Variation in chemical composition and nutritional quality among barley cultivars for ruminants. 2. Digestion, ruminal characteristics and in situ disappearance kinetics

Two trials were conducted to compare the effects of feeding six different b arley (Hordeum vulgare L.) cultivars on diet digestibility, DE content, and ruminal fermentation characteristics. In Trial 1, four steers (455 +/- 1.6 kg) were used in a partially balanced incomplete block design and consumed a diet of 83% barley (Andre, Camelot, Clark, Cougbar, Harrington or Stepto e), 10% bromegrass hay and 7% supplement. Organic matter intake was lower ( P < 0.10) for steers fed Clark, and in situ rate of disappearance of Stepto e was slower (P < 0.10) than other barleys. Acetate to propionate ratio was lower (P < 0.10) in ruminal fluid of steers fed Camelot than in that of th ose fed Andre, NDF digestibility was lower (54.7 vs. 69.2%), and digestion of NDF polymeric monosaccarides was lower (P < 0.10) for Camelot than for A ndre. Scanning electron micrographs supported differences observed in chemi cal composition and in situ disappearance kinetics. In Trial 2, six steers (512 +/- 1.8 kg) were used in a 6 x 6 Latin square design and consumed a di et of 83% barley (Boyer, Camelot, Clark, Harrington, Hesk or Steptoe), 10% bromegrass hay and 7% supplement. Steers fed Camelot had greater (P < 0.10) total tract NDF digestibility than steers fed Hesk and Steptoe. Total poly meric monosaccharide digestion was lower (P < 0.10) fbr Boyer (62.9%) than for any of the other cultivars (73.5%, average) except Hesk. In these two t rials, NDF and NDF polymeric monosaccharide digestibilities were the major factors contributing to variability among barley cultivars in nutritional q uality for ruminants.