Effects of bulk density of steam-flaked corn in diets containing wet corn gluten feed on feedlot cattle performance, carcass characteristics, apparent total tract digestibility, and ruminal fermentation

The effects of varying bulk density of steam-flaked corn (SFC) in diets containing wet corn gluten feed (WCGF; Sweet Bran; Cargill Corn Milling, Blair, NE) have not been defined. In Exp. 1, yearling steers (n = 108; initial BW = 367 ± 1.18 kg) were housed in 27 pens (4 steers/pen) and received 1 of 3 different SFC bulk density treatments in a randomized complete block design. Bulk density treatments were 283, 335, or 386 g/L SFC in diets containing 25% WCGF (% of DM). Steers were fed once daily to provide ad libitum access to feed for an average of 163 d. For a 5-d period before d 70 of the experiment, DMI was measured, and fecal samples were collected from each pen for measurement of nutrient digestibility using dietary acid insoluble ash as a marker. Varying bulk densities of SFC did not affect (P ≥ 0.233) overall DMI, ADG, or G:F on a live- or carcass-adjusted basis. Dressing percent and LM area increased linearly (P ≤ 0.05) as bulk density increased, but other carcass traits were not affected by treatments. Intake of DM, OM, and CP during the 5-d digestion phase did not differ among bulk densities; however, starch intake increased linearly (P = 0.004) as bulk density of SFC increased. Digestibility of DM, OM, and CP tended (P ≤ 0.065) to decrease and starch digestibility decreased (P = 0.002) linearly as bulk density of SFC increased. In Exp. 2, a 3 × 3 Latin square design was used for collection of ruminal fluid from 3 ruminally cannulated Jersey steers adapted to the same diets used in Exp. 1. Bulk density did not affect NH₃ concentrations, VFA molar proportions, ruminal fluid osmolality, and IVDMD of the diets. Total gas production increased linearly (P = 0.003) as bulk density of SFC increased from 283 to 335 g/L, but it decreased (P = 0.002) at 386 g/L. Present data suggest that bulk density can be increased up to 386 g/L in finishing diets containing 25% (DM basis) WCGF without affecting cattle performance and with limited effects on ruminal fermentation; however, digestibility of starch seemed to be affected negatively by increased bulk density in these diets.