Study Finds Hemp-Fed Cows Had Traces of THC in Their Milk

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.