UK study points to potential food-safety risks in hemp plant tops that are fed to cattle

A new peer-reviewed cattle-feeding study is raising red flags over the potential use of industrial hemp plant tops as sustainable input for livestock feed, particularly in the beef sector.

The research, published in Scientific Reports, a Nature Portfolio journal based in London, examined what happens when cattle are fed industrial hemp inflorescence — the flower- and leaf-rich portion of the plant that contains the highest concentrations of cannabinoids. The findings point to long-lasting cannabinoid residues in meat and fat, a result that could complicate regulatory approvals, liability exposure and market acceptance for some hemp-derived feed streams.

For hemp processors, feed suppliers and beef producers exploring circular-economy use cases, the study suggests that not all hemp “waste” is commercially interchangeable.

Differing derivatives

Hemp seed, seed meal and stalks contain negligible cannabinoid levels and have not shown comparable residue concerns in prior research. Those materials are structurally and chemically distinct from plant tops, and have been treated as lower-risk inputs in regulatory discussions.

From a business perspective, long withdrawal intervals significantly undermine the economic logic of using cannabinoid-rich hemp flowers as cattle feed. However, the findings should not be read as an indictment of hemp feed more broadly. In practical terms, the study reinforces an emerging segmentation within hemp feed markets: seed- and fiber-based materials may remain viable, while inflorescence and post-extraction biomass face much higher regulatory and reputational hurdles.

What was tested

In the Scientific Reports study, researchers fed 20 Holstein steers a daily ration of industrial hemp flowers and leaves for 14 days, providing approximately 4.2 milligrams per kilogram of cannabidiolic acid (CBDA). After hemp feeding stopped, tissues were sampled over several days to track how cannabinoids dissipated from liver, kidney, muscle and fat.

The study found that multiple cannabinoids persisted in cattle tissues well after hemp feeding ended. Low levels of delta-9 THC appeared in liver, kidney and fat tissue, while CBD and other cannabinoids were present across all sampled tissues.

Most notably for food-safety and compliance discussions, cannabinoid depletion from fat was slow. Using CBD as the most conservative marker, the authors estimated that cattle could require a withdrawal interval of up to five months before residues fall to negligible levels.

A worst-case consumer-exposure model suggested that infants consuming beef fat from such animals could exceed conservative international acute reference doses for THC — a hypothetical scenario, but one that regulators typically take seriously.

Industry implications

Near-term outcomes the industry may need to contend with include:

• Increased regulatory scrutiny of hemp inflorescence and post-extraction biomass in livestock feed.
• Pressure to segregate feed-grade hemp inputs by plant part and cannabinoid content
• Greater liability and insurance concerns for beef producers using cannabinoid-rich hemp materials.
• Expanded demand for follow-on studies, particularly at lower doses and in dairy systems.

The research team included scientists from Kansas State University, which has led the U.S. research program on hemp in livestock and contributors from institutions with regulatory- and veterinary-science expertise — among them investigators affiliated with U.S. Food and Drug Administration’s Center for Veterinary Medicine and other academic veterinary research units.