AAVS_14_8_1718-1730

Introduction

Recent research has shed light on the pharmacological potential of hemp (Cannabis sativa L.), which is attributed to its diverse composition, including a variety of phytocannabinoids, terpenes, phenolics, flavonoids, and alkaloids (Andre et al., 2016; Radwan et al., 2021). The non-psychotropic compound cannabidiol (CBD) and the psychotropic compound Δ9-tetrahydrocannabinol (THC) are currently the focus of significant research in both human and veterinary medicine (Lima et al., 2022), including growing interest in livestock species (Fallahi et al., 2022; Irawan et al., 2025).

The gut microbiota, whose composition and function are increasingly linked to cannabinoid signalling (Cani et al., 2016; Silvestri and Di-Marzo, 2023), plays established roles in metabolic regulation, immune function, and intestinal barrier integrity (Khan et al., 2025; Lynch and Pedersen, 2016). The endocannabinoid system (ECS), consisting of endogenous cannabinoids, their receptors (CB1R and CB2R), and metabolic enzymes, is particularly relevant to gastrointestinal physiology (Maccarrone et al., 2023). CB1R in the enteric nervous system and intestinal epithelium is involved in motility and secretion (Izzo and Sharkey, 2010), while CB2R in gut-associated lymphoid tissue (GALT) modulates mucosal immune responses (Turcotte et al., 2016). Both receptors have been characterized in the bovine gastrointestinal tract (Kent-Dennis and Klotz, 2024; Osiak-Wicha et al., 2024; Zachut et al., 2025) and chicken ileum (Ghazi Sahm et al., 2026). The bidirectional interaction between the ECS and the gut microbiota, termed the endocannabinoidome–microbiome axis, may influence microbiota composition, intestinal barrier integrity, and microbial metabolite production (Cani et al., 2016; Silvestri and Di Marzo, 2023), though how dietary hemp compounds interact with this system in farm animals remains largely unexplored.

As the commercial use of hemp-derived supplements continues to increase in livestock (Fallahi et al., 2022; Irawan et al., 2025) animals, the mechanistic effects of cannabinoids on host physiology and gut microbiota remain incompletely understood. Existing studies suggest that cannabinoids may influence intestinal microbial composition, barrier integrity, and metabolic activity; however, current data are still somewhat limited and heterogeneous. This review aims to evaluate the existing literature on the effects of dietary hemp and hemp-derived products on the intestinal microbiota of ruminants and broilers, with emphasis on study designs, key findings, methodological limitations, and future research priorities.

Literature search strategy

A literature search was performed in Google Scholar, PubMed, Scopus, and Web of Science for records published from January 2008 to April 2026. The last search was performed on 15 April 2026. The search terms were adapted to the syntax of each database and combined into three groups of terms. The terms related to hemp and cannabinoids were Cannabis sativa, hemp, industrial hemp, hempseed, hemp seed cake, hemp seed meal, hemp oil, cannabinoids, CBD, and phytocannabinoids. The microbiota and fermentation-related terms included microbiota, microbiome, gut bacteria, rumen, cecum (caecum), fermentation, short-chain fatty acids, SCFA, and methane. Species included poultry, broiler, chickens, ruminants, cattle, cows, goats, and sheep. Peer-reviewed conference proceedings and meeting abstracts, as grey literature, were also eligible and identified using Google Scholar and by hand-searching the reference lists of retrieved articles.

Records were eligible if they were original peer-reviewed studies reporting a direct gut microbiota or microbial outcome following dietary hemp-derived or cannabinoid exposure in ruminants or poultry. Studies in non-livestock species, those using non-dietary administration, and those reporting only performance, morphology, or immune endpoints without microbiota measurements were used only for supporting context. From the 412 records identified, 89 duplicates were removed and 323 were screened by title and abstract (287 excluded); of 36 full texts assessed, 20 were excluded at this stage (no direct microbiota or microbial outcome reported, reporting of performance, product quality, or agronomic endpoints only, or non-dietary administration), leaving 16 studies for the final narrative synthesis (9 ruminant or in vitro rumen and 7 poultry or in vitro gut studies).

Cannabinoids

Δ9-Tetrahydrocannabinol (THC) is acknowledged as the principal psychoactive compound found in Cannabis sativa. It plays a significant role in the regulation of gastrointestinal motility, secretion, and intestinal barrier function. This occurs through its interactions with both the central and enteric nervous systems, primarily via binding to CB1 receptors with a high affinity (Irawan et al., 2025). Although THC activates CB1R in the central and enteric nervous systems at pharmacologically relevant concentrations, industrial hemp varieties contain THC below 0.3% by dry weight (Farinon et al., 2020). Given this low concentration, the levels of THC that can be achieved in the gastrointestinal system from typical dietary intake in farm animals may fall short of the threshold necessary for significant activation of CB1 receptors. Cannabidiol (CBD) is a non-psychotropic phytocannabinoid that, despite exhibiting low affinity for CB1 and CB2 receptors (Table 1), exhibits a broad spectrum of biological effects through diverse molecular targets, including Transient Receptor Potential Vanilloid Type 1 (TRPV1), G Protein-Coupled Receptor 55 (GPR55), 5-Hydroxytryptamine (Serotonin) Receptor 1A (5-HT1A) receptors, and Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) (Pertwee, 2008). Recent studies have shown that CBD influences intestinal PPARα expression, with PPAR-related responses correlating with tight-junction genes in broilers (Szkopek et al., 2024). Furthermore, the bovine small intestine has been identified as containing CB1R, CB2R, and TRPV1, with notable increased

Table 1: Receptor targets and physiological effects of selected phytocannabinoids from Cannabis sativa L.

