Dairy cows that chowed down on industrial hemp produced milk that contained the psychoactive compound THC, as well as CBD and other cannabinoids, according to new research published Monday in the journal Nature Food.
The animals’ behavior changed, too: They yawned, salivated, appeared unsteady on their feet and even had red eyes, the researchers observed.
The findings raise further questions about the future viability of feeding industrial hemp to livestock, a practice that is currently outlawed in the United States because of concerns about cannabinoids making their way into the nation’s food supply chain. But hemp is nutritious, cheap and widely available, which is why farmers and ranchers are curious about any potential effects of feeding it to their animals.
“This is important, as we had no data to know to what extent cannabinoids entered the milk of dairy cows,” says Michael Kleinhenz, a veterinarian at Kansas State University who was not involved in the study, to New Scientist’s Alex Wilkins.
Hemp and marijuana plants are the same species, Cannabis sativa. But hemp has a much lower level of the cannabinoid THC, the compound typically associated with a “high” in humans. Both plants contain CBD, a nonpsychoactive compound that has become a trendy health supplement.
Legally, the U.S. government defines hemp as containing 0.3 percent or less THC. As of 2018, the government no longer classifies hemp as a controlled substance, which means it can be grown, harvested, tested, processed, transported and sold. Marijuana, meanwhile, contains higher amounts of THC and is still illegal under federal law, though many states have decriminalized it.
To get a better understanding of hemp’s effect on cattle, researchers in Germany fed hemp that contained varying concentrations of cannabinoids to ten lactating dairy cows. Half of the cows ate whole-plant hemp that contained very low levels of cannabinoids, while the other half ate hemp leaves, seeds and flowers, which had a higher cannabinoid concentration.
The researchers carefully observed the animals and analyzed their blood, milk, feces, heart rates, breathing and eating habits.
The two types of hemp affected the cattle differently. The cows that ate the low-cannabinoid hemp behaved normally and had no measurable changes in behavior. The high-cannabinoid group, on the other hand, ate less and produced less milk. Their heart rates and breathing slowed, they moved their tongues around a lot and they produced more snot and saliva. Some had wobbly gaits or stood with abnormal postures. They also had a “somnolent,” or sleepy and drowsy, appearance, the researchers note. The cows went back to normal within two days, but the scientists described the brief hemp-induced changes as “adverse effects on animal health” in a statement.
Though the researchers found THC, CBD and other cannabinoids in the cows’ milk, they didn’t test whether or how drinking that milk would affect human consumers.
“The study does not allow any conclusions to be drawn as to whether there is a health risk from consuming milk on the market,” says study co-author Robert Pieper, an animal nutritionist at the German Federal Institute for Risk Assessment, to Science’s Jack Tamisiea.
Still, the scientists did compare the amount of THC in the milk with guidelines set by the European Food Safety Authority and found that it far exceeded the level the organization has determined to be safe for consumption, especially for children. And given that hemp had a bad rap for decades, consumers are likely “not going to see CBD-enhanced milk on the shelf for a long time,” says Jeffrey Steiner, who leads the Global Hemp Innovation Center at Oregon State University and was not involved in the study, to the Washington Post’s Joel Achenbach.
Even if governments do not give farmers the go-ahead to feed their dairy cows hemp, that doesn’t rule out the possibility of feeding it to other animals that don’t produce food for human consumption, such as young lambs or cows. Past research has also found that ingesting hemp led to lower stress levels among cows, which suggests it could be useful for calming livestock during stressful situations, such as transport or weaning.