Hops are a key ingredient in beer-making, but could they also play a crucial role in the fight against laminitis?
Researchers have investigated whether β-acid (beta acid) from hops could be used to reduce the overgrowth of bacteria in the equine hindgut and control fructan fermentation in pasture associated laminitis. Their findings were reported in the Journal of Applied Microbiology.
Hops are the cone-like flowers of the female hop vine (Humulus lupulus). A soft resin contained in the flower is used to give beer its bitter flavour and “hoppy” aroma. Among its constituents are β-acids, such as lupulone, which inhibit the growth of beer-spoiling bacteria.
Research led by Brittany Harlow, of the Department of Animals and Food Sciences at the University of Kentucky, sought to determine if that antibacterial action could be used to limit the bacterial overgrowth that occurs in some cases of laminitis.
Another aim of the study was to verify the antimicrobial mode of action on Streptococcus bovis, which has been implicated in fructan fermentation, hindgut acidosis and pasture-associated laminitis in the horse.
Harlow and her colleagues found that when suspensions of equine faecal micro-organisms were enriched with inulin (a type of fructan) they fermented the inulin resulting in acid production and a fall in pH. But when β-acid (lupulone) was added to the culture in concentrations ≥9ppm, lactate production was inhibited and the decrease in pH was limited.
They were able to isolate inulin-fermenting S. bovis from the fermented suspension. They also demonstrated that these organisms were sensitive to beta-acids, resulting in fewer viable organisms in faecal suspensions.
When they added beta-acid to pure cultures of S. bovis, they found a reduction in bacterial growth, reduced lactate production and decreased intracellular potassium of the micro-organism.
The researchers conclude that their findings support the hypothesis that hops β-acid prevented the growth of fructan-fermenting equine faecal bacteria, and that the mechanism of action involved dissipation of the intracellular potassium of S. bovis.
They suggest that hops β-acid is a potential phytochemical intervention to decrease the growth of bacteria responsible for pasture associated laminitis.
Inhibition of fructan-fermenting equine faecal bacteria and Streptococcus bovis by hops (Humulus lupulus L.) β-acid.
Harlow BE, Lawrence LM, Kagan IA, Flythe MD.
J Appl Microbiol. 2014 Apr 29. doi: 10.1111/jam.12532