Submitted to: Texas A&M Research and Extension Center Progress Report
Publication Type: Experiment Station
Publication Acceptance Date: 7/2/2003
Publication Date: 8/1/2003
Citation: Hough, B., Greene, L.W., Mccollum, F.T., Bean, B.W., Cole, N.A., Montgomery, T. 2003. Performance of feedlot heifers fed corn silage or brown midrib forage sorghum silage as the roughage portion of a finishing diet. Texas A&M Research and Extension Center Progress Report. p. 56-58. Interpretive Summary: Corn silage is fed as a roughage in many feedlot-finishing diets. However, production of corn silage requires considerable amounts of irrigation water. Sorghum is more drought tolerant than corn and is more efficient at using water. However, sorghum silage is rarely used in beef cattle finishing diets because of its low digestibility. New brown midrib sorghums are more digestible than forage hybrids currently available, but their value in comparison to corn silage is not known. Therefore, this study was conducted to compare the feeding value of silages made from brown midrib sorghum and corn. One hundred twenty six cross bred heifers (average BW = 315 kg) were used in the experiment and fed finishing diets that contained either 10% corn silage, 10% sorghum silage or 7.5% sorghum silage. Heifers fed the sorghum silage diets gained weight as fast or faster than those fed corn silage and tended to be more efficient. Results indicate that silage made from brown midrib sorghum has a feeding value for finishing beef cattle similar to that for corn silage. Results of this trial suggest that if feedyards switch from using corn silage to using sorghum silage, use of irrigation water can be significantly decreased without adversely affecting animal performance.
Technical Abstract: One hundred twenty six cross bred heifers (average BW = 315 kg) were used to determine the performance of heifers fed brown midrib forage sorghum silage (BMRS) vs. corn silage (CS) as the roughage source in a finishing diet. Silage was stored in 4.5 m diameter silage bags. Heifers were randomly assigned to one of three diets, 10% (DM basis) CS (C10), 10% (DM basis) BMRS (S10), and 7.5% (DM basis) BMRS (S7.5) in a randomized block design. Other diet ingredients consisted of steam flaked corn, fat, and supplement. Diets were formulated to include CS and BMRS at equal levels of DM inclusion (C10 vs. S10), and equal NDF concentrations (C10 vs. S7.5). Heifers were housed in 18 pens (7/pen), and fed in fence-line bunks. Carcass characteristics were determined after harvest. Heifers fed either the S10 or S7.5 diets gained 11.3% faster (P < 0.03) than those fed C10 (1.38 and 1.38 vs. 1.24 kg/d, respectively). Feed intake (8.5, 8.8, and 8.7 kg/d for C10, S10 and S7.5 respectively) was not different (P = 0.43) across treatments. Gain efficiency (gain/intake) was greater (P < 0.01) for heifers fed S10 and S7.5 than those fed C10 (0.158 and 0.158 vs. 0.148, respectively). Heifer performance was not different (P > 0.10) for heifers fed S10 vs. S7.5. No differences in carcass characteristics were detected (P > 0.10). Due to storage of the silages, the CS contained noticeable mold on the face of the silage when feeding, which may have affected subsequent heifer performance. Results indicate that BMRS as a roughage source will not affect performance of heifers fed a high concentrate finishing diet when compared to those fed CS.