Spent Hemp Biomass As Stock Feed

Recent research out of Oregon State University has provided promising results concerning feeding cows spent hemp biomass.

After cannabinoids are extracted from hemp, the spent biomass is still useful as stock feed given its nutritional hemp profile. This waste has high protein content and contains desirable fatty acids, and could replace other protein-source ingredients such as soybean alfalfa as spent hemp biomass is largely comparable to alfalfa in terms of amino acid composition. The waste also contains phytochemicals with antioxidant, anti-inflammatory, and antimicrobial properties.

But in many jurisdictions use of spent hemp biomass in such a way is still banned; primarily due to concerns about the potential presence of delta-9 tetrahydrocannabinol (Δ9-THC) winding up in products such as meat and milk. Only hempseed meal is legalized as a feed ingredient, and only in a few countries.

Researchers from Oregon State University have delved into the accumulation and clearance of cannabinoids in milk and tissues of dairy cows fed spent hemp biomass. Their project involved 18 Jersey cows, from which nine were fed a diet containing 13% spent hemp biomass, and the other nine received a control diet containing 13% alfalfa pellet instead of the spent hemp biomass. The cows then went through a four-week withdrawal period, with all receiving the control diet.

While initially detecting cannabinoids in the tissues and milk of dairy cows soon after withdrawal, there was less than 1% transfer of cannabinoids in the milk. However, a high accumulation of  THC was detected in adipose tissue (fat).

But twelve days after withdrawing spent hemp biomass as feed, Δ9-THC in milk was undetectable. At this point though, it was still detectable in adipose tissue, and didn’t clear until 30 days after withdrawal.

The researchers also noted CBD and CBD-acid (CBDA) were detectable in the plasma of cows after calving (i.e., 90 days after withdrawal).

“This study is one step forward in providing the data needed for FDA approval of spent hemp biomass as a feed supplement for livestock,” said Massimo Bionaz, lead author of the study.

The research was published in May 2025 in the Journal of Agricultural and Food Chemistry.

Currently, spent hemp biomass has little to no economic value for hemp producers — allowing it to be fed to cows could be a game-changer and a win-win for all.