Spent Hemp Biomass Could Be a Game-Changer for Sustainable Lamb Feed

Add Cultivation AG as a preferred Google News source to see more of our trusted agriculture, farming, and crop coverage.

The global hemp industry, valued at 3.7 billion in 2018, is projected to grow to 26.6 billion by 2025, driven largely by demand for cannabidiol (CBD)—a non-psychoactive compound extracted from hemp flowers for its potential health benefits. However, this rapid expansion generates significant agricultural waste, including spent hemp biomass (SHB)—the fibrous residue left after extracting CBD from hemp flowers and leaves.

Historically discarded or underutilized, SHB is now gaining attention as a potential feed ingredient for livestock. A landmark 2022 study published in the Journal of Animal Science investigated SHB’s nutritional value, safety, and effects on lamb health and meat quality.

Understanding Spent Hemp Biomass (SHB)

Spent hemp biomass (SHB) refers to the leftover plant material after CBD extraction. Hemp (Cannabis sativa) is a versatile crop cultivated for fibers, seeds, and CBD oil. The extraction process—often using solvents like ethanol or pressurized CO2—removes cannabinoids like CBD and tetrahydrocannabinol (THC), the psychoactive compound in cannabis.

However, SHB retains substantial nutritional value. Researchers analyzed SHB’s composition and found it comparable to alfalfa, a staple in livestock diets. SHB contains 20.7% crude protein (a measure of total protein content), 7.5% crude fat (total lipid content), and essential minerals like calcium, phosphorus, and zinc. Its low neutral detergent fiber (NDF: 27%)—a metric for plant cell wall content—makes it easier to digest than traditional forages like hay.

Importantly, SHB tested negative for mycotoxins (toxic fungal byproducts), heavy metals (e.g., lead, arsenic), and solvent residues, addressing initial safety concerns. However, SHB contains trace cannabinoids, including 0.032% THC (below the 0.3% legal limit) and 3% total cannabinoids, primarily non-psychoactive CBDA (62.5%) (carboxylic acid form of CBD) and CBD (9.4%).

Despite its potential, SHB remains unapproved by the U.S. Food and Drug Administration (FDA) for livestock feed due to unresolved questions about long-term animal health impacts.

Study Design and Methodology

To evaluate SHB’s viability, researchers at Oregon State University conducted an 8-week feeding trial involving 35 male Polypay lambs, a breed known for rapid growth and high meat yield. Each lamb was approximately 6 months old and weighed 44.7 kg at the study’s start. The lambs were divided into five groups, each fed a different diet:

• Control (CON): 0% SHB.
• LH1: 10% SHB for the first 4 weeks, then 0% SHB for the remaining 4 weeks.
• LH2: 10% SHB for all 8 weeks.
• HH1: 20% SHB for the first 4 weeks, then 0% SHB for the remaining 4 weeks.
• HH2: 20% SHB for all 8 weeks.

Diets were carefully balanced to ensure equal energy (3.0–3.08 Mcal/kg metabolizable energy—a measure of usable energy in feed) and protein (12% crude protein) across all groups. SHB replaced alfalfa in the experimental diets—for instance, the 20% SHB diet eliminated alfalfa entirely.

Researchers tracked daily dry matter intake (DMI) (total feed consumed minus moisture), weight gain, blood parameters (e.g., glucose, cholesterol, liver enzymes), and post-slaughter meat quality (tenderness, fat content, cannabinoid residues).

Feed Intake and Digestibility

During the first 4 weeks, lambs fed 20% SHB (groups HH1 and HH2) consumed 12–15% less feed (1,314 g/day) compared to the control group (1,496 g/day). This initial reluctance was likely due to SHB’s strong odor or bitter taste, a common issue with novel feed ingredients.

However, by weeks 5–8, lambs in the 10% SHB group (LH2) showed a 20% increase in feed intake (1,827 g/day vs. 1,521 g/day for controls), suggesting they adapted to the new diet.

Digestibility—the proportion of feed absorbed by the body—tests revealed SHB-fed lambs had 7–10% higher dry matter digestibility, attributed to SHB’s lower fiber content compared to alfalfa. These results highlight the importance of gradually introducing SHB to avoid initial feed refusal.

