EVALUATION OF 4 INTERMEDIATE WHEATGRASS POPULATIONS UNDER GRAZING

The grazing season in the central and northern Great Plains could be e xtended by use of adapted cool-season grass pastures for spring and fa ll grazing to augment the native warm-season range. A grazing trial wa s conducted to evaluate the forage quality of four intermediate wheatg rass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations f or use in forage-livestock systems. The cultivars Slate and Oahe and t wo populations selected for improved IVDMD, 'Manska' and NE TI 1, were evaluated, Each population was seeded in the fall of 1987 in three re plicated 0.4-ha pastures arranged in a randomized complete block desig n, Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha(-1). Duration of grazing was shorter in 1989 because of inadequate soil moisture, Average daily gain (ADG) