Variation in chemical composition and nutritional quality among barley cultivars for ruminants. 1. Steer finishing performance, diet digestibilities and carcass characteristics

Inherent variability in chemical composition and nutritional value exists a mong barley (Hordeum vulgare L.) cultivars due to year grown, head morpholo gy, growth habit and intended end use. Two trials were conducted to identif y causal factors for variability among barley cultivars in animal performan ce, carcass characteristics, diet digestibility and digestible energy (DE) content. In feedlot trials, 144 large-frame beef steers (380 +/- 1.6 kg in Trial 1, 372 +/- 0.8 kg in Trial 2) were assigned within three weight block s, eight to a pen, in a randomized complete block design and pens to treatm ents. Steers were fed a diet of 83% steam-rolled barley (Andre, Camelot, Cl ark, Cougbar, Harrington or Steptoe for 123 d in Trial 1; Boyer, Camelot, C lark, Harrington, Hesk or Steptoe for 119 d in Trial 2), 10% silage (wheat in Trial 1, oat in Trial 2), and 7% supplement on a dry matter (DM) basis. In Trial I, Cougbar neutral detergent fiber (NDF) digestibility was signifi cantly lower than Clark. Digestibility of other nutrients tended to be lowe st for steers fed Cougbar and as a result, diet DE was lower (P < 0.05) for Cougbar than for Clark and Camelot. Diet DE and NDF digestibility were cor related (r = 0.69; P < 0.0001). Lower nutrient utilization by steers fed Co ugbar resulted in lower performance. In Trial 2, steers fed Hesk had a poor er (P < 0.05) ratio of feed to gain than steers fed Camelot and Harrington and lower (:P < 0.05) digestibility than steers fed Steptoe. In summary, da ta from these trials suggest that Cougbar and Steptoe are of lower nutritio nal value than other cultivars under the conditions of these studies. In th ese studies, digestibility of NDF was a major factor contributing to differ ences among cultivars.