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 Monday 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.
It’s illegal to feed cows hemp in the United States, but 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 solely 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.