PSIII-15 The effect of partial replacement levels of steam-flaked corn with high moisture rolled sorghum grain on total tract digestibility of finishing steers.

Abstract The objectives were to evaluate the effects of partially replacing steam-flaked corn (SFC) with high moisture rolled sorghum grain (HMRS) on dry matter intake (DMI) and total tract DM digestibility of finishing diets. High-moisture sorghum grain was harvested in the Texas Panhandle with 28% humidity. The grain was rolled and bagged using a roller mill bagger (Richiger R990MXPlus) with 4 roller mills set at 1 mm of distance and stored in a 2.7 m bag for 10.3 months. The average berry processing score of four samples (% of starch passing through 2.36 mm sieve) was 47%. Twelve cannulated Angus steers (BW = 774 ± 63 kg) were randomly assigned to quadruplicated 3 × 3 Latin Squares (LS) to assess the effects of partially replacing steam-flaked corn with high-moisture rolled sorghum, at levels of 0%, 25% and 50% replacement. Steers were assigned to one of three dietary treatments: 1) HMRS0 – control diet containing 63.3% SFC, 20% Sweet Bran, 11% corn stalks, 3% mineral/vitamin premix, 2% corn oil, and 0.7% urea; 2) HMRS25 – 25% of SFC replaced with HMRS; and 3) HMRS50 – 50% of SFC replaced with HMRS. Steers were fed once daily ad libitum, and feed refusals were collected and weighed each morning prior to feeding to determine DM content and calculate DMI. Fecal samples were collected 3 times per day. Chromium oxide (Cr₂O₃) was used as an indigestible marker. Each day, two capsules containing a total of 15 g of Cr₂O₃ were administered into the ventral sac of the rumen—one in the morning and one in the afternoon—beginning 10 days before the sampling period and continuing until the final day. Fecal samples were sent to NDSU Nutrition Laboratory to assess fecal chromium concentration (spectrophotometric method). Data was analyzed using the mixed model ANOVA analyses (MIXED procedure of SAS). Treatment was used as the predictor variable, and random effects were LS, period (LS), and steer (LS). There was no difference between treatment groups on DMI (P = 0.46). Compared to HMRS0 (77.2%), HMRS25 (73.4% P = 0.019) and HMRS50 (71.8% P = 0.002) had significantly lower DM digestibility. However, there was no statistical difference between HMRS25 and HMRS50 (P = 0.42). These data suggest that partially substituting SFC with HMRS may not significantly increase DMI but would reduce total tract DM digestibility.