222 Effect of corn stalk inclusion rate on performance and rumination behavior in beef steers
Abstract Coarse roughage, such as corn stalks, in feedlot diets aids in the formation of a fibrous mat within the rumen. The fibrous mat supports rumen health, buffers pH, and reduces acidosis risk in cattle consuming high-concentrate diets. Excess roughage can increase physical fill, thus lowering the animal’s ability to consume enough energy for efficient growth. The objective of this experiment was to quantify feedlot growth performance, rumination, ruminal pH and carcass quality and yield outcomes of cattle consuming a finishing diet with increasing levels of roughage. Fifty-one steers (initial BW = 295 + 11 kg) were randomly allocated to 1 of 3 dietary treatments; 5% (5CS; n = 18), 10% (10CS; n = 17), or 15% (15CS; n = 16) corn stalks (DM basis) in a steam-flaked-corn based finishing diet. Steers were fitted with a sensory collar that recorded rumination (min/d) and one-half of the steers (n = 27) received a rumen bolus that continuously monitored pH. The experiment was conducted using a randomized complete block design. Data were analyzed using a mixed model; treatment was a fixed effect and block was a random effect. As CS inclusion increased, we observed increased DM intake (P = 0.01; 7.7, 8.2, and 8.5 kg/d, respectively), decreased gain efficiency (P < 0.01; 0.18, 0.16, and 0.14 kg/kg DM, respectively), and a tendency for decreased ADG (P = 0.09; 1.34, 1.33, and 1.22 kg/d, respectively). Ruminal pH was highest (P < 0.01) for 15CS (6.28) and similar for 5CS and 10CS (6.10). Steers spent more time ruminating (P < 0.01) when consuming the 10CS diet (361 min/d) and least with 5CS diet (279 min/d). Increasing CS to 15% decreased rib fat thickness (P = 0.01), decreased calculated YG (P = 0.02), and decreased marbling score (P < 0.01) compared with the 5CS and 10CS treatments. Feeding excess corn stalks (≥ 15%) may prevent adequate energy intake, thus diminishing feedlot growth performance and carcass merit.