PSIX-7 - Sorghum Silage: Effects of Processing on Performance of Backgrounding Beef Cattle

Abstract: The aim of the experiment was to evaluate the effect of processing sorghum silage (SS) at harvest, on ADG, DMI and FE of beef heifers. We used 96 Angus heifers in a completely randomized design with 6 pens of 8 heifers per treatment. Mixed model of SAS was used, and the model included the fixed effect of treatment [SS processed (PRO) or not (NPR)] with initial BW used as covariate. Significance was declared at P< 0.05. A dual-purpose sorghum (ADV2450IG, Advanta seeds, Irving, TX) was harvested (Claas Jaguar 930, Harsewinkel, Germany) at the late drought stage of grain maturity and PRO or NPR were obtained with a specific SS cracker (196 mm rolls of 125 teeth each, 40% speed differential, 1.1 mm roll gap). Each treatment was chopped at 15 mm theoretical length of cut and ensiled in polyethylene ag-bags (60 m long and 2.74 m diameter), for 45 d until starting the feeding trial. Two backgrounding diets containing (DM basis), 91.5% SS PRO or NPR (31.4±1.4% grain content on average), 6.5% soybean meal (expeller) and 3% supplement (ROC90, Provimi, Argentina); were offered for a 15 d of adaptation and 60 d of experimental period. Diets were adjusted daily to score 0.5, using the SDSU 4-point bunk scoring system and samples were taken for analyses (Rock River Laboratories, Argentina). Initial, middle and final BW was measured, while DMI was calculated from differences between DM offered and refused, within each pen. In conclusion, harvesting SS using a sorghum-specific cracker led to a 15 and 21% increase in ADG and FE, respectively, when SS was included in diets fed to backgrounding Angus heifers.