Union: Ionic aluminum concentrations exceed thresholds for aquatic health in Nova Scotian rivers, even during conditions of high dissolved organic carbon and low flow, 2020
  3. US Geological Survey: Glyphosate herbicide found in many midwestern streams, 2019
  4. Environmental Toxicological Chemistry: Occurrence and fate of the herbicide glyphosate and its degradate animomethylphophonic acid in the atmosphere, 2011
  5. Ecowatch: Glyohosate found in urine of 93% of Americans tested, 2016
  6. New York Times: Roundup maker to pay $10 billion to settle cancer suits, 2020
  7. Neurotoxicology: Gut microbiota and the neurological affects of glyphosate, 2019
  8. Video: Dr. Anthony Samsel on glyphosate in keratin, 2017
  9. Journal of Biological Physics and Chemistry: Glyphosate pathways to modern disease V: amino acid analogue of glycine in diverse proteins, 2016
  10. Scientific Reports: Low-dose exposure of glyphosate-based herbicides disrupt the urine metabolome and its interaction with the gut microbiota, 2021
  11. Interdisciplinary Toxicology: Glyphosate, pathways to modern diseases 2: Celiac sprue and gluten intolerance, 2013
  12. Journal of Biological Physics and Chemistry: Glyphosate, pathways to modern diseases 4: cancer and related pathologies, 2015
  13. Plant Physiology: Perturbations of amino acid metabolism associated with glyphosate-dependant inhibition of Shikimic acid metabolism affect cellular redox homeostasis and alter abundance of proteins involved in photosynthesis and photorespiration, 2011
  14. Surgical Neurology International: Glyphosate, pathways to modern diseases 3: Manganese, neurological diseases and associated pathologies, 2015
  15. Entropy: Glyphsate’s suppression of cytochrome P450 enzymes and amino acid biosynthesis by the gut microbiome: Pathways to modern diseases, 2013