Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2009
Publication Date: 3/1/2010
Citation: Hales, K.E., McMeniman, J.P., Leibovich, J., Vasconcelos, J.T., Quinn, M.J., May, M.L., Dilorenzo, N., Smith, D.R., Galyean, M.L. 2010. Effects of varying bulk densities of steam-flaked corn and dietary roughage concentration on in vitro fermentation, performance, carcass quality, and acid-base balance measurements in finishing steers. Journal of Animal Science. 88:1135-1147. Interpretive Summary: The use of processed grains is standard in the cattle feeding industry. Corn is commonly processed to increase the starch availability which improves cattle performance and gain efficiency. As grain processing increases, bulk density or bushel weight (lb/bu) of steam-flaked corn (SFC) decreases. Including small amounts of roughage such as hay in processed grain diets can prevent digestive upsets and maximize energy intake by feedlot cattle. Thus, grain processing and dietary roughage concentration are major factors affecting performance of feedlot cattle. Therefore, we conducted three studies to evaluate the interaction of bulk density of SFC and dietary roughage concentration on performance and carcass measurements in feedlot cattle. In Experiment 1, four diets were fed in which SFC was the principal energy source. The diets contained SFC processed to two densities [low (26 lb/bu) or high (30 lb/bu)] and 6 or 10% alfalfa hay. Cattle fed the lower bulk density of SFC had greater gain efficiency than those fed the higher bulk density of SFC, and feeding 6% roughage improved overall gain efficiency. In Experiment 2, the effects of bulk density of SFC (22, 26, or 30 lb/bu) and 6 or 10% alfalfa hay on in vitro dry matter disappearance and in vitro pH were evaluated. In vitro pH increased with increasing bulk density, which would likely relate to increased digestibility. In Experiment 3, two diets that varied in bulk density of SFC and roughage concentration (26 lb/bu SFC with 6% roughage vs. 30 lb/bu SFC with 10% roughage) were compared for effects on pattern of feed intake and acid-base balance in Holstein steers. No treatment effects were observed for the acid-base balance parameters, and the two treatments had little effect on pattern of feed intake. Our data from the three experiments suggests that within the ranges of bulk density and roughage level studied, 26 lb/bu SFC with 6% roughage yielded optimal animal performance with limited effects on in vitro fermentation and acid-base balance.
Technical Abstract: Effects of varying bulk densities of steam-flaked corn (SFC) and level of inclusion of roughage in feedlot diets were evaluated in three experiments. In Experiment 1, 128 beef steers were used in a 2 x 2 factorial arrangement to evaluate effects of bulk density of SFC (335 or 386 g/L) and roughage concentration (6 or 10% ground alfalfa hay; DM basis) on performance and carcass characteristics. No interactions were observed between bulk density and roughage concentration for performance data. From d 0 to end, cattle fed the 335 g/L SFC had greater overall G:F (P = 0.04) than those fed 386 g/L SFC, with tendencies (P < 0.10) for improved G:F with the lower flake weight evident at all 35-d intervals throughout the feeding period. Dry matter intake was less by cattle fed 6 vs. 10% roughage from d 0 to 35 (P = 0.03) and d 0 to 70 (P = 0.05), but not for the overall feeding period. Feeding 6% vs. 10% ground alfalfa as the roughage source tended (P = 0.09) to improve overall G:F. Treatment effects on carcass measurements were generally not significant. In Experiment 2, effects of bulk density of SFC (283, 335, or 386 g/L) and 6% or 10% ground alfalfa hay on in vitro dry matter disappearance (IVDMD) and in vitro pH were evaluated at 6, 12, 18, and 24 h of incubation. With a reduced-strength buffer in vitro fermentation system, pH increased (P < 0.01) with increasing bulk density at 6 and 12 h, and IVDMD decreased (P < 0.03) as bulk density increased. In contrast, in a normal-strength buffer system, there were no treatment differences for IVDMD. In Experiment 3, two diets that varied in bulk density of SFC and roughage concentration (335g/L SFC with 6% alfalfa hay vs. 386 g/L SFC with 10% alfalfa hay) were compared for effects on pattern of feed intake and acid-base balance in Holstein steers (12/treatment). No differences between treatments were noted for blood gases or urine pH; however, day effects (P < 0.02) were detected for blood pH, partial pressure of CO2, and urine pH, which generally decreased (P < 0.05) with increasing time on feed. The two treatments had little effect on pattern of feed intake within sampling days, with the exception that the 386 g/L SFC-10% alfalfa hay diet increased (P < 0.05) percentage of total DMI consumed at 1 and 6 h after feeding on d 14. Within the ranges of bulk density and roughage level studied, 335 g/L SFC with 6% alfalfa hay yielded optimal animal performance with limited effects on in vitro fermentation and acid-base balance.