Compound	Receptor targets	Main biological effects	References
THC	CB1R (high affinity), CB2R (moderate)	Analgesia, appetite stimulation, antiemetic effects, regulation of gastrointestinal motility	Pertwee (2008)
CBD	GPR55, TRPV1, 5-HT1A, PPARγ	Anti-inflammatory, antioxidant, anxiolytic, modulation of intestinal barrier function	Boehm et al. (2023); Brown et al. (2024); Ibeas et al. (2015)
CBG	CB1R/CB2R (weak), α2-adrenergic receptors	Antimicrobial, neuroprotective, anti-inflammatory	Li et al. (2024)
CBC	TRP, PPARγ	Anti-inflammatory, analgesic, antimicrobial	Sepulveda et al. (2024)
CBN	CB1R (weak), CB2R (moderate), TRP	Sedative effects, antibacterial activity	Farha et al. (2020); Morales et al. (2017)
THCV	CB1R antagonist/agonist (dose-dependent), CB2 partial agonist, TRP	Appetite suppression, potential anticonvulsant activity, anti-inflammatory	Walsh et al. (2021)
CBDA	COX-2 inhibition, PPARγ, TRP, 5-HT1A	Anti-inflammatory, anti-emetic	Formato et al. (2020)
Β-Caryophyllene	CB2 agonist (selective)	Anti-inflammatory, antimicrobial activity against rumen methanogens (in vitro)	Tabiś et al. (2024); Russo (2011)

Δ9-tetrahydrocannabinol: THC, Cannabidiol: CBD, Cannabigerol: CBG, Cannabichromene: CBC, Cannabinol: CBN, Tetrahydrocannabivarin: THCV, Cannabidiolic acid: CBDA.

expression of TRPV1 in the jejunum (Osiak-Wicha et al., 2024). However, the extent to which dietary hemp modulates microbiota through endocannabinoid system-related signaling in farm animals remains to be clarified. Additionally, minor phytocannabinoids such as cannabichromene (CBC), cannabigerol (CBG), and cannabinol (CBN) have been reported to exhibit anti-inflammatory properties and show protective effects in experimental models of intestinal inflammation (Borrelli et al., 2013; Li et al., 2024; Sepulveda et al., 2024).

Gut microbiota and gastrointestinal relevance in ruminants and poultry

The gut microbiota, a complex ecosystem of host-associated microorganisms, plays established roles in metabolic regulation, immune function, and intestinal barrier integrity. Its composition varies substantially across animal species, and these differences carry direct functional implications for how diet-mediated effects may manifest in different production contexts.

In ruminants, the gastrointestinal microbial ecosystem is predominantly situated within the rumen, where cellulolytic microorganisms are predominant and aid in the breakdown of cellulose and other complex plant polysaccharides. The ruminal microbiota comprises eight bacterial phyla, which collectively account for approximately 99% of the sequences observed in 16S rRNA sequence analyses. Among these, Bacteroidota, particularly Prevotella spp., and Firmicutes, including Butyrivibrio and Ruminococcus spp., are recognized as dominant phyla (Henderson et al., 2015; Mizrahi et al., 2021). Key cellulolytic bacteria such as Fibrobacter succinogenes and Ruminococcus flavefaciens play a crucial role in fiber digestion (Mizrahi et al., 2021) while methanogenic archaea are responsible for methane synthesis (St-Pierre et al., 2015). Rumen microorganisms also participate in broader physiological processes including nitrogen cycling and host energy utilisation, making the ruminal microbiota central to animal productivity (Liang et al., 2024). In poultry, the gut microbiota contributes to digestive efficiency, immune function, and resistance to pathogen colonization (Choi et al., 2014; Oakley et al., 2014). The cecal microbiome is dominated by Firmicutes and Bacteroidetes, which together constitute 75–95% of classified sequences (Aruwa et al., 2021; Kers et al., 2018). Within Firmicutes, Lactobacillaceae, Lachnospiraceae, and Ruminococcaceae are the most prominent families (Aruwa et al., 2021; Vacca et al., 2020), while Proteobacteria, including potentially pathogenic genera such as Escherichia, Campylobacter, and Salmonella, remain below 10% in healthy birds but expand during dysbiosis (Yue et al., 2024). These compositional characteristics are directly relevant to interpreting hemp supplementation effects, as the primary outcomes reported in poultry studies, increased Lactobacillus abundance, reduced E. coli counts, and altered short-chain fatty acids (SCFAs) profiles, reflect shifts within this established microbial framework.

