How The U.S. Dairy Sector Is Quietly Experimenting With Hemp Byproduct Feed
They came to the barn as the first light of dawn touched the silos—Jersey cows, patient and rhythmic in their chewing, each a living laboratory for a study that could ripple across agriculture.
In their troughs would go a curious new feed: spent hemp biomass, a fibrous leftover of cannabidiol (CBD) extraction. Could this discarded plant residue find new life nourishing dairy cows without harming their health—or the safety of milk?
That question lies at the heart of a pioneering study conducted by researchers at Oregon State University (OSU), led by Dr. Massimo Bionaz and his international team. Their results, published in the Journal of Dairy Science, and publicized in press releases, lab news, and agricultural outlets, suggest a cautiously hopeful “yes”—with significant caveats.
The Promise In Hemp’s Shadow
Hemp cultivation has surged over recent years, especially as farmers tap its stalks and flowers for cannabinoids like CBD. But what remains—stalks, stems, leaves—is often considered waste, or at best low-value biomass.
When that biomass is already “spent” (i.e., after cannabinoid extraction), it carries a mixed reputation: nutrient-dense, perhaps, but also containing trace cannabinoids whose fate under digestion was poorly understood.
Dr. Bionaz and his team, aware of both the risks and the opportunity, embarked on a deliberate experiment. “We know from recent research that spent hemp biomass has very promising nutritional value,” he told OSU’s newsroom.
They recruited 18 late-lactation Jersey cows, balanced for body weight and days in milk. For four weeks, half the animals received a diet in which 13 % of dry matter (DM) came from pelleted spent hemp biomass (SHB).
The other half received a control supplement: alfalfa pellet, also 13 % DM. After that, a withdrawal phase of four weeks followed, in which hemp was removed entirely. The researchers tracked a suite of parameters: feed intake, milk yield and composition, body condition, blood biomarkers, nitrogen metabolism, methane emissions, and activity levels.
Their cautious conclusion: spent hemp biomass, though less palatable, was safe when included at modest levels—and did not impair milk yield or cow health.
Shades Of Caution: Intake, Adaptation, Withdrawal
The cows did not eat as much when the hemp supplement was present. Dry matter intake (DMI) fell—likely because of hemp’s unfamiliar odor (“skunk-like,” as one researcher put it) and texture.
Nevertheless, milk yield remained stable, and during the withdrawal period even rose above that of the control group. That resulted in better efficiency—milk per unit feed consumed.
Milk composition—fat, protein, lactose—showed no alarming changes, although there was a tendency for slight fat decrease. Nitrogen use efficiency improved a little.
Methane and CO₂ emissions, expressed per cow or per milk yield, did not change significantly, though the hemp-fed group showed numerically lower greenhouse gas emissions.
In terms of animal welfare, cow activity (steps per day, lying time, restlessness) and stress indicators held steady. Blood markers of immunity, oxidative stress, liver function remained within normal ranges.
But the most delicate part of the question is: do cannabinoids enter milk or body tissues—and if so, do they disappear?
Vanishing Act: Cannabinoids And The Withdrawal Period
Because spent hemp biomass carries trace cannabinoids, especially delta-9 tetrahydrocannabinol (THC) and CBD derivatives, the possibility of residues in milk or meat has loomed as a regulatory and public health barrier.
A follow-up OSU press release, published in June 2025, reported that after a withdrawal period of two weeks, trace levels of THC became undetectable in milk and edible tissues. In fact, the researchers found that cannabinoids were absorbed in the early days of hemp feeding, but cleared within about 15 days when hemp was removed.
That is significant: “Two weeks of spent hemp biomass withdrawal … eliminates any risk of ingesting THC by consuming the milk from those cows,” Bionaz stated. Another summary described how beyond milk, THC still lingered in fat tissue for up to 30 days—but crucially, not in the milk after 12–15 days.
In short: with sufficient withdrawal, the milk supply can be cleared of concerning cannabinoids.
Global Views And Skepticism
While OSU’s study is groundbreaking, media coverage and commentary reflect both excitement and caution. Capital Press noted the potential value: CBD extraction leaves vast amounts of biomass with little economic use—turning it into feed could create efficiencies. Dairy Global framed the result as a potential substitute for forage, though highlighting that regulatory approval remains the stumbling block.
In more technical circles, Science published a 2022 piece capturing early curiosity—and wariness—about hemp in cattle feed, even quoting playful fears about cows becoming “high.” Some critics argue that long-term studies, varied breeds, different environmental conditions, and scaled-up farm settings are necessary before wide adoption.
Still, OSU’s scientists maintain a tone of humility. Their long-term goals include extending trials to other ruminants, exploring longer-term adaptation (might cows grow accustomed to hemp’s taste?), and supporting data that may persuade regulators.
Why This Matters: Farms, Climate, And Food Systems
What feels revolutionary about this experiment is not just a clever recycling trick. It strikes at several converging pressures faced by dairy and crop farming globally:
- Feed Cost And Volatility: Dairy operations often struggle with fluctuations in the price and availability of traditional forages like alfalfa and soy. A feed byproduct of hemp (which is often under-utilized) could provide a supplemental resource.
- Waste Valorization: CBD extraction generates tons of biomass that often lacks value. Converting that into feed shifts waste and resource streams toward circular agriculture.
- Environmental Gains: Improvement in nitrogen efficiency, and potential slight reductions in greenhouse emissions per unit of milk, hint at sustainability dividends.
- Regulatory And Food Safety Reassurance: Showing that milk can be cleared of psychoactive residues, with careful management, is crucial for consumer confidence.
If this approach passes further tests, the result could be a gentle revolution in how crop and livestock sectors integrate—each making use of the other’s residues and waste streams.
Cautions, Unknowns, And Next Steps
This experiment, while robust, is limited by scale: 18 cows, over a short term. It used a single breed (Jerseys), in controlled conditions. Farmers in warmer climates or with different breeds, feedstocks, disease pressures, or mastication behaviors might see different outcomes. The taste barrier and lower intake remain measurable hurdles.
Regulators will demand broader toxicology, residue studies, ecological assessments, and food chain modeling. Public perception—will consumers accept “hemp-fed” milk—is another variable.
The next phase, as the OSU project statement notes, is extension: outreach, producer adoption trials, exploring adaptation over months or years, and deeper safety profiling.
Dawn And Horizon
As churned milk crates sweep down the barn corridor, the experiment ends, but a vision remains. A feed once discarded for its cannabinoid residue now poses as a sustainable supplement—provided science, policy, and trust continue to align.
In a world where resource scarcity and climate challenge every link of the food system, experiments like this illuminate a hopeful path: innovation not in spite of nature, but with it.
If these early findings hold, spent hemp biomass may one day become more than leftover—it could be a quiet ally in nourishing animals, farmers, and a more circular agriculture.
Let us watch—and hope—that experiments in barns become practices across fields, with care, integrity, and wisdom.
