Dairy cows fed industrial hemp produced milk with detectable levels of the buzz-inducing molecular compound THC, according to a new study from Germany that could influence the potential uses of hemp as an ingredient in animal feed.

The dairy cows also showed behavioral changes – yawning and salivating a lot, moving a little unsteadily on their hoofs, standing in one place for a protracted period, and having a “somnolent appearance.”

The peer-reviewed study, conducted on Holstein cows in Berlin and published this month in the journal Nature Food, is one of the first major investigations of the use of industrial hemp as a potential supplement in animal feed.

For now such use is illegal under U.S. law, which does not allow THC in the food chain. But the new research comes as hemp, which has many industrial uses, continues to emerge from an agricultural exile that dates to the “reefer madness” hysteria of the 1930s.

Hemp is the common name of the plant Cannabis sativa. Humans have cultivated it for thousands of years. Its fibers are prized in rope manufacturing, among many other uses. George Washington grew it at Mount Vernon in the late 1700s, and in recent years the estate has grown it anew.

The flowers of the cannabis plant have high concentrations of delta-9-tetrahydrocannabinol – THC. That’s the molecular compound that delivers a high to someone who smokes or consumes it. Hemp with high levels of THC is called “marihuana” in the curious spelling of the federal government, and remains a Schedule 1 substance under the Controlled Substances Act of 1970.

Industrial hemp is not the pot plant cultivated by people hoping to grow their own weed. Under the Farm Bill of 2018, industrial hemp is no longer listed as a controlled substance so long as it contains no more than 0.3 percent THC.

One byproduct of that change in the law is the booming market for another hemp-derived molecular compound, cannabidiol, or CBD. That’s typically marketed for its purported health benefits. You can get a dose of it in your coffee if you go to the right cafe.

The claimed health benefits of CBD for the most part lack the imprimatur of the Food and Drug Administration. The FDA has approved only a few products derived from hemp, and has sent warning letters to some companies making scientifically hazy claims about CBD products.

As all this gets sorted out by scientists and regulators, the hemp industry continues to expand. It’s still a tiny slice of the agricultural commodities market, but that could change. Hemp could be an excellent source of animal feed if government regulators approve it, said Erica Stark, executive director of the National Hemp Association. The seeds of hemp do not contain any THC, she said, and are high in protein.

“It’s going to be such a really large market. There’s actually animal feed shortages in this country right now, ramifications of what’s happening in Ukraine, droughts and other crop failures,” Stark said.

The researchers at the German Federal Institute for Risk Assessment found no behavioral change in cows given the entire hemp plant, which contained very low levels of THC. Only when fed the portions of the hemp plant with higher THC concentrations – including the flowers and leaves – did the behavioral effects appear, according to the study.

Those effects included slower heart rate and respiration, “pronounced tongue play, increased yawning, salivation, nasal secretion formation,” and reddening of a portion of the eyes, the report states. Some animals “displayed careful, occasionally unsteady gait, unusually long standing and abnormal posture.”

The animals also ate less and produced less milk, according to Robert Pieper, head of the department of food chain safety for the institute and co-author of the new paper.

“That is a strong effect on animal health. Not a positive effect,” he said. But he did not predict how it would play out in the policy world.

Industrial hemp was gradually legalized in the U.S. through the Farm Bills of 2014 and 2018 amid a broad but patchwork easing of laws against marijuana consumption.

That legalization has regulatory limits, however. The FDA continues to view THC, CBD and other cannabinoids as contaminants in the food supply.

“You’re not going to see CBD-enhanced milk on the shelf for a long time,” said Jeffrey Steiner, director of Oregon State University’s Global Hemp Innovation Center.

Steiner, who was not part of the newly published research, has experimented on hemp as a feed supplement for dairy cows, sheep and poultry. But his team has only had authorization to study hemp since 2019, and he stressed that much more research needs to be done before the plant is likely to get regulatory approval as an animal feed.

The plant became stigmatized and caught up in racist and jingoistic ideology during the 1930s, when allegations of marijuana use were among the rhetorical attacks on Mexican immigrants. Steiner said a federal 1937 marijuana tax essentially priced hemp out of the market. During World War II, hemp was again used in the war effort, and Henry Ford even exhibited a car made partially from hemp, but the reprieve was brief and the 1970 Controlled Substances Act outlawed the plant’s cultivation.

“All during that time, hemp was stuck in the time capsule and you couldn’t do anything with it,” Steiner said. “Now, it’s a matter of catching up, letting hemp come into the market, and letting science being the basis for making decisions.”

The dairy industry will likely want to use hemp as a feed additive if it gets federal approval and is competitive with other sources of protein, said Jamie Jonker, chief science officer at the National Milk Producers Federation. The industry, he said, has struggled with rising costs of feed and energy, though some of that pressure has been relieved by high prices on milk.

Another possible use of hemp in livestock is as a stress reducer, for example when cows are being transported, said Michael Kleinhenz, an assistant professor in beef production medicine at Kansas State University. He has conducted research on steers fed hemp, and the animals tended to become calmer, he said.

“We don’t know if they have that buzz, or whatnot,” Kleinhenz said. But they do have lower levels of stress hormones, he said. The cannabinoids reduce stress, he thinks, but “we still have to figure out that mechanism in animals.”

Jonker said he has heard reports of CBD-enhanced dairy products, such as ice cream, marketed commercially in the Pacific Northwest in recent years. But any innovation in milk marketing has to be careful, he said.

“Milk has an amazing halo to it in the average person’s mind, as being pure,” Jonker said. “There’s always a cautious approach in innovation to ensure that you’re not causing image issues with that halo.”