Ensiling conditions and changes of cannabinoid concentration in industrial hemp

Hemp (Cannabis sativa L.) is an important source of fibre and seed oil and protein. By-products of industrial hemp fibre production, like hemp seeds and cakes, can be used as feed for all animal species as fat and protein source and the whole hemp plant (including stalk and leaves) might be a suitable fibre source for ruminants. However, a previous feeding experiment with leaf-flower-seed hemp silage, made from an industrial hemp variety, demonstrated detrimental effects on cow health parameters and a significant transfer of several cannabinoids, including the psychoactive tetrahydrocannabinol (∆9-THC), into cow's milk, posing a potential risk to the safety of consumers. Based on those observations, the present study tested the hypothesis that anaerobic fermentation, as during ensiling, increases the content of ∆9-THC in hemp. Therefore, silages of whole plants from the industrial hemp Cannabis sativa L. var. Ivory were prepared in a multifactorial design, with the four treatments 1) untreated control (CON), 2) addition of 10 mL per kg fresh weight homofermentative lactobacilli at 10⁵ cfu/mL (LBAC), 3) addition of 10 mL per kg fresh weight homofermentative lactobacilli at 10⁵ cfu/mL plus 30 g molasses (LBACmol) and 4) addition of propionic acid (10 mL/kg fresh weight) (PRO). Ultra high performance liquid chromatography coupled with tandem mass spectrometry with electrospray ionisation (UHPLC-MS/MS) was performed for analysis of cannabinoids in fresh hemp material and after 10 and 90 days of ensiling. The study revealed that ensiling decreased all acid forms of analysed cannabinoids in hemp at about 40-65% of the initial values after 90 days of storage, with the exception of cannabinolic acid (CBNA), and CBGA, the acidic form of cannabigerol (CBG). This decrease in most acidic forms was accompanied by an increase of the corresponding non-acidic forms of all cannabinoids, including the psychoactive ∆9-THC. Thus, although ensiling decreases the total cannabinoid content, psychoactive compounds like ∆9-THC can increase, enhancing the risk for animal health and a transfer of these substances into animal derived products.