Beyond structural composition, the gut microbiota in both species contributes to core physiological functions that are directly relevant to the outcomes observed in hemp supplementation studies. The gut microbiota contributes to a broad range of physiological processes, including the production of SCFAs via fermentation of complex carbohydrates (Flint et al., 2012), preservation of epithelial barrier integrity through regulation of tight junction proteins (Ulluwishewa et al., 2011), and modulation of mucosal and systemic immune responses (Belkaid and Hand, 2014). In recent years, an increasing number of studies have explored the interactions between cannabinoids and microbiota (Varsha et al., 2022). However, comparing findings across animals can present challenges due to significant variability in microbiota composition and the distinct metabolic and immune response capacities of each species (Tang et al., 2026). Consequently, effects observed in one production system cannot be directly extrapolated to another, and species-specific interpretation remains essential when evaluating the gastrointestinal responses of ruminants and poultry to dietary hemp compounds.

Hemp-derived feed ingredients and products for animal nutrition

Industrial hemp has gained increasing attention as a sustainable feed resource due to its high nutritional value and the availability of multiple co-products generated during seed oil processing and cannabinoid extraction. The most common hemp-derived feed ingredients include whole hemp seeds, hemp seed meal (also referred to as hemp seed cake), hemp seed oil, and spent hemp biomass from cannabinoid extraction, all of which have been investigated in different animal production systems (Irawan et al., 2025). Hempseed and its derived fractions represent a nutritionally valuable and increasingly relevant option in animal feeding. Hemp seeds typically contain 20–25% highly digestible protein, characterized by albumin and a well-balanced profile of essential amino acids, including arginine, methionine, and cysteine (Fallahi et al., 2022). They also provide 25–35% carbohydrates, significant levels of vitamins, particularly γ-tocopherol (~60.85 mg/100 g dry matter), and a range of essential minerals. Hempseed meal, in particular, contains elevated protein levels (typically 30–50%). The lipid composition is dominated by six major long-chain fatty acids: palmitic acid (6.73–7.75%), stearic acid (2.26–2.69%), oleic acid (12.77–13.98%), linoleic acid (53.82–56.55%), γ-linolenic acid (1.83–5.45%), and α-linolenic acid (14.60–16.84%). This profile results in an advantageous omega-6 to omega-3 ratio of approximately 3–3.5:1, making these products increasingly considered viable alternatives to conventional plant-based feed ingredients (Finet et al., 2023; Irawan et al., 2025).

In ruminant nutrition, hemp seed meal and cake have been extensively evaluated as alternative protein sources for cattle, sheep, and goats. Their excellent nutritional profile allows them to partially replace conventional sources like soybean meal, canola meal, dried distillers’ grains, and alfalfa (Irawan et al., 2025). Importantly, hemp-derived lipids may influence milk and meat fatty acid composition by increasing beneficial PUFAs, including omega-3 fatty acids. Nevertheless, the use of these by-products in ruminant feed may remain limited by THC and CBD residues. No harmonised maximum residue limit for cannabinoids in ruminant meat or milk has been established across major jurisdictions; Switzerland has set a food product threshold of 10 ppm total THC, but no equivalent standard exist for ruminant products. Smith et al. (2023) detected no CBD or THC in muscle, liver, or kidney of heifers fed 20% hempseed cake for 111 days, with only trace levels in adipose tissue (6.3–10.1 ng/g) well below the EFSA acute reference dose (ARfD) of 0.001 mg THC/kg body weight, and Ran et al. (2024), similarly found no cannabinoid residues in meat of hemp-supplemented goats. Milk presents a greater concern: Wagner et al. (2022) detected up to 316 µg ∆9-THC/kg milk from dairy cows fed cannabinoid-rich hemp, with a feed-to-milk transfer rate of approximately 0.2%, concentrations that significantly exceeded the ARfD for several consumer groups, particularly children, making product-specific risk assessment essential when cannabinoid-rich hemp ingredients are used in lactating dairy cow diets.

In poultry production, hemp derivatives have been extensively investigated as sources of essential fatty acids and plant protein. The American Association of Feed Control Officials (AAFCO) has formally approved hemp seed meal for use in laying hen feeds (up to 20% inclusion) with strict limits of ≤2 ppm THC and ≤20 ppm CBD, marking the first federally approved hemp-based feed ingredient in the United States.

Research on laying hens and broiler chickens indicates that hemp derivatives can be safely utilized in poultry feed formulations. For laying hens, hemp seed inclusion at 20–25% does not impair health or productivity (Shariatmadari, 2023). Hemp seed cake or meal has also been evaluated at 15–20% inclusion levels, with no major adverse effects on laying rate or egg weight reported in several studies (Lanzoni et al., 2024). Furthermore, hemp oil has been tested mainly at 4–12% inclusion levels, showing improved egg yolk fatty acid profiles without consistent negative effects on laying performance (Lanzoni et al., 2024). For broilers, responses are product- and condition-dependent even within the same ingredient category: Eriksson and Wall (2012) reported no impairment of growth performance with hemp seed cake at tested inclusion levels (10-20%, organic production), whereas Darmawan and Ozturk (2025) found that 15% hemp seed cake was associated with reduced final body weight, poorer feed conversion, and decreased villus height and surface area, indicating that outcomes vary depending on experimental conditions.

