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.
Power Terms
Spent Hemp Biomass (SHB):
Spent Hemp Biomass refers to the leftover plant material after extracting CBD (cannabidiol) from hemp flowers and leaves. It is important because it repurposes agricultural waste into a resource, reducing landfill use and offering a sustainable feed option for livestock. SHB is used in animal diets as a protein and fat source. For example, after CBD is extracted using solvents like ethanol, the remaining stalks and leaves become SHB, which can replace alfalfa in lamb feed.
Cannabidiol (CBD):
Cannabidiol is a non-psychoactive compound found in hemp, valued for its potential health benefits, such as reducing anxiety or inflammation. Unlike THC, CBD does not cause a “high.” It is used in products like oils, capsules, and creams. For instance, CBD oil is popular for pain relief in humans. In the study, CBD was a primary component of SHB but did not transfer to lamb meat.
Tetrahydrocannabinol (THC):
Tetrahydrocannabinol is the psychoactive compound in cannabis responsible for the “high” sensation. While hemp contains less than 0.3% THC (legal limit), higher amounts are found in marijuana. In livestock feed, THC is regulated to prevent residues in meat. The study confirmed SHB had 0.032% THC, well below the legal threshold, and no THC was detected in lamb meat.
Crude Protein:
Crude protein measures the total protein content in feed, calculated by analyzing nitrogen levels (formula: % crude protein = % nitrogen × 6.25). It is vital for animal growth and muscle development. For example, SHB contains 20.7% crude protein, similar to alfalfa, making it a viable protein source for lambs.
Crude Fat:
Crude fat refers to the total lipid content in feed, providing energy and essential fatty acids. SHB contains 7.5% crude fat, higher than alfalfa, which supports energy needs in livestock. However, high fat content may require dietary adjustments to balance energy intake.
Neutral Detergent Fiber (NDF):
Neutral Detergent Fiber measures the indigestible plant cell wall components, such as cellulose and lignin. Lower NDF (e.g., SHB’s 27%) improves feed digestibility. For instance, SHB’s low fiber content allows lambs to absorb more nutrients compared to high-fiber forages like hay.
Mycotoxins:
Mycotoxins are toxic compounds produced by molds that grow on crops. They are harmful to animals and humans, causing illnesses like liver damage. The study confirmed SHB was free of mycotoxins, ensuring its safety as feed. An example is aflatoxin, a common mycotoxin in improperly stored grains.
Heavy Metals:
Heavy metals, such as lead and arsenic, are toxic elements that can accumulate in plants from contaminated soil. Their presence in feed is strictly regulated. The study tested SHB for heavy metals and found levels within safe limits, making it suitable for livestock consumption.
Metabolizable Energy (ME):
Metabolizable Energy represents the usable energy animals derive from feed after digestion. It is calculated using formulas like ME (Mcal/kg) = 0.0157 × D-value (digestible organic matter). SHB diets provided 3.0–3.08 Mcal/kg, ensuring lambs received adequate energy for growth.
Dry Matter Intake (DMI):
Dry Matter Intake measures the amount of feed consumed minus its water content. It helps assess feed efficiency. In the study, lambs initially ate less SHB (1,314 g/day) but adapted over time, reaching 1,827 g/day in the 10% SHB group.
Alkaline Phosphatase (ALP):
Alkaline Phosphatase is an enzyme in the liver and bones. Elevated levels can indicate metabolic stress. SHB-fed lambs showed a 30% ALP increase initially, but levels normalized, suggesting temporary adaptation without long-term harm.
Aspartate Aminotransferase (AST):
Aspartate Aminotransferase is a liver enzyme released during cell damage. Stable AST levels in SHB-fed lambs indicated no liver injury, confirming the safety of SHB over the study period.
Gamma-Glutamyl Transferase (GGT):
Gamma-Glutamyl Transferase is another liver health marker. Normal GGT levels in all groups showed SHB did not impair liver function, even at 20% inclusion.
Creatinine:
Creatinine is a waste product from muscle metabolism, filtered by kidneys. Stable creatinine levels in SHB-fed lambs indicated healthy kidney function, alleviating concerns about renal stress.
Ferric-Reducing Antioxidant Power (FRAP):
FRAP measures the antioxidant capacity of blood to neutralize free radicals. SHB-fed lambs showed a 20% FRAP increase, suggesting improved antioxidant defense, likely due to hemp’s natural phenolic compounds.
Omega-3 Fatty Acids:
Omega-3 fatty acids are essential fats with anti-inflammatory benefits. SHB increased omega-3 levels in lamb fat (4.4% vs. 3.9% in controls), enhancing the nutritional value of meat for human consumers.
Hot Carcass Weight:
Hot Carcass Weight is the weight of the lamb’s body after slaughter, excluding non-meat parts. All groups had similar weights (~25–27 kg), proving SHB did not reduce meat yield.
Shrink Loss:
Shrink Loss measures weight reduction in carcasses during refrigeration. SHB-fed lambs had higher shrink loss (8.8% vs. 5.6%), likely due to lower fat content, which reduces moisture retention.
Shear Force:
Shear Force quantifies meat tenderness by measuring the force (in Newtons) required to cut through muscle. SHB-fed lamb meat had higher shear force (34 N vs. 24.7 N), indicating slightly tougher texture, possibly due to leaner muscle.
Carbon-Neutral Cycle:
A Carbon-Neutral Cycle balances CO2 emissions with absorption. Hemp absorbs 15 tonnes of CO2 per hectare, making SHB-fed livestock part of a sustainable system that mitigates climate impact.
Circular Economy:
A Circular Economy reuses waste as resources. Using SHB as feed instead of discarding it exemplifies this model, turning agricultural byproducts into valuable inputs for farming.
Dry Matter Digestibility:
Dry Matter Digestibility is the proportion of feed absorbed by the animal. SHB’s digestibility was 7–10% higher than alfalfa, meaning lambs extracted more nutrients from the same amount of feed.
CO2 Absorption:
CO2 Absorption refers to plants capturing carbon dioxide from the atmosphere. Hemp’s rapid growth and high absorption rate (15 tonnes/ha) make it an eco-friendly crop that supports climate goals.
Feed Inclusion Rate:
Feed Inclusion Rate is the percentage of a specific ingredient (like SHB) in an animal’s diet. The study tested 10% and 20% rates, finding 10% optimal for palatability and digestibility.
Consumer Acceptance Studies:
Consumer Acceptance Studies assess public willingness to buy products like “hemp-fed” meat. While not part of this research, such studies are crucial for market adoption, ensuring transparency about safety and benefits.
Reference:
Parker, N. B., Bionaz, M., Ford, H. R., Irawan, A., Trevisi, E., & Ates, S. (2022). Assessment of spent hemp biomass as a potential ingredient in ruminant diet: nutritional quality and effect on performance, meat and carcass quality, and hematological parameters in finishing lambs. Journal of Animal Science, 100(10), skac263.
