OSU Study Measures Cannabinoid Levels in Cows Fed Spent Hemp Biomass

In a recently published study, researchers with Oregon State University (OSU) tested the accumulation of cannabinoids in cows when given hemp in their feed, finding that the cannabinoids became undetectable over time. Noting that the use of spent hemp biomass (SHB) in livestock feed is currently illegal due to the safety risk posed to consumers by the presence and potential accumulation of THC, the researchers tested the accumulation of cannabinoids in the milk and tissue of cows and evaluated the risk it poses to consumers. The study, “Cannabinoid Distribution and Clearance in Feeding Spent Hemp Biomass to Dairy Cows and the Potential Exposure to Δ9-THC by Consuming Milk,” was published in May 2025 in the Journal of Agricultural and Food Chemistry.

Though industrial hemp has been legal to grow since 2018, the Food and Drug Administration (FDA) does not currently allow its addition in livestock feed, explained a June 26, 2025, news release from OSU. The news release also explained that more than 60% of hemp grown in the US is for cannabidiol (CBD) extraction, a process that results in a significant amount of the spent hemp biomass. “This study is one step forward in providing the data needed for FDA approval of spent hemp biomass as a feed supplement for livestock,” stated Massimo Bionaz, lead author of the study and an associate professor in the Department of Animal and Rangeland Sciences at OSU.

The study involved 18 Jersey cows, and for the first 28 days, nine of the cows were fed a diet containing 13% SHB and the other nine were fed a control diet with 13% alfalfa pellets. A four-week withdrawal period followed, in which all 18 cows were fed the control diet.

The researchers used ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) to measure the cannabinoid content in the milk of the cows fed the SHB, finding less than 1% of cannabinoid transfer. Additionally, a high amount of THC was detected in the fat tissue.

Other results stated in the abstract include:

• After 12 days of withdrawal, THC was not detected in milk, but it was detectable in fat tissue until 30 days after withdrawal
• CBD and cannabidiolic acid (CBDA) were detectable in the plasma of cows 90 days after withdrawal

The total intake of THC from milk from the cows fed the hemp diet surpassed the acute reference dose of 1 μg/kg BW, though this changed over time. “Two weeks of spent hemp biomass withdrawal from diet of the cows eliminates any risk of ingesting THC by consuming the milk from those cows,” explained Bionaz.

In an earlier study, published in Food Additives and Contaminants, the US Department of Agriculture (USDA) and North Dakota State University (NDSU) found that that cows fed hempseed cake will retain low concentrations of THC and CBD in their meat, particularly in the muscle, kidney, liver, and fat tissues. The hempseed cakes were described as high in crude protein and fiber, a viable alternative food source for cattle, and offered a potential market for hemp producers.

References

1. Irawan, A.; Nosal, DG.; Muchiri, RN.; van Breemen, RB.; Ates, S.; Cruickshank, J.; Ranches, J.; Estill, CT.; Thibodeau, A.; Bionaz, M. Cannabinoid Distribution and Clearance in Feeding Spent Hemp Biomass to Dairy Cows and the Potential Exposure to Δ9-THC by Consuming Milk, Journal of Agricultural and Food Chemistry 2025 73(22), 13934-13948. DOI: 10.1021/acs.jafc.5c02827
2. Nelson, S. THC undetectable after withdrawal period in cows fed hemp byproduct https://news.oregonstate.edu/news/thc-undetectable-after-withdrawal-period-cows-fed-hemp-byproduct-0 (accessed Aug 19, 2025).
3. Colli, M. USDA Finds Cows Fed Hemp Cake Can Retain Safe Levels of THC and CBD https://www.cannabissciencetech.com/view/usda-finds-cows-fed-hemp-cake-can-retain-safe-levels-of-thc-and-cbd (accessed Aug 19, 2025).