Cows fed waste hemp from the cannabis industry produce the psychoactive compound THC in their milk and have altered breathing and heart rate and stand still for ages yawning
14 November 2022
Dairy cows that eat leftover hemp from the cannabis industry seem high to the point of illness and have potentially unsafe levels of the psychoactive compound tetrahydrocannabinol (THC) in their milk.
More hemp is grown every year to produce flowers rich in THC and cannabidiol (CBD) for places where selling or consuming cannabis is legal. Much of the plant is thrown away, so people have suggested using it in animal feed to avoid waste. But no one knew what effect this might have if the levels of psychoactive compounds in the hemp were still relatively high.
“There is this lack of information about the health effects of cannabinoids and the putative transfer into food of animal origin,” says Robert Pieper at the German Federal Institute for Risk Assessment.
Pieper and his colleagues measured this transfer by feeding five cows a hemp mixture naturally low in cannabinoids for six days and another five a mix that had high levels.
When they measured the milk from the high-concentration group using mass spectroscopy, they found high levels of several cannabinoids, including delta-9-THC, one of the most abundant psychoactive compounds in cannabis. If a normal amount of this milk was drunk by someone, they would receive a dose of THC where there could be “appreciable health risks” according to guidelines from the European Food Safety Authority, says Pieper.
“This is important, as we had no data to know to what extent cannabinoids entered the milk of dairy cows,” says Michael Kleinhenz at Kansas State University College of Veterinary Medicine. While conclusions can’t be drawn from the data itself, it will be useful for government agencies looking to see whether hemp can be used as animal feed, he says.
Pieper and his team also found that the cows acted markedly different when fed with the high-concentration feed, yawning, appearing sleepy and standing for unusually long periods in the same posture, as well as having abnormally slow breathing and heart rates – effects that are typically only seen in the course of serious illnesses.
It is unclear which elements of the industrial hemp were causing these behavioural changes, says Pieper, because the hemp contained many different cannabinoids.
He doesn’t think the term “high” should be used for the cows, though, because it describes a whole series of physiological and psychological changes in humans and we don’t know what the cows are feeling. Some observations, such as sleepiness, could also be attributed to the effect of CBD, he says.
Journal reference: Nature Food, DOI: 10.1038/s43016-022-00623-7
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