Evaluation of finishing performance, carcass characteristics, acid-resistant E. coliand total coliforms from steers fed combinations of wet corn gluten feed and steam-flaked corn1

Crossbred beef steers (n = 615) were used in a 152-d experiment to compare steam-flaked corn (SFC) diets containing 0, 30, or 60% wet corn gluten feed (WCGF). On d 114 to 118, ruminal and fecal samples were collected from 180 steers and analyzed for pH, VFA, and total and acid-resistant Escherichia coli and coliforms. Acid resistance of E. coliand coliform populations was determined by exposure of the samples for 1 h in pH 2, 4, and 7 citric acid/sodium phosphate buffers. Increasing levels of WCGF linearly decreased total ruminal VFA (P= 0.01) and total fecal VFA (P= 0.06), but linearly increased ruminal and fecal acetate:propionate (P< 0.01) ratio and ruminal and fecal pH (P< 0.05). Feeding increasing WCGF levels resulted in a quadratic response (P< 0.05) with respect to numbers of ruminal E. coliand total coliform populations resistant to pH 4 exposure. Steers fed 30% WCGF had higher (0.7 log units) ruminal E. coliand total coliforms after exposure at pH 4 compared to steers fed 0 or 60% WCGF. Populations of E. coliand total coliforms at pH 2 and 7 were similar for all dietary treatments. Dietary WCGF linearly increased DMI (P= 0.07) and liver abscesses (P= 0.03) and linearly decreased dietary NEg(P= 0.02). Average daily gain and feed efficiencies were greatest when steers were offered 30% WCGF (quadratic, P< 0.05). Dietary manipulations that reduce acid concentrations may not correspond to changes in acid resistance of E. coliand total coliform populations detected in the gastrointestinal tracts of cattle. Moderate levels of WCGF complement SFC finishing diets.