105 The Effects of Roughage Neutral Detergent Fiber Concentration and Bulk Density of Steam-Flaked Corn on Performance, Carcass Characteristics, and Liver Abscesses in Finishing Beef Steers

Abstract We evaluated the effects of dietary neutral detergent fiber (NDF) concentration from alfalfa hay and bulk density of steam-flaked corn (SFC) on growth performance, carcass characteristics, and liver abscesses in finishing beef steers. Crossbred beef steers (n = 214; 60 pens; 10 pens/treatment; initial BW 417 ± 11.9 kg) were blocked by BW and assigned randomly to treatments and fed an average of 112 d. The treatments were arranged as a 2 × 3 factorial and consisted of three NDF concentrations from alfalfa hay (3, 4.5, or 6%) and 335 g/L (10.9 kg/bu) or 425 g/L (14.5 kg/bu) steam-flaked corn (SFC; 33 or 69% starch availability, respectively). Steers were harvested at a commercial abattoir where carcass data and livers scores were collected. Performance and carcass data were analyzed with PROC MIXED of SAS with pen as the experimental unit. Pen quality grade distribution and liver scores were analyzed as binomial proportions using PROC GLIMMIX. No interactions between roughage NDF and bulk density of SFC were noted (P > 0.18); therefore, main effects are presented. Live and carcass-adjusted growth performance did not differ throughout the study (P ≥ 0.28), except for an increase in dry matter intake by steers fed 6% vs. 3 or 4.5% roughage NDF from d 70 to 105 (P = 0.02). Marbling score was greater (P = 0.05) for steers fed 3% than for 4.5 or 6% roughage NDF, and steers fed 335 g/L SFC tended to have a larger longissimus muscle area (P = 0.10) than those fed 425 g/L SFC. Presence of LA at harvest was 17.9 and 23.4% less (P < 0.01) in the steers fed 4.5 and 6% roughage NDF, respectively, than for those fed 3% roughage NDF. Similarly, the presence of A+ abscesses was greater (P = 0.03) in steers fed 3% roughage NDF than in those fed 4.5 or 6% roughage NDF. Liver abscesses were 11.7% less (P = 0.05) in steers fed 425 vs. 335 g/L SFC. Results suggest that increasing roughage NDF and bulk density of SFC are dietary strategies to decrease the presence of liver abscesses at harvest without negatively affecting growth performance.