High shear dry extruded corn in feedlot receiving diets

Two hundred twenty-six Angus crossbred steers (initial BW = 230 ± 19 kg) from a single ranch in South Dakota were enrolled in a 38-d study to evaluate the effects of a high shear dry extruded corn product on growth performance, total tract starch digestibility, and serum glucose and insulin of receiving feedlot steers. Steers were randomly allocated to pens of 6 or 7 steers per pen, with 3.66 m of linear bunk space. Dietary treatments (n = 12 pens/treatment) were initiated on d 0, including a diet with dry rolled corn (ROLL), steam flaked corn (FLAKE; 0.29 to 0.31 kg/L) or high shear dry extruded corn (EXT; Hi-Gel; Insta-Pro International; Grimes, IA). Bodyweights were measured prior to feeding at study initiation (d -1 and 0), d 17, and on d 37 and 38. On d 37, blood and fecal grab samples were collected from one steer per pen. Estimated total tract starch digestibility was calculated using the equation proposed by Zinn et al. Data were analyzed using the MIXED procedure in SAS 9.4 (SAS Institute, Cary, NC) with pen as experimental unit. Body weights were assessed using a 4% shrink to account for gut fill. Initial weights were used as a covariate in the analysis of growth performance data. Corn processing method did not influence BW, ADG, or DMI throughout the study (P ≥ 0.15). There was however, an increase in feed efficiency (G:F) in EXT compared to ROLL with FLAKE being intermediate (P = 0.007). Corn processing method influenced estimated total tract starch digestibility where EXT and FLAKE were greater than ROLL (P = 0.0002). Serum glucose and insulin were not influenced by dietary treatment (P ≥ 0.19). Weekly TMR samples were evaluated using a Penn State shaker box. There were greater particle size and more variability in the EXT TMR between week compared to ROLL and FLAKE (TRT x week P ≤ 0.04). Our results indicate the improvements in feed efficiency and estimated total tract starch digestibility offered by high shear dry extrusion are comparable to that of steam flaked corn (SFC) in diets containing 25 to 30% corn. Overall, results from this study indicate high shear dry extruded corn is a potential alternative for feedlot operators to increase starch digestion and feeding value of corn grain in feedlot receiving diets.