Effect of corn particle size with moderate amounts of wet distillers grains in finishing diets on starch digestibility and steer performance

Five hundred yearling steers (370 ± 30.0 kg, SD) were used to determine the effect of corn particle size in diets containing 35% wet distillers grains plus solubles (WDGS) on steer performance, carcass characteristics, and apparent total-tract starch digestibility (TTSD). Treatments included 45% cracked corn (CON; 2,350 μm) or finely ground corn (FIN; 500 μm) with 35% WDGS and were replicated in 4 pens per treatment with 60 or 64 steers per pen. Fecal samples were collected on d 71 and 72 (F-1) and d 102 and 103 (F-2). Final BW and HCW were heavier (P ≤ 0.01) for steers finished on CON compared with steers finished on FIN. Whereas G:F was not different (P = 0.22) between treatments, DMI and ADG were greater (P ≤ 0.01) for CON-fed steers than FIN-fed steers. Liver abscess scores were not influenced (P ≥ 0.39) by treatment. Liver abscess scores tended (P = 0.10) to influence ADG over the experiment, with steers having severe liver abscess scores gaining less compared with steers with no or mild liver abscess scores. A treatment × time effect (P < 0.01) was observed for TTSD. Whereas TTSD of steers fed CON decreased over time (90.28 and 85.74% for F-1 and F-2, respectively), TTSD of steers finished on FIN did not differ across the 2 sampling dates (97.95 and 97.55% for F-1 and F-2, respectively). Apparent starch digestibility was improved for steers fed finely ground corn with 35% WDGS; however, cattle performance was less compared with steers fed cracked corn with 35% WDGS.