308 - Effects of Roughage Source on Growth Performance, Carcass Characteristics, and Rumination Time of Beef Steers Fed Steam-flaked Corn Finishing Diets

We hypothesized that roughage source would not impact rumination time and growth performance if the different sources provided a similar concentration of dietary neutral detergent fiber (NDF) and physically effective NDF (peNDF). This experiment's objective was to evaluate rumination time, and growth performance steers consuming finishing diets with differing roughage sources (corn stalks, cotton burrs, or wheat silage). Beef steers (n = 49; BW = 317 + 5.6 kg) were used in a completely randomized design with 3 dietary treatments. Steers consumed a steam-flaked corn-based diet containing corn stalks (CS), cotton burrs (CB), or wheat silage (WS) included at 7% (DM basis). Dietary NDF was similar (P = 0.36) across treatments. Each steer was fitted with a sensory collar to record daily rumination. Weekly ingredient and dietary samples were estimated for physically effective NDF (epeNDF) using the Penn State Particle Separator. Actual physically effective NDF (apeNDF) was calculated based upon rumination time. Neither initial nor final body weight (BW) differed between treatments (P ­> 0.52); nor did average daily gain (ADG), dry matter intake or carcass adjusted variables of FBW, ADG, empty BW, or empty body fat (P > 0.31). However, gain to feed (G:F) tended to differ (P = 0.06) between treatments. The CS diet had the greatest G:F with no difference (P = 0.75) between CB and WS. Dietary NDF and epeNDF were similar (P > 0.35) among roughage sources; however, CB had the least apeNDF, consistent with lower rumination time (P < 0.01). When energy values were calculated from animal performance, the CS diet had the greatest observed energy values, followed by WS and CB having the least. These results indicate roughage source impacted rumination time, although steers were fed a steam-flaked corn-based finishing diet with similar dietary roughage and NDF inclusions.