Although direct evidence on hemp-specific applications in livestock remains limited, the combined nutritional profile and bioactive constituents of hemp, including dietary fiber, polyunsaturated fatty acids, and phytocannabinoids, suggest a potential role in modulating gastrointestinal function. In particular, these components may interact with gut microbiota and intestinal physiology; however, current evidence is still fragmented and largely indirect. Therefore, a comprehensive evaluation of the effects of hemp-derived ingredients on gut microbiota is needed to better understand their functional implications in animal nutrition.

Effects of hemp and cannabinoids on gut microbiota in ruminants

The genus Methanobrevibacter constitutes a significant proportion of the rumen archaeal community (60–70%) and is classified into two primary subclades: the ‘high-methane’ smithii–gottschalkii–millerae–thaurei (SGMT) group and the ‘low-methane’ ruminantium–olleyae (RO) group. Research indicates that these clades are associated with distinct methane emission phenotypes (St-Pierre et al., 2015). The interplay between protozoa and methanogenic archaea is particularly noteworthy; defaunation studies suggest that the removal of protozoa can lead to a reduction in methane emissions (Wallace et al., 2015). Additionally, compounds such as rumen terpenes and polyphenols are recognized for their potential to suppress microbial populations (Ku-Vera et al., 2020), forming a theoretical basis for the methane mitigation capabilities of plant-derived secondary metabolites.

In light of this, the impact of hemp and its by-products on rumen microbiota and fermentation processes has been the focus of investigation. In research utilizing whole hemp biomass, Cannabis sativa residue (CSR) powder, and hemp essential oils, a notable finding across both in vivo and in vitro models (Table 2) is the observed increase in ruminal propionate levels, accompanied by a reduction in the abundance of methanogenic archaea or methane production (Hnokaew et al., 2025; Ran et al., 2024; Silva et al., 2023). In vitro studies indicate that hemp-derived essential oils and cannabinoids can influence the rumen bacterial community and may help reduce methane production (Silva et al., 2023; Tabiś et al., 2024). In vivo research has demonstrated that the incorporation of hemp seed cake or green hemp biomass can modify rumen fermentation parameters, microbial composition, and nutrient digestion in ruminants (Fruge et al., 2025; Ran et al., 2024; Stevens et al., 2022; Wang et al., 2023; Winders et al., 2023a, b). Across studies employing 16S rRNA amplicon sequencing, beta diversity shifts indicate that hemp supplementation reorganises community composition without reducing overall microbial richness, a pattern functionally distinct from a diversity-depleting intervention. Notably, alterations in populations of Prevotella, Ruminococcus, and methanogenic archaea suggest a possible association with reduced methane production under specific experimental conditions within the rumen microbial ecosystem (Irawan et al., 2025; Winders et al., 2023a).

Observed modifications in microbial taxa such as Succinivibrionaceae, Prevotella, and Lachnospiraceae, alongside increased propionate and decreased methane production across independent studies using different hemp products (Hnokaew et al., 2025; Ran et al., 2024; Silva et al., 2023; Tabiś et al., 2024), are consistent with the well-established rumen fermentation principle that propionate synthesis and methanogenesis compete for available metabolic hydrogen (Hnokaew et al., 2025; Ku-Vera et al., 2020; Wallace et al., 2015). The convergence of this pattern across methodologically distinct studies strengthens the mechanistic inference; however, as no study in the reviewed literature directly measured dissolved hydrogen partial pressure or quantified hydrogen flux through competing pathways in hemp-fed ruminants, a causal relationship cannot yet be confirmed. Hnokaew et al. (2025) reported a 34–38% reduction in in vitro methane production and a significant increase in the propionic acid molar proportion at 1–2% CSR inclusion, accompanied by decreased Methanobacteriales abundance; CBD and THC in CSR were further shown by molecular docking to bind the active site of methyl-coenzyme M reductase with binding energies of −8.8 and −5.5 kcal/mol, respectively.

Hemp-related secondary metabolites, particularly terpenes such as E-Β-caryophyllene, α-pinene, and Β-myrcene, have the capacity to directly inhibit specific rumen microorganisms, including those implicated in methanogenesis. This potential mechanism may elucidate why whole-plant extracts or fractions rich in essential oils frequently produce more consistent outcomes than isolated cannabidiol. Supporting this hypothesis, Tabiś et al. (2024) quantified terpene profiles by GC-MS and found E-Β-caryophyllene to be the predominant compound in Cannabis essential oils (18.4% in Cannabis sativa, 24.1% in Cannabis indica), alongside α-pinene and Β-myrcene, and demonstrated that these oils alter rumen microbial populations and reduce methane production in vitro. However, the remaining ruminant studies reviewed here characterized their hemp products for cannabinoid and nutritional content only, without reporting terpene profiles; the role of terpenes in the fermentation effects observed in those studies therefore remains speculative and warrants direct investigation through standardized phytochemical characterisation.

