PSXIII-17 - Feeding sorghum silage: effects of grain processing on intake and apparent total tract digestibility of backgrounding beef heifers

Abstract: This study evaluated the effect of processing sorghum silage (SS) at harvest on dry matter intake and nutrient digestibility of beef cattle. A dual-purpose sorghum (ADV2450IG, Advanta seeds, Irving, TX) was harvested (Claas Jaguar 930, Harsewinkel, Germany) at the late-dough stage of grain maturity and processed (PRO) or not (NPR) with a specific SS cracker (196 mm rolls of 125 teeth each, 40% speed differential, 1.1 mm roll gap). Whole-plant was chopped at 15 mm and ensiled in polyethylene ag-bags (60 m long and 2.74 m diameter) for 60 d until the beginning of a performance trial which was followed by the digestibility trial. From a performance trial with eight heifers/pen and 12 pens total (six per treatment), one heifer (13 ± 1.5 mo and 251,4 ± 36.3 kg of BW) by pen was randomly selected for the digestibility trial. Two backgrounding diets containing (DM basis), 90.5% SS either PRO or NPR, 6.5% soybean meal (expeller) and 3% supplement (ROC90, Provimi, Argentina); continued to be offered ad libitum for an extra 3 d of adaptation, while feed and feces were collected the next 4 d. Feed was individually offered once daily, and orts were collected the following day. Fecal samples were collected twice daily and apparent total tract digestibility was determined using uNDF240h as a marker. Data were analyzed as a completely randomized design using pen as the experimental unit, and initial BW as a covariate. Dry matter (DM) and organic matter (OM) intake tended (P>0.07) to be greater, while starch intake was greater (P<0.03) for the NPR treatment. intake of NDF, ADF and CP were not affected by treatments. No differences (P>0.10) were detected for DM, OM, NDF, ADF and CP digestibility, while starch digestibility was greater (P<0.001) by processing (93.55 vs. 86.48 for PRO and NPR, respectively). In conclusion, processing sorghum silage at harvest increased apparent total tract digestibility of starch when SS was fed to backgrounding beef heifers.