Hemp-Fed Cows Get Buzzed, Study Finds, but Will Humans Who Drink Their Milk?

Do cows that consume cannabis act goofy, get the munchies and spend more time lolling about with their stoned buddies?

It may sound like the beginning of a bad joke, but German researchers seeking to understand the effects of feeding dairy cows THC, the psychoactive compound found in industrial hemp, made a few intriguing discoveries, according to a study published this week in the journal Nature Food.

Compared with cows that received the usual diet of corn and hay, the hemp-fed Holsteins were more chilled out, salivated and yawned more often, and frequently engaged in whimsical tongue play, the study found. They also spent more time lounging around the barn as they chewed their cud and ruminated the universe.

They did not, however, exhibit a proclivity for binge eating.

Although the behavioral changes were noteworthy, they were in some ways the unintended consequences of an experiment by researchers at the German Federal Institute for Risk Assessment, who were seeking to learn how THC-laden hemp might affect dairy production. The scientists also wanted to know whether THC, short for tetrahydrocannabinol, could find its way to humans through milk.

Those questions are especially pertinent to American hemp growers, who have struggled to find an outlet for the roughly 24,000 tons of organic matter leftover once cannabinoid compounds like CBD are extracted from cannabis sativa, the flowering plant that produces widely divergent levels of THC depending on the cultivar.

The main difference between hemp and marijuana is the level of THC — hemp cannot contain more than .3 percent of THC. Long prized for its textile and rope-making fibers, hemp was banned in the 1930s during a spasm of anti-drug fervor that is perhaps best captured by the cult classic film “Reefer Madness.”

In the United States, Congress reversed the prohibition on hemp cultivation in 2018, which has fed the expanding market for CBD oil and myriad products containing it, but hemp cannot legally be fed to livestock.

“Hemp farmers are struggling to deal with tons of this unwanted biomass,” said Jonathan Miller, general counsel of the U.S. Hemp Roundtable, an industry group.

The German study provides both hope for growers and reasons for caution. Researchers discovered that the naturally occurring but limited levels of THC in most industrial hemp had no effect on the 10 cows in the experiment. But when they fed the animals flower buds and leaves — parts of the hemp plant that contain higher concentrations of the THC — researchers found that the cows ate less and that milk production dropped significantly.

Perhaps more important, at least for humans, the THC made its way into their milk, sometimes at levels that exceeded consumption limits set by food safety regulators in Europe. (The United States has no comparable standard. The Centers for Disease Control and Prevention does advise new mothers to avoid marijuana and CBD products while breastfeeding, saying the research on the effects of passing even trace amounts to an infant remains unclear.)

That said, THC became undetectable soon after the hemp was removed from the cows’ diet. Apparent signs of intoxication, including red-rimmed eyes, runny noses and what the study authors described as an “unsteady gait” and “abnormal posture” faded within two days after the cows went cold turkey.

Dr. Robert Pieper, a lead author of the study, said it was unclear whether the slump in milk output was caused by THC or perhaps by one or more of the dozens of other cannabinoids or chemicals found in hemp plants.

More research was needed, he said.

“Hemp is a very versatile and valuable crop, but we have to be careful when considering whether to feed it to food-producing animals,” said Dr. Pieper, who heads the food chain safety division at the German Federal Institute.

The findings are largely in sync with other recent studies conducted in the United States that involved hemp and livestock. Researchers at Oregon State University who fed hemp to sheep found small amounts of THC in the animal’s muscle and fat, but the chemical vanished several weeks after the hemp was removed from their diet. Serkan Ates, an associate professor at Oregon State’s College of Agricultural Sciences, said the studies he and his colleagues had done with sheep and dairy cows had convinced him that there are few downsides to introducing hemp into the diets of farm animals, especially given the soaring cost of conventional feed. “The nutritional value of hemp is really high but most of it is ending up in landfill or being composted,” he said.

In studies done at Kansas State University, THC showed up in the plasma of hemp-fed cattle, but researchers there also discovered something unexpected: The animals were notably more relaxed, according to biomarkers that indicate stress levels. As in the German study, which recorded lower heart and respiratory rates in cows that consumed high levels of THC, the animals also spent more time lying down alongside their barn mates.

Michael Kleinhenz, an assistant professor of beef production medicine at Kansas State who took part in the studies, said the findings suggested that THC-suffused hemp might have practical benefits. For one, steers that spend more time lounging around tend to put on more weight, but a blissed out cow is also a healthier one, Professor Kleinhenz said.

He cited preliminary research suggesting that reducing stress can help ameliorate the negative effects of shepherding cattle to the final chapter of their lives, when they are packed into trucks that take them to feedlots and eventual slaughter. The experience is not a pleasant one, and it is often followed by a spike in respiratory illness and other health problems.

Professor Kleinhenz said that taking the edge off that nerve-jangling journey with a bit of weed in the feed, as it were, could make for a happier cow and improve the bottom line for farmers. “Any time we make things better for the animal,” he said, “it’s a win for us.”