Effects of Hops (<i>Humulus lupulus</i> L.) Beta-Acids on Short Chain Fatty Acid Production from Complex Carbohydrates by Rumen Microbiota

Abstract

The aim of this experiment was to determine the effects of beta-acids, prenylated phenolic compounds from the hops plant, on fermentation of individual carbohydrates by rumen microorganisms. Mixed, uncultivated rumen microbiota was harvested from rumen fistulated steers and washed to make cell suspensions. The suspensions were used to inoculate media with a glucan, fructan or constituent sugar, and fermentation was evaluated by production of short-chain fatty acids (SCFA). Hops beta-acid (30 ppm) was not universally inhibitory, but each of the SCFA (acetate, propionate or butyrate) was decreased (P < 0.05) in one or more of each cellulose or starch tested. The fermentation of sugars and fructans (short-or long-chain inulins) was not impacted by the phytochemicals. Previous results have shown that hops and hops extracts had the beneficial effects of reducing rumen ammonia and methane. The current results indicate that both starch and cellulose fermentation could be impacted. Because cellulose fermentation is nutritionally important on forage-based diets, hops phytochemicals might have more utility in cereal grain-based rations.