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

Authors: Smith, David; Serum, Eric; WINDERS, TOMMY - North Dakota State University; Neville, Bryan; Herges, Grant; DAHLEN, CARL - North Dakota State University; SWANSON, KENDALL - North Dakota State University

Submitted to: Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2023
Publication Date: 3/10/2023
Citation: Smith, D.J., Serum, E.M., Winders, T.M., Neville, B.W., Herges, G.R., Dahlen, C.R., Swanson, K.C. 2023. Excretion and residue depletion of cannabinoids in beef cattle fed hempseed cake for 111 days. Food Additives & Contaminants. 40(4):552-565. https://doi.org/10.1080/19440049.2023.2187645.
DOI: https://doi.org/10.1080/19440049.2023.2187645

Interpretive Summary: Hempseed cake is a highly nutritious byproduct of oil extraction from industrial hempseed. Although hempseed oil is commonly used in food, health care, and cosmetic products, hempseed cake cannot be used in food animal rations because the magnitude of cannabinoid (CBD, THC) residues remaining in edible animal tissues has not been characterized. In this study, hempseed cake was incorporated into a balanced cattle ration and fed to a group of heifers for approximately 16 weeks. Cannabinoid residues were sporadically detected in urine and plasma during the feeding period. Low levels (10 parts per billion) of CBD/THC were measured in adipose tissue of cattle harvested with no withdrawal period. CBD/THC were below detectable levels in liver, kidney, and muscle of cattle fed hempseed cake. Exposure estimates indicated that it would be very difficult for a human to consume enough fat from cattle fed hempseed cake to exceed conservative regulatory thresholds for dietary THC.

Technical Abstract: 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 across the feeding period with total cannabidiol and tetrahydrocannabinol (CBD/THC) concentration of 1.3 ± 0.8 mg/kg. 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). 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) 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) 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 ARfD (1 µg/kg body weight).