Oregon’s hemp industry generates a large volume of spent hemp biomass — the leftover plant material after cannabidiol is extracted. The material has a strong nutrient profile and could serve as a cost-competitive alternative to other forages and protein sources in cattle diets.
The research provides practical guidance that can help shape future standards, inform processor decisions and support Oregon’s leadership in hemp, livestock and agricultural innovation.
But one barrier has slowed progress: uncertainty about whether cannabinoids, including THC, could carry into milk or meat and pose a risk to consumers. Federal regulators and feed control officials have raised concerns that cannabinoids may accumulate in animal tissues or products.
For dairy, that concern is especially urgent because compounds can transfer into milk. For beef, the primary question is whether cannabinoids could remain in edible tissues at levels that would matter for consumers.
Oregon State University researchers in the College of Agricultural Sciences, Oregon Agricultural Experiment Station and the OSU Extension Service are helping fill that evidence gap with controlled feeding studies in dairy cows and beef steers.
The studies provide practical, science-based guidance for regulators, processors and livestock producers who want to turn a byproduct into a useful resource while protecting the food supply.
To evaluate animal health, product residues and the time needed for cannabinoids to clear after hemp biomass is removed from the diet, OSU researchers designed feeding trials in both dairy and beef systems.
In the dairy study, published in the Journal of Agricultural and Food Chemistry, 18 Jersey cows were fed a diet containing spent hemp biomass for 28 days, followed by a withdrawal period in which all cows returned to a control diet.
Researchers collected milk repeatedly during and after the feeding period and sampled tissues including liver, muscle and adipose tissue. Using validated, highly sensitive analytical methods, they measured cannabinoids in milk and tissues and assessed what those levels could mean for people consuming the milk.
In the beef study, published in the journal animal, 24 Angus steers were fed a diet containing 15% spent hemp biomass for eight weeks, followed by a one-month withdrawal period. Researchers tracked weight gain, feed intake and indicators of health and metabolism. They also took liver, muscle and adipose tissue biopsies at key time points to determine how cannabinoids moved through the body and how quickly they declined after withdrawal.
The dairy trial showed that cannabinoids can transfer into milk while cows are actively consuming spent hemp biomass, but that transfer is low. Less than 1% of cannabinoids ingested were measured in milk. Even so, THC was detected in milk during the feeding period, and consumer exposure estimates indicated that in a worst-case scenario, total THC intake from milk could exceed a conservative acute reference dose.
The study also identified a key operational takeaway: a withdrawal window makes a difference. THC in milk was undetectable 12 days after spent hemp biomass was removed from the diet. Researchers concluded that a two-week withdrawal period would eliminate risk of ingesting THC through milk consumption.
Tissue results reinforced why withdrawal guidance matters. THC accumulated most strongly in adipose tissue, where it remained detectable longer than in milk. That finding helps explain why clearance timelines vary by tissue and supports the need for evidence-based withdrawal recommendations.
The beef trial offered additional reassurance for the meat supply. Steers fed spent hemp biomass showed no adverse behavior effects, and overall weight gain was not different from steers fed a comparable control ration. Cannabinoids accumulated primarily in fat tissue, with very low THC detected in muscle. After 33 days of withdrawal, cannabinoids were undetectable in all tissues except cannabidiol in adipose tissue, which persisted at low levels.
For consumer protection, researchers estimated exposure to total THC from beef consumption and found it remained below the same acute reference dose threshold for all population groups, including children and high-risk consumers.
The results suggest that, under the conditions tested, spent hemp biomass can be used in stocker steer diets with minimal risk of THC exposure to consumers, especially when paired with an appropriate withdrawal period.
The research was led by faculty in the Oregon State University College of Agricultural Sciences and included faculty in the OSU Extension Service and colleagues in Italy and Indonesia.
For livestock producers and the feed industry, the findings point to clear management practices, including withdrawal periods, that reduce risk while opening the door to a more circular agricultural economy.
By testing both dairy and beef systems, OSU’s research also helps clarify that “safe use” is not a one-size-fits-all question. Milk and meat have different risk profiles, and cannabinoids behave differently in milk versus fat tissue.
The result is practical guidance that can help shape future standards, inform processor decisions and support Oregon’s leadership in hemp, livestock and agricultural innovation.
The dairy cow study was funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture through a Critical Agriculture Research and Extension grant (grant No. 2021-68008-34099).
The beef steer study was supported in part by USDA National Institute of Food and Agriculture through a Critical Agriculture Research and Extension grant (project No. ORE01002; grant No. 2021-68008-34099), the USDA Agricultural Research Service through a Non-Assistance Cooperative Agreement (project No. 2072-2100-054-00-D), and the Oregon Beef Council.