EFFECT OF BARLEY VARIETY AND DIETARY BARLEY CONTENT ON DIGESTIVE FUNCTION IN BEEF STEERS FED GRASS HAY-BASED DIETS

Five ruminally and duodenally cannulated steers were used in a 5 x 5 L atin square design with a 2 x 2 + 1 arrangement of treatments to study the effects of barley variety and dietary barley content on digestive function in steers fed grass hay-based diets. Barley varities evaluat ed were Russell and Steptoe, which had bulk densities of 67.7 and 64.5 kg/hL, respectively. Supplemental treatments were as follows: corn, l ow Russell(Ru-lo), low Steptoe (St-lo), high Russell (Ru-hi), and high Steptoe (St-hi). Corn, Ru-lo, and St-lo were provided at 30% (DM basi s) of grass hay-based diets, whereas Ru-hi and St-hi were provided at 35.5% of diet DM (equal starch content as the corn treatment). No trea tment differences (P > .10) were observed for DMI, ruminal particulate passage rate, and NDF total tract digestibility. Ruminal DM and starc h digestibility were greater (P <.01) for barley-containing diets than for the corn diet. Similarly, total tract DM(P <.10) and starch(P <.0 1) digestibility was greater for barley than for corn diets. Microbial protein and non-NH3 N flow to the small intestine were greater (P <.0 1) for the barley diets than for the corn diet. Starch intake (P <.01) and DM digestibility (P <.10) were greater for high-than for low-barl ey diets; however, differences due to barley variety were not observed (P >.10). In situ disappearance of grass hay NDF at 8 and 96 h of inc ubation was greater (P <.05) for barley than for corn diets. Rate of i n situ disappearance of grain DM was greater (P <.01) for barley than for corn and for Russell than for Steptoe barley. Responses suggest th at-ruminal and total tract digestibility and protein flow to the small intestine can be increased with barley compared with corn as an energ y supplement to grass hay-based diets.