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 among barley (Hordeum vulgare L.) cultivars due to year grown, head morphology, growth habit and intended end use. Two trials were conducted to identify causal factors for variability among barley cultivars in animal performance, 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 blocks, eight to a pen, in a randomized complete block design and pens to treatments. Steers were fed a diet of 83% steam-rolled barley (Andre, Camelot, Clark, Cougbar, Harrington or Steptoe for 123 d in Trial 1; Boyer, Camelot, Clark, 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 significantly lower than Clark. Digestibility of other nutrients tended to be lowest 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 correlated (r = 0.69; P < 0.0001). Lower nutrient utilization by steers fed Cougbar resulted in lower performance. In Trial 2, steers fed Hesk had a poorer (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, data from these trials suggest that Cougbar and Steptoe are of lower nutritional value than other cultivars under the conditions of these studies. In these studies, digestibility of NDF was a major factor contributing to differences among cultivars.