Excretion and residue depletion of cannabinoids in beef cattle fed hempseed cake for 111 days.

Thirty-two crossbred heifers were fed either a control diet or 20% (dry matter basis) hempseed cake in a complete ration for 111 days; of the cattle fed hempseed cake, four each were harvested with 0, 1, 4, and 8-day withdrawal periods. Urine and plasma were collected during the feeding and withdrawal periods and liver, kidney, skeletal muscle, and adipose tissue were collected at harvest. Total cannabinoid (n = 10) concentration of hempseed cake averaged 11.3 ± 11.7 mg kg-1 across the feeding period with total cannabidiol and tetrahydrocannabinol (CBD/THC) concentrations of 1.3 ± 0.8 mg kg-1. Neutral cannabinoids (cannabinol [CBN], CBD/THC, and cannabidivarin [CBDV]) were not detected in plasma or urine, but CBD/THC was measured in adipose tissue at all withdrawal periods (6.3 ± 2.1 to 10.1 ± 2.5 ng g-1). In contrast, cannabinoid acids (cannabinolic acid [CBNA], cannabidiolic acid [CBDA]/tetrahydrocannabinolic acid [THCA], cannabichromenic acid [CBCA], and cannabidivarinic acid [CBDVA]) were sporadically detected (<15 ng mL-1) in plasma and urine of cattle fed hempseed cake. Cannabinoid acids were depleted from liver by withdrawal day 4, but could still be measured (<1 ng g-1) in kidney of some animals harvested on withdrawal day 8. Assessment of human exposures to CBD/THC residues through the consumption of beef fat from animals fed hempseed cake suggests that the probability of consuming the equivalent of an acute reference dose (ARfD) is remote, even with the use of a conservative reference dose ARfD (1 µg kg-1 body weight).