Bitter but Beneficial: Hop-Based Feed Additives for Fighting Antimicrobial Resistance in Poultry

ABSTRACT Antimicrobial resistance ( AMR ) is an increasing challenge in the global production of poultry, where antibiotics have traditionally been used to promote growth. Phytogenic feed additives ( PFA s), particularly hop-based ones, could be a sustainable alternative due to their antimicrobial properties. The present study investigated two hop extracts from two sources, which are Type 90 hop pellets derived from fresh hops and residue of same hop pellets that had previously undergone CO 2 extraction, using a cross-model analysis combining in vitro (viability assay/broth dilution assay), ex ovo (shell-less hen’s egg test) and in vivo tests. Both types of extracts exhibited antimicrobial activity in vitro and high biocompatibility in the ex ovo model. Notably, the biocompatibility was improved for ex ovo setup, compared to in vitro cytotoxicity, providing important insights regarding their potential application as PFAs. For in vivo studies, hop extracts were microencapsulated as solid liquid microspheres to increase their stability and bioavailability. Feeding animals microencapsulated hop extracts or xanthohumol-rich residue from CO 2 extraction led to a significant reduction specifically of Gram-negative intestinal bacteria, with no change in animal performance. Overall, two promising products were identified that could potentially be used as a sustainable alternative to antibiotics in poultry production.