Cannabinoid Distribution and Clearance in Feeding Spent Hemp Biomass to Dairy Cows and the Potential Exposure to Δ9-THC by Consuming Milk

Spent hemp biomass (SHB) is the byproduct of the cannabinoid extraction from hemp. Despite having an excellent nutritional profile, it cannot legally be used as a feed ingredient in livestock mainly due to the presence of Δ⁹-tetrahydrocannabinol (Δ⁹-THC), which could accumulate in animal products, posing a risk for consumers. This study investigated the accumulation and clearance of cannabinoids in milk and tissues of dairy cows fed SHB and the risk for people consuming the milk from those cows. Using UHPLC-MS/MS, we detected cannabinoids in the tissues and milk of dairy cows fed SHB, with less than 1% transfer of cannabinoids in the milk. A high accumulation of Δ⁹-THC was detected in the adipose tissue. Twelve days after SHB withdrawal, Δ⁹-THC in milk was undetectable, but it remained detectable in the adipose tissue until 30 days after SHB withdrawal. CBD and CBD-acid (CBDA) were detectable in the plasma of cows after calving (i.e., 90 days after SHB withdrawal). When consuming milk from cows fed SHB, the total THC intake exceeded the acute reference dose of 1 μg/kg BW. However, 2 weeks of SHB withdrawal from the diet of the cows eliminates any risk of ingesting Δ⁹-THC by consuming the milk from those cows.