The National Post reports in its Tuesday, Nov. 15, edition that cows appear to get stoned after eating hemp feed and then produce milk that could make people drowsy, a new study suggests. A Daily Telegraph dispatch to the Post reports that there has been little research on whether cows experience unwelcome or welcome physiological effects and whether any of the psychoactive properties of cannabis could be passed on to humans through the food chain. Germany decided to find out. Researchers at the German federal institute of risk assessment gave cannabinoid-rich industrial hemp silage to 10 dairy cows. They discovered animals showed significant behavioural changes, including increased yawning, salivation, tongue play and unsteady movements. The cows appeared drowsy and often stood for unnaturally long periods in abnormal postures. Researchers found the milk had high levels of THC. Levels in the milk were so high that humans who drank it could suffer drowsiness, impaired working memory and mood alterations, the researchers said. "We observed significant changes in respiratory and heart rate as well as a reduction of feed intake and milk yield," a spokesman said.