Effects of hops on ruminal fermentation, growth, carcass traits and shedding of Escherichia coli of feedlot cattle

Abstract

Experiments were conducted to evaluate the effects of hops on ruminal fermentation, fecal shedding of Escherichia coli and the growth of feedlot cattle. In a feedlot experiment, 60 British × Charolais steers (393 ± 3.6 kg) were randomly assigned to individual pens and fed a barley grain and barley silage-based diet for a 55-day growing and a 105-day finishing period. Hops were added to the growing diet at levels of 0, 119, 238 and 476 mg/kg dry matter (DM) and to the finishing diet at levels of 0, 238, 476 and 952 mg/kg DM. Fecal samples were collected to determine the effects of hops on shedding of E. coli. Carcass data from all steers were collected at a commercial abattoir at the end of the finishing period. Inclusion of hops in growing or finishing diets at these rates did not affect the shedding of E. coli or the feed intake, growth, feed efficiency, carcass characteristics or fatty acid composition of diaphragm tissue of steers. However, average daily gain of steers supplemented with the highest level of hops during the growing and finishing period was 6% higher ( P = 0.11) than the controls. In an in vitro experiment, DM disappearance (IVDMD) and concentration of volatile fatty acid (VFA) linearly ( P < 0.01) increased in the growing diet incubations with increasing levels of hops. Compared to the control treatment, addition of hops to the growing diet increased ( P < 0.05) gas production, VFA concentration, percentage of propionate in the total VFA and IVDMD ( P < 0.001), but lowered ( P < 0.05) the percentage of acetate and the acetate:propionate ratio. Hops added to the finishing diet linearly increased gas production ( P < 0.05). Hops at levels up to 476 mg/kg DM in a growing diet and up to 952 mg/kg DM in a finishing diet improved ruminal fermentation in vitro, but did not improve the growth or efficiency of feedlot cattle. Inclusion of higher levels of hops in the diet may be favorable for ruminant production.