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Got THC In Your Milk? Maybe You Can…

Cow produce milk with THC when fed hemp
Written by Sarah Friedman

If cows eat cannabis, is there THC in their milk?

The question over how breast milk is affected by drug intake is big these days, what with all the prescription and non-prescription drugs flying around. The same issue technically goes for other animals, including cows; which have the designation of providing us milk. A recent study shows how cows that consume cannabis, have cannabinoids like THC and CBD in their milk. Is this okay for cows? And could this be a new way to use cannabis?

Drugs passing into breast milk

When it comes to human childbearing, there are certain issues that arise in terms of how to protect a fetus from chemicals. There is sometimes bickering over what can cross the amniotic sac and get to the baby. Likewise is the argument that a breastfeeding mom is likely to pass on the chemicals she ingests to her baby byway of breastmilk. As of yet, while mothers are often warned away from drugs like cannabis, evidence of it being damaging when consumed in breast milk is inconclusive at best. But that doesn’t mean other drugs can’t cause harm.

It’s even said that if you’re a woman breastfeeding who wants to do certain drugs, like “amphetamines, ecstasy, cocaine or heroin, you should not breastfeed for 24 hours after use.” And that for things like smoking or drinking, that breast feeding should come first. In fact, if a woman feels her breast milk is unclean, she can ‘pump and dump’, meaning pumping out a round, so that new clean milk is produced.

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It’s generally recommended not to drink or take drugs within the first month of breast feeding, and some women maintain this for the entirety of the breast feeding experience. Of course, there are so many prescriptions that we take for so many things, that these days, its sadly hard to imagine that many babies get through without exposure to something.

The reason this happens is because many compounds can pass through biological membranes, so long as they’re not too big (like insulin). The drugs are transferred from the mother’s plasma to the milk through passive diffusion across the membranes. This transfer is effected by things like protein binding, lipid solubility, and ionization. When the mother’s plasma protein binding is low and with high lipid solubility, this transfer is strongest. The other issue is that milk has greater acidity levels than plasma, which lets drugs with weak bases transfer more easily (think amphetamines and opioids).

This is the issue as seen for human mothers in our society. But it exists in another arena. We’re big drinkers of cow milk (whether it makes sense or not), and the same idea applies. If a cow is fed specific drugs, how likely are they to end up in the cow milk that we then consume? A recent study highlighted the ability for THC and other cannabinoids to be transferred to cow’s milk, when the animals are fed hemp.

The study on THC passing into cow’s milk

In November 2022, this study was published in Nature Food, called Transfer of cannabinoids into the milk of dairy cows fed with industrial hemp could lead to Δ9-THC exposure that exceeds acute reference dose. The idea was to establish if cannabinoids get transferred through animal milk (and in what amounts), when industrial hemp is used in animal feed products. In order to shine some light on the topic, this study was done by feeding cows hemp.

Researchers “collected and analyzed milk, blood plasma and feces, measured physiological parameters and observed animal behavior.” They also used “a liquid chromatography–tandem mass spectrometry-based analytical technique that ensures differentiation between Δ9-THC and Δ9-THCA in various matrices,” which “enables quantification of the cannabinoids Δ8-tetrahydrocannabinol (Δ8-THC), Δ9-tetrahydrocannabivarin (Δ9-THCV), CBD, cannabinol (CBN), cannabidivarin (CBDV) and the two Δ9-THC metabolites 11-hydroxy-Δ9-THC (11-OH-THC) and 11-nor-9-carboxy-Δ9-THC (THC-COOH).”

The data collected was then used to “develop a predictive toxicokinetic model, which can be used to simulate other exposure scenarios and to assess the transfer of different cannabinoids into cow milk when using industrial hemp as a dietary supplement for dairy cows.”

What did the study find in terms of cow health when ingesting hemp?

Researchers specifically used Holstein Friesian dairy cows, and first partially replaced their corn silage with hemp silage, which came from the whole plant and had a low cannabinoid level. This was the adaptation phase. After this, they were fed hemp silage which came from the cannabis leaves, flowers and seeds, and which contained high levels of cannabinoids. This was the experimental phase.

