Antimicrobial properties of secondary metabolites of Cannabis sativa: A promising natural alternative for livestock health

In addition to their practical importance as a medicinal plant, animal feed and a source of materials for the textile and construction industry, industrial varieties of Cannabis sativa L. (hemp in a wider sense) provide an alternative for controlling infectious diseases in livestock. Despite the genetic divergence between two primary groups of cannabis, i.e. medicinal cannabis and technical hemp, hemp plants also produce a wide spectrum of secondary metabolites. These include the main classes of cannabinoids and terpenoids, as well as representatives of flavonoids, stilbenoids, steroids, alkaloids, spiroindans, dihydrophenanthrenes, and lignanamides. Many of them exhibit antibiotic activity which can substitute or complement the use of traditional antibiotics in animal husbandry. For example, the cannabinoid fraction exhibits activity against the Gram-positive bacteria and some fungi. While the activity against Gram-negative bacteria is not characteristic of cannabinoids, these pathogens can still be affected by hemp terpenoids and flavonoids. The synergy among the secondary metabolite fractions or between the hemp metabolites and traditional antibiotics is also a favourable factor. The search for alternatives to traditional antibiotics is further driven by the increasing prevalence of genetically determined antibiotic resistance among veterinary pathogens, which poses the additional risk of transferring resistance traits to the human pathogens. The content of antibiotically active compounds in hemp can be enhanced through selection among existing genotypes, targeted breeding, cultivation conditions, and even by specific elicitation of secondary metabolites with the natural antibiotic function in the disease resistance of the plant. The switch to hemp metabolites is also supported by their compatibility as natural components of plant-based animal feed, and by favourable economic considerations.