The currently available evidence indicates that hemp-based feeds and cannabinoid-containing products may influence selected fermentation outcomes through shifts in specific components of the ruminal microbial ecosystem (Ran et al., 2024; Silva et al., 2023; Wang et al., 2023; Winders et al., 2023b)

Table 2: Summary of the effects of cannabinoid and hemp applications in ruminant and poultry.

Animal species	Sample size/ duration	Product/ Cannabinoid	Method	Key microbiota findings	Other Key Results	Reference
Ruminants
Beef cattle (Angus cross heifers)	n=16 111 days	Hempseed cake (20%)	16S rRNA amplicon sequencing, MCC; Tukey HSD and Benjamini–Hochberg	Rumen beta-diversity altered (R²=0.06–0.12, p<0.05), Shannon diversity ↑ (p<0.05); dominant phyla Bacteroidota (62.2%), Firmicutes (16.9%), Proteobacteria (16.3%)	Nasopharyngeal microbiota also significantly affected, suggesting gut–respiratory linkage	Winders, Holman, et al. (2023a)
Dairy cattle (Holstein)	n=9 21 days	Industrial hemp ethanol extraction byproduct (11%)	16S rRNA amplicon sequencing, CC; Duncan's multiple range tests	Alpha diversity: no change (p>0.10), Rumen: Bacteroidota, Fibrobacterota, Prevotellaceae ↑; Firmicutes ↓, Feces: Firmicutes, Lachnospiraceae, Monoglobaceae ↑	Butyrate (-19.3%) and total VFA (-19.9%) ↓; milk yield and digestibility unaffected; CBD/THC not detected in milk	Wang et al. (2023)
In vitro rumen model, (Brahman x Thai Indigenous)	In vitro	Cannabis sativa L. residue powder (2%)	qPCR MCC; Duncan's multiple range tests	Ruminococcus flavefaciens ↓ , Methanobacteriales ↓, p<0.05, exact fold NR	Methane production (-35%) ↓, Acetate /Propionate ↓, Propionate ↑, NH₃-N ↑, exact ratio NR	Hnokaew et al. (2025)
In vitro rumen model (Angus × Holstein steers)	In vitro	CBD (different concentrations)	Culture MCC; Tukey HSD	The viable cell count of hyper-ammonia-producing bacteria and generalist amino acid-fermenting bacteria remained unchanged	Ammonia production: ↓ by ~10–15 mM at highest concentration (860 μg/mL) (p < 0.05)	Lakes et al. (2024)
In vitro rumen model	In vitro	CBD (different concentrations; hemp varieties) and alfalfa	16S rRNA amplicon sequencing, MCC; ANCOM testing	Alpha diversity: alfalfa highest; no difference between CBD levels Beta diversity: alfalfa clustered separately from all hemp groups. Dominant phyla: Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria Alfalfa > Hemp: Aerococcaceae and Enterobacteriaceae Alfalfa < Hemp: Lactobacillales, Streptococcaceae, Succinivibrionaceae, Bacilli	No diversity differences between CBD levels; substrate type (alfalfa vs hemp) more influential than CBD concentration on microbiome structure	Silva et al. (2023)*
In vitro rumen model	In vitro	Essential oils (EOs) from Cannabis sativa and Cannabis indica (50 µL or 100 µL)	qPCR MCC; Bonferroni	Modulation of rumen microbial populations; notable effects on Lactobacillus spp. (p<0.01) and Butyrivibrio spp. (p<0.05) ↓	Acetate (↑,6h, +15.4%, C. Indica 100 µL) and Propionate (↑,6h, +3%, C. Indica 100 µL) Acetate/propionate ratio ↓, 24h, C. indica 100, -20%, p<0.05). Methane production (↓, 6h, -27.7%, C. Indica 100 µL)	Tabiś et al. (2024)