Cow milk is a product of what cows are fed
Cow milk is a product of what cows are fed

This experimental phase was done at two different levels. Group L was fed 0.84 kg a day for the low hemp group; and group H was fed 1.68 kg a day for the high hemp group. After this came a final phase – depuration, in which no hemp was given and the cows cleaned the hemp from their systems.

Results show that when fed up to .92kg/day from the lower cannabinoid hemp option (standard industrial hemp used in adaptation phase), there was no difference in physiological parameters or overall health issues. On the other hand, cows fed the higher cannabinoid hemp did experience effects in both experimental groups. Both feed intake (and therefore) milk production went down greatly after Day 2 with both groups. Results also showed that respiratory rate and heart rate both went down in a matter of hours for both experimental groups. With some animals, they fell enough to be considered bradypnea or bradycardia.

Changes were also seen in the animals’ behavior and physical appearance. They had greater tongue play, yawned and salivated more, had more nasal secretions, experienced reddening and prolapse of the nictitating membrane (third eye lid), and appeared tired. Some animals in the higher consumption group stood abnormally, and for longer periods of time; and walked unsteadily and carefully.

All changes to the cows lasted until about two days after the hemp feeding stopped. The hemp didn’t affect basic milk constituents like fat and lactose, nor did it affect body temperature or body weight. To be clear, these cows were not fed a normal amount of THC, even for their body sizes. They were fed approximately 86X (per their sizes) the minimum amount of THC to cause adverse effects in humans. This makes the health results a bit questionable in term of what should actually be expected. Other studies have not shown negative reactions with standard industrial hemp feed.

Cannabinoid transfer when cows are fed hemp

The cow milk was tested after hemp consumption. During both the adaptation phase and experimental phase, “measurable levels of ∆9-THC, ∆9-THCA, ∆9-THCV, CBD, CBN and CBDV in cow’s milk” were found. On the last day of the cleaning out phase, THC and CBD were still detected in the breast milk. Other cannabinoids were not detected during any of the study. When compared to corresponding blood plasma levels, delta-9 THC was found at concentrations 6-26X higher after the experimental period, whereas it was 3-5X higher for THCV, and 11-32X higher for CBD. This implies the cannabinoids can accumulate in the milk.

Not all cannabinoids seemed to accumulate though. THCA and CBDV didn’t show this, and CBN couldn’t be detected in plasma, so no comparison was made. Though urine was collected, there were some issues that essentially kept it from being evaluated and used in the data; so all information that could have come from that, is missing.

THC is naturally infused into milk when cows eat hemp
THC is naturally infused into milk when cows eat hemp

Study investigators concluded that “Our study shows that feeding cannabinoid-rich industrial hemp silage made from leaves, flowers and seeds leads to a decrease in feed intake and milk yield in dairy cows.” In terms of cannabinoids passing into milk, they go on to say that “The toxicokinetic modelling has shown that the transfer rates of the examined cannabinoids from feed to milk were less than 1%.” Let’s remember, these cows were fed huge amounts of cannabinoids like THC, so 1% is still a lot under the circumstances.

They go on, “Nevertheless, due to the high feed intake, cow’s milk reached substantial levels of Δ9-THC such that the exposure might exceed ARfD in some population groups in our exposure scenario based on the transfer properties presented here.” They also stipulate, “For other cannabinoids, in particular for CBD, which was present in high amounts in industrial hemp (and thus also in cow’s milk after feeding), the data are currently insufficient, thereby preventing an assessment of possible health risks.”


This is an interesting study which backs up what we already kind of knew, that some constituents of the cannabis plant should make it into cow milk when hemp is eaten. One of the issues with the results however, is that the cows were fed such large amounts of THC. When fed the lower THC hemp, there were no issues, indicating the likelier feed option, probably won’t cause a problem.

Regardless, it does go to show that milk can be engineered to have cannabinoids, by changing the diet of the cow. However we should remember that cows are living things, and using them to produce natural THC infused milk, brings up even more ethical issues, than the ones that come with the existence of the industry in general. Perhaps this is a good reminder of the on-the-horizon synthetic milk, which is yet another strange breakthrough in the general milk industry; though also not one without a lot of controversy.

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About the author

Sarah Friedman

I look stuff up and and write stuff down, in order to make sense of the world around. And I travel a lot too.