Inhibition of growth and ammonia production of ruminal hyper ammonia-producing bacteria by Chinook or Galena hops after long-term storage

Authors: Flythe, Michael; HARLOW, BRITTANY - ORISE FELLOW; AIKEN, GLEN; GELLIN, GLORIA; Kagan, Isabelle; PAPPAS, JESSE - THE LUPULIN EXCHANGE

Submitted to: Fermentation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2017
Publication Date: 12/19/2017
Citation: Flythe, M.D., Harlow, B.E., Aiken, G.E., Gellin, G.L., Kagan, I., Pappas, J. 2017. Inhibition of growth and ammonia production of ruminal hyper ammonia-producing bacteria by Chinook or Galena hops after long-term storage. Fermentation. 3(68)1-9.

Interpretive Summary: Previous research indicates that natural chemical compounds in the hops inhibit methane and ammonia production and promote the growth of ruminant animals. The inhibitory compounds are actually the bitter acids that brewers use to flavor beer. They inhibit bacteria much in the same way as feed antibiotics, and could be used as a plant-based alternative to antibiotics (ATA). As hops age, they become less desirable to brewers. Our experiments showed that even after 5 years, carefully stored hops pellets had not lost bitter acids. The bitter acids still had antimicrobial activity, and decreased ammonia production by microorganisms from the rumen. These results indicate that the hops still possessed the activities desired in a plant-based ATA for ruminant production. Surplus hops that are not needed by the brewing industry could be used as a feed supplement for cattle and other ruminants.

Technical Abstract: Surplus hops (Humulus lupulus L.) that are not needed by the brewing industry could be used as a feed supplement for cattle and other ruminants. Previous research indicates that antimicrobial hops plant secondary metabolites (i.e. alpha- and beta-acids) inhibit methane and ammonia production and promote the growth of ruminant animals. The goal was to determine that hops pellets produced for brewing still possessed the requisite antimicrobial activity after long term storage. HPLC analysis indicated that the alpha- and beta-acid concentrations in two varieties of hops were relatively stable after 5 years of storage. Either hop variety inhibited the growth of the ruminal hyper ammonia-producing bacterium, Clostridium sticklandii SR, in broth culture and Petri plate bioassays. Either hop variety inhibited ammonia production from amino acids or peptides by mixed rumen microorganisms from Holstein steers. These results are similar to those previously obtained with fresh hops, hops extracts, other antimicrobial phytochemicals and typical feed ionophores, such as monensin. The rumen-active antimicrobial phytochemicals in hops can still be present and active after years under certain storage conditions. Further investigation is warranted to determine how surplus and older hops can be used to benefit ruminant nutrition and ruminant industries.