Goats (Xiangdong black goats)	n=10 60 days	Hemp forage (stems and leaves; 5%, 10%, or 20% in diet, substituting alfalfa hay)	16S rRNA amplicon sequencing MCC; NR	Alpha diversity: No effect (p>0.05); Prevotella_1 ↓ (p=0.040, exact ratio NR), Rikenellaceae_RC9_gut_group ↑ p=0.017, exact ratio NR), Tenericutes ↑	In 20% hemp forage group FCR ↓ (-18.4%), NH₃-N ↑ (+25.1%) ↓, Propionate ↑ (+15.2%), VFAs ↑ (+34.4% in 10% hemp forage group), cannabinoids/metabolites detected in rumen fluid and plasma; none detected in meat.	Ran et al. (2024)
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Animal species	Sample size/ duration	Product/ Cannabinoid	Method	Key microbiota findings	Other Key Results	Reference
Goats (Alpine dairy goats)	n=6 140 days	Hemp seeds (9.3%)	16S rRNA amplicon sequencing MCC; NR	Hemp did not significantly alter major bacterial genera	ruminal linoleic acid ↑ (+63%), milk fat ↑ (from 3.39% to 3.69%)	Cremonesi et al. (2018)
Buffalo (dairy crossbred)	n=5 42 days	Hemp seed oil	16S rRNA amplicon sequencing MCC; NR	Alpha diversity: No effect Engyodontium ↑ (p=0.047) and Sarocladium ↑ (p=0.031)	Lactic acid ↑ (+80.5%), Acetate /Propionate ↓ (-21.4)	Zhou et al. (2022)
Poultry
Ross 308 line male broilers (C. perfringens-challenged)	n=72 8 replicates 35 days	CBD (15 g/kg)	qPCR MCC; LSD	Abundance of Total bacteria, C. perfringens, Lactobacillus spp. Bifidobacterium spp. not changed in cecal digesta	ADG and final BW not changed	Kinsner et al. (2025)
Ross 308 line male broilers	n=25 42 days	10-30 g/kg Hemp leaves (242.5 µg/kg CBD)	Culture MCC; Bonferroni	Faecal E. coli ↓ (p<0.0001, from 5.53 to 3.13 log10 CFU)	CD4+ lymphocyte ↑ (p<0.0001, exact ratio NR), CD8+ lymphocyte ↑ (p<0.0001, exact ratio NR)	Balenović et al. (2024)
Unsexed Ross 308 broilers	n=30 6 replicates 42 days	Hemp seed cake (15%), autoclaved (120°C)	Culture MCC; Duncan's multiple range tests	Caecal E. coli ↓(p<0.01, from 4.00 to 3.47 log10 CFU) , Lactobacillus acidophilus ↑ (p<0.01, from 3.62 to 4.32 log10 CFU)	Final BW ↓ (-22.1%, p<0.01) , FCR ↑ (+17.8%, p<0.01), villus height (-31.3%, p<0.01) and surface area ↓ (45.9%, p<0.01)	Darmawan and Ozturk (2025)
Caribro-Vishal broiler chicks	n=32 4 replicates 42 days	Hemp seed (0.2-0.3%)	Culture MCC; Tukey HSD	Jejunal total coliforms ↓(p<0.01, from 7.32 to 6.35 log10 CFU) Caecal total Lactobacillus spp. ↑ (p<0.001, from 7.90 to 8.61 log10 CFU)	ADG, final BW and intestinal histomorphology not changed	Vispute et al. (2019)
In vitro cecal fermentation by broiler microbiota	In vitro	Micronized hemp fiber (0.75-1.5%)	Culture MCC; Duncan's multiple range tests	Total bacteria ↑ (p=0.005, from 9.10 to 9.30 log10 CFU), Lactobacillus spp. ↑ (p=0.001, from 8.10 to 8.60 log10 CFU), Enterococcus spp. ↑ (p=0.001, from 7.20 to 7.90 log10 CFU), E. coli ↓ (p=0.001, from 5.30 to 4.50 log10 CFU),	Lactic acid: ↑ (+19.6%, p=0.006); total VFA: ↑ (+28.4%, p=0.004); acetic acid: ↑ (+19.9%, p=0.002); propionic acid: ↑ (+22.9%, p=0.001); butyric acid: ↑ (+42.9%, p=0.001); final BW: ↑ (+13.7%, p<0.001); ADG: ↑ (+19.5%, p<0.001); FCR: ↓ (-14.3%, p<0.001)	Incharoen et al. (2025)
Ross 308 hybrid cockerels	n=50 37 days	2.5% Hemp seed expellers (0.03% CBD) or 1% hemp plant tops (0.015% CBD)	Culture MCC; Scheffé's test	Ileal E. coli, Lactobacillus spp. and Enterococcus spp not changed	FCR and final BW not changed	Šťastník et al. (2016)*
Unsexed Ross 308 broilers, organic production	n=600 70 days	Hemp seed cake (10% for starter-20% for finisher)	Culture MCC: not required	Caecal content of C. perfringens not changed	FCR and final BW not changed	Eriksson and Wall (2012)

