Δ9-tetrahydrocannabinol and cannabidiol resist rumen microbial metabolism but impair feed digestibility and alter volatile fatty acid profiles

Context Industrial hemp biomass, the low Δ9-tetrahydrocannabinol variety of Cannabis sativa L., was identified as a potential feed for ruminants because of its quick growth rate and high biomass yield. Industrial hemp biomass was found to be nutritionally suitable for sheep following feeding either iHemp stubble- or hay-containing diets; however, the potential effects the cannabinoids present in industrial hemp biomass, including both Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD), may have on the consuming animal remain largely unknown. Aims The aim of this study was to determine whether Δ9-THC and/or CBD are metabolised in the rumen, affect the rumen environment, and/or the 24 h digestibility of a feed standard. Methods Daisy™ incubators designed for the efficient laboratory simulation of ruminant digestion in vitro were utilised, with the study consisting of three treatment groups (1, dimethyl sulfoxide (DMSO) only; 2, CBD and DMSO; and 3, Δ9-THC and DMSO), and four replicates per treatment. Over a 24 h incubation period, the incubation medium was sampled to determine diurnal cannabinoid concentrations and volatile fatty acid (VFA) concentrations and molar proportions. At the end of the incubation period, the incubated lucerne hay standard was analysed to determine 24 h digestibility. Key results There was no evidence that either Δ9-THC or CBD are metabolised by ruminal microorganisms. Mean total VFA concentrations were unaffected; however, dry matter, organic matter and crude protein 24 h digestibility were all decreased following addition of either Δ9-THC or CBD to the incubation medium. Conclusions Metabolism of the cannabinoids must occur in an alternate location in ruminants, such as the liver, with further research required to confirm. Both Δ9-THC and CBD exert an adverse effect on digestibility, which has implications for iHemp to be a feed for production animals. Implications If industrial hemp is to be a feed for ruminants, more research is required to determine maximum concentrations of cannabinoids that ruminants could consume without causing any adverse effects on the animal, their microbial populations and, consequently, production characteristics.