Transfer of cannabinoids into the milk of dairy cows fed with industrial hemp could lead to Δ⁹-THC exposure that exceeds acute reference dose

The industrial hemp sector is growing and, in recent years, has launched many novel hemp-derived products, including animal feed. It is, however, unclear to what extent individual cannabinoids from industrial hemp transfer from the feed into products of animal origin and whether they pose a risk for the consumer. Here we present the results of a feeding experiment with industrial hemp silage in dairy cows. Hemp feeding included changes in feed intake, milk yield, respiratory and heart rates, and behaviour. We combined liquid chromatography-tandem mass spectrometry-based analyses and toxicokinetic computer modelling to estimate the transfer of several cannabinoids (Δ⁹-tetrahydrocannabinol (Δ⁹-THC), Δ⁸-THC, Δ⁹-tetrahydrocannabinolic acid, Δ⁹-tetrahydrocannabivarin, 11-OH-Δ⁹-THC, 11-nor-9-carboxy-Δ⁹-THC, cannabidiol, cannabinol and cannabidivarin) from animal feed to milk. For Δ⁹-THC, which has a feed-to-milk transfer rate of 0.20% ± 0.03%, the acute reference dose for humans was exceeded in several consumer groups in exposure scenarios for milk and dairy product consumption when using industrial hemp to feed dairy cows.