Average daily gain: ADG, Body weight: BW, Cannabidiol: CBD, cluster of differentiation: CD, Feed conversion ratio: FCR, Volatile fatty acids: VFA, Δ9-tetrahydrocannabinol: THC, not reported: NR, MCC: Multiple comparison correction, * Conference paper

and modulation of microbial metabolic activity (Hnokaew et al., 2025), with the relative contribution of each pathway remaining unclear given the heterogeneity of available evidence. Interpretation remains difficult because product composition, dietary background, and analytical methodology vary substantially across studies, and no published study has directly measured ECS receptor activation as a mechanistic endpoint in the context of dietary hemp supplementation in ruminants. Accordingly, the present evidence base is insufficient to support the use of hemp-derived products as microbiota-targeted interventions in ruminant nutrition. Until controlled in vivo trials with standardised hemp preparations, quantified cannabinoid profiles, and direct microbiota endpoints, including, where feasible, receptor-level measurements, are conducted across multiple ruminant species, the fermentation and community composition changes reported to date should be interpreted as preliminary observations rather than actionable findings (Table 2).

Effects of hemp and cannabinoids on gut microbiota in poultry

Broiler production constitutes a significant sector for hemp-based feed supplementation, particularly in response to industry-wide pressures to diminish prophylactic antibiotic usage in accordance with global antimicrobial stewardship initiatives. Of the poultry studies reviewed, four reported reductions in E. coli or coliform counts and three reported increases in Lactobacillus populations (Balenović et al., 2024; Darmawan and Ozturk, 2025; Incharoen et al., 2025; Vispute et al., 2019), while one reported no change in Lactobacillus or C. perfringens abundance under CBD supplementation (Kinsner et al., 2025).

The effects of hemp derivatives on gastrointestinal health and the microbiota warrant further investigation. Some studies suggest that hemp productsmay not substantially affect the gut microbiota (beneficial or pathogenic) (Eriksson and Wall, 2012) whereas other findings indicate a potential role in promoting beneficial bacteria (Vispute et al., 2019). These different results could be due to differences in how the products are made, how much is administered, the age of the animals being tested, and the experimental conditions. In broiler chickens, inclusion of hemp seed meal and micronized hemp fiber significantly increases Lactobacillus populations while reducing Escherichia coli counts in the cecum (Darmawan and Ozturk, 2025; Incharoen et al., 2025). Hemp fiber may act via a possible prebiotic-like mechanism by supporting saccharolytic fermentation (Nissen et al., 2023), thereby enhancing Lactobacillus spp. populations and increases the production of lactic acid and short-chain fatty acids. This process potentially lowers luminal pH and suppresses pathogen growth, as suggested by Incharoen et al. (2025). In broiler chickens, micronized hemp fiber supplementation at 0.75–1.50% of diet significantly increased in vitro cecal SCFA concentrations (p < 0.01): total VFA increased from 29.2 to 37.5 mmol/mL (+28%), driven by +20% acetic acid, +23% propionic acid, and +43% butyric acid (Incharoen et al., 2025).

CBD supplementation has been evaluated under C. perfringens challenge models designed to mimic necrotic enteritis. CBD exerted its effects mainly through modulation of intestinal barrier function, immune responses, and oxidative status (Bień et al., 2024). CBD administration was linked to changes in tight-junction-related markers and expression and shifting bacterial enzyme activity toward increased energy uptake (Konieczka et al., 2020). Hemp bioactives may indirectly support intestinal health by modulating immune functions in immune tissues rich in CB2R receptors, such as the gut-associated lymphoid tissue in chickens (Ghazi et al., 2026). In this context, the immunomodulatory role of CB2R described by Turcotte et al. (2016), along with the increased CD4+ and CD8+ lymphocyte responses observed in broilers by Balenović et al. (2024), suggests that some microbiota-related benefits might arise not only from direct antimicrobial actions but also from improved mucosal immune surveillance. Sopian et al. (2024) reported that Cannabis sativa residue supplementation at 1% of diet significantly improved the villus height-to-crypt depth ratio in the ileum (p = 0.011) and reduced plasma malondialdehyde and total bilirubin concentrations, suggesting improved intestinal morphology and oxidative stability without adverse effects on growth performance or blood biochemistry at inclusion levels of 0.5–2%. Sana et al. (2024) reported that hemp seed inclusion at 15–20% significantly increased white blood cell counts (p = 0.037) and transiently elevated IgM and IgG production at 20% inclusion on day 28 (p= 0.021); however, these immune effects were not sustained to day 35, and jejunal histomorphology, including villus height, width, and crypt depth , was not significantly affected at any tested inclusion level (p > 0.05), with only a non-significant numerical trend toward increased villus height at higher inclusion levels.

The mechanism underlying CBD-mediated improvement of intestinal barrier function in poultry is not fully established. Szkopek et al. (2024) provided the most direct poultry-specific mechanistic evidence to date, demonstrating that CBD significantly modulates PPARα expression in the broiler gut under both C. perfringens and LPS challenge conditions (p = 0.001), with PPAR activity positively correlated with tight junction gene expression. Cannabidiol-mediated improvement of intestinal barrier function may operate through targets such as TRPV1, GPR55, and inflammation-related signaling cascades (Brown et al., 2024), thereby supporting tight junction integrity and making epithelial colonization more difficult for opportunistic pathogens; this interpretation is consistent with the findings of Konieczka et al. (2022) in challenged chickens and with the barrier-protective effects of CBD on intestinal cells described by Boehm et al. (2023). However, TRPV1 and GPR55 have not been confirmed by receptor blockade studies in poultry and remain working hypotheses derived from mammalian pharmacology.

