Relationship Between Quality Characteristics of Barley Grain and Digestibility in Feedlot Steers

Abstract

Two hundred forty-nine samples of barley grain representing varieties from 13 growing locations were obtained to evaluate variability in nutritive value and to characterize the relationship between chemical composition and digestibility. Ranges for barley NDF, ADF, starch, bulk density (BD), and in vitro total digestibility (IVTD) were 11.8 to 25.6%, 2.2 to 8.8%, 48.2 to 72.5%, 569 to 784 g/L (44 to 61 lb/bu), and 66.7 to 85.1%, respectively. In vitro total digestibility was most closely related to NDF (r =−0.69,P < 0.001); this relationship improved when correlation was determined by variety (r =−0.81;P < 0.001) and location (r =−0.93,P < 0.001). Thirty-two steers were then adapted to a diet consisting of 80% dry-rolled barley (DM basis) from 1 of 8 divergent sources. Steers were assigned randomly to the 8 dietary treatments and in vivo digestibility was measured during 3 experiments replicated over time. Digestibility of DM, OM, and starch were not different between barley sources. Using least squares means for laboratory measures of the 8 sources of barley, NDF was negatively correlated with starch (r =−0.83,P < 0.05) and IVTD (r =−0.87;P < 0.05). Starch was positively correlated with BD and IVTD (r = 0.71 and 0.83, respectively;P < 0.05), and BD was positively correlated with IVTD (r = 0.83;P < 0.05). None of the laboratory variables measured in this study was an adequate predictor of barley digestibility from the digestive tract of feedlot steers.