BARLEY VARIETIES FOR FINISHING STEERS .2. RUMINAL CHARACTERISTICS ANDRATE, SITE, AND EXTENT OF DIGESTION

Four ruminally and abomasally cannulated steers were used to evaluate the effects of barley variety on rate, site, and extent of digestion o f high-concentrate diets. The treatments compared were 1) corn, 2) Gun hilde barley (GUN), Harrington barley (HAR), and 4) Medallion barley ( MED). Diets were balanced to be isocaloric and isonitrogenous. Ruminal OM digestion was greater(P =.04) in steers fed corn than in those fed GUN, HAR, and MED (61.9 vs average 53.7%). No differences (P >.10) we re seen in ruminal starch digestion (average 92.8%) or in starch flow to the abomasum (average 199 g/d) between diets. Total tract digestion of starch was greater (P =.09) in steers fed barley than in those fed corn (average 98.6 vs 95.7%). Total and nonammonia N presented to the abomasum were greater (P <.05) for steers fed HAR and GUN than for th ose fed MED and corn. Microbial N flow was lowest(P =.01) in corn-fed steers, highest in steers fed GUN and HAR, and intermediate in steers fed MED. Microbial efficiency was 59% greater (P =.03) in steers fed b arley than in steers consuming corn. Ruminal acetate: propionate was l ower (P =.002) in steers fed corn and HAR than in those fed GUN and ME D. Compared to GUN, HAR, and MED barleys, corn had a lower (P <.03) ra te (-.11 vs average -.47) and extent (15 h; 70.3 vs average 98.1%) of in situ starch disappearance. Differences in digestive characteristics found between barley varieties may contribute to differences in anima l performance.