The poultry studies (Table 2) exhibit a more heterogeneous pattern than the ruminant data, reflecting greater diversity in hemp preparation type, inclusion level, and microbiota assessment methodology. Future studies should preferentially employ 16S rRNA amplicon sequencing (V3–V4 or V1–V3 regions) as a minimum standard for microbiota characterization to enable cross-study comparability and robust taxonomic resolution. The existing literature indicates that research on the effects of hemp-derived products on gastrointestinal microbiota and intestinal health in poultry has predominantly focused on broiler chickens, while data on laying hens remain limited (Table 2). Furthermore, microbiota-related evidence for other poultry species such as quail, turkey, goose, and duck is absent. In addition, current evidence is largely restricted to CBD and hemp seed by-products, and no published data exists on the effects of THC or minor cannabinoids on the poultry gut microbiota.

Limitations

Several methodological and empirical limitations impede our current understanding and render it challenging to draw definitive conclusions from existing research. Firstly, the available mechanistic evidence on cannabinoid–microbiota interactions in farm animals remains limited; this gap reflects the deliberate scope of the present review, which focuses on ruminants and poultry rather than extrapolating from preclinical mammalian models. Future studies should directly examine cannabinoid–microbiota mechanisms in the species relevant to livestock production. Secondly, most in vivo studies employed limited sample sizes and short durations. For cattle, the median sample size was 12.5 animals per group (range 9–16) and median duration was 66 days (21–111). For goats, median n=8 (6–10) and 100 days (60–140). For broilers, median n= 41 (25–600) and 42 days (35–70). These limited scales constrain insights into long-term microbiota adaptations and inter-individual variability (Table 2). Thirdly, a prevalent issue involves inconsistent standardization of preparations derived from hemp: discrepancies in botanical sources, extraction techniques, purity levels, and phytocannabinoid profiles across studies hinder direct comparisons. Seven studies reported only primary cannabinoid content (CBD and/or THC), and a single study (Tabiś et al., 2024) performed terpene profiling by GC-MS; the remaining studies supplied no chemical characterization at all. Fourthly, the use of diverse microbiota assessment methods, including 16S rRNA sequencing, qPCR, and culture-based techniques, introduces substantial methodological heterogeneity and limits direct comparability across studies. We therefore did not exclude studies based on methodology alone, as the current literature remains too limited to permit such filtering without losing relevant evidence. While this inclusive approach is appropriate for a narrative review, it precludes meta-analysis and prevents any claim of quantitative synthesis. Finally, the available livestock studies do not provide sufficient paired data on gastrointestinal cannabinoid exposure and microbiota outcomes to assess concentration–response relationships. This absence of segment-specific exposure data limits mechanistic interpretation and should be addressed in future studies. Consequently, the mechanistic relationship between bioavailability and microbial response remains inadequately elucidated.

Future directions

Despite increasing interest in the therapeutic and nutritional advantages of hemp-derived compounds, limited evidence remains regarding their impact on the gut microbiota of livestock animals. The effect of feeding hemp and its by-products on the animal microbiome is still insufficiently characterized, with extant research primarily concentrating on digestibility and growth performance rather than microbiome alterations. Furthermore, current available microbiome data are largely restricted to ruminants and poultry, thus leaving a substantial knowledge gap concerning monogastric animals such as pigs and horses. Future research should endeavor to execute controlled trials in pigs and horses employing techniques such as 16S rRNA sequencing and shotgun metagenomics. The hemp–microbiota interplay represents an emerging candidate mechanism, but current livestock evidence remains insufficient for routine application. Preliminary findings suggest Lactobacillus enrichment and E. coli suppression in poultry, together with SCFA and fermentation-related modulation in ruminants. However, practical antibiotic-sparing or sustainable production applications require confirmation through standardized, species-specific controlled trials.

Conclusion

The current evidence indicates that dietary hemp derivatives may affect certain microbiota-related outcomes in ruminants and broilers, but the effects are species-, product-, and context-dependent. In broilers, the most common findings are reductions in E. coli or coliform counts and increases in Lactobacillus abundance following supplementation with hempseed products or hemp fiber. In ruminants, the most reported effects are changes in rumen fermentation, SCFA profiles, microbial groups involved in methanogenesis, and microbial community composition. Hempseed cake may be considered for use as a partial protein source for broilers only after product-specific formulation, regulatory compliance, and performance monitoring. For ruminants, no clear microbiota-based recommendation can be made at present because of heterogeneous fermentation responses and unresolved safety concerns regarding cannabinoid residues, particularly in milk. Future studies should address standardization of hemp product characterization, defined inclusion criteria, adequate sample size and experimental duration, comparable microbiota assessment methods, and concurrent phytochemical and performance analyses.

Acknowledgement

The authors have no acknowledgements to declare.

Novelty Statement

This review provides a focused synthesis of the dietary hemp–gut microbiome interplay in ruminants and broilers by integrating evidence on microbial composition, fermentation, intestinal barrier function, and endocannabinoid-related mechanisms.

Author’s Contribution

ES wrote the original draft and reviewed the manuscript. SBS wrote parts of the original draft and reviewed the manuscript. All the authors read and approved the final manuscript.

Data availability

Not applicable, as it is a review article and no datasets were generated.

Generative AI and AI assisted technology statement

The authors utilized generative artificial intelligence (AI) exclusively for language editing and grammatical corrections.

Conflict of interest

The authors have declared no conflict of interest.

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