Metabolic and Health Impacts

Short-term effects of SHB included reduced blood glucose (15% lower in 20% SHB groups) and cholesterol (18% decrease), likely due to altered fat metabolism. Glucose is a primary energy source for cells, while cholesterol is essential for cell membranes and hormone production.

Vitamin E levels—a key antioxidant protecting cells from damage—also dipped by 25%, possibly linked to reduced fat absorption. Notably, liver enzymes like alkaline phosphatase (ALP)—an indicator of bone or liver activity—rose by 30%, suggesting mild stress on metabolism.

However, long-term data showed no liver or kidney damage, with aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT)—markers of liver health—and creatinine (a kidney function indicator) remaining within normal ranges.

Antioxidant capacity improved in lambs fed SHB continuously, as evidenced by a 20% increase in FRAP (ferric-reducing antioxidant power) levels—a test measuring the ability of blood to neutralize free radicals. These findings suggest SHB causes temporary metabolic adjustments but poses no serious health risks over time.

Carcass and Meat Quality

Post-slaughter analysis revealed no differences in hot carcass weight (~25–27 kg)—the weight of the carcass immediately after slaughter—between groups. However, SHB-fed lambs had higher shrink loss (8.8% vs. 5.6% in controls), a measure of weight loss during refrigerated storage, likely due to reduced subcutaneous fat.

Meat from SHB-fed lambs lost 18–20% moisture during cooking (vs. 14% in controls), possibly due to leaner muscle composition. Shear force—a tenderness metric measured in Newtons (N)—varied slightly, with meat from the HH1 group being 38% tougher (34 N shear force vs. 24.7 N in controls).

On a positive note, SHB increased omega-3 fatty acids (specifically 18:3ω3) in adipose tissue (4.4% vs. 3.9% in controls), enhancing the nutritional profile of the meat. Omega-3s are essential fats linked to heart health and anti-inflammatory benefits in humans.

Despite containing 0.032% THC, no cannabinoids were detected in lamb muscle or fat. Blood tests also showed undetectable THC levels, confirming that SHB does not transfer cannabinoids to animal products. This finding addresses a major regulatory concern and strengthens the case for SHB’s approval as livestock feed.

Practical Implications for Farmers and Broader Agricultural Impact

For farmers, SHB offers a dual advantage: reducing feed costs and supporting sustainability. Replacing alfalfa with SHB could lower expenses by 15–20%, based on current market prices. To maximize benefits, farmers should start with a 10% SHB inclusion rate, gradually increasing it as animals adapt.

Mixing SHB with palatable ingredients like molasses or grains can mask its bitterness. Additionally, SHB’s high fat content (7.5%) may require adjustments to energy ratios in feed formulations to prevent overconsumption. Beyond cost savings, using SHB addresses two critical challenges: agricultural waste reduction and carbon footprint mitigation.

Each hectare of hemp cultivation produces 200–500 kg of SHB, which would otherwise end up in landfills. Hemp’s rapid growth and high CO2 absorption (15 tonnes per hectare)—a process where plants capture carbon dioxide from the atmosphere—make SHB-fed livestock part of a carbon-neutral cycle. Policymakers must now reconsider outdated regulations to unlock SHB’s potential, fostering a circular economy in agriculture, where waste is repurposed into resources.

While promising, the study had limitations. The small sample size (7 lambs per group) may limit statistical power, and the 8-week trial period leaves long-term effects unanswered. Future research should explore SHB in larger cohorts over 6–12 months and extend trials to other livestock, such as cattle and poultry. Consumer acceptance studies—assessing public willingness to buy “hemp-fed” meat—are also needed to gauge market readiness.

Conclusion

The 2022 study provides robust evidence that spent hemp biomass is a safe, nutritious feed alternative for lambs. While high SHB inclusion rates (20%) initially reduce feed intake, lambs adapt without adverse health effects. Meat quality remains largely unchanged, with added benefits from omega-3 fatty acids.

For farmers, SHB presents an opportunity to cut costs and adopt eco-friendly practices. Regulatory bodies must now act on this data, reclassifying SHB to enable its use in livestock diets. As the hemp industry grows, transforming “waste” into valuable feed could revolutionize agriculture, making it more sustainable and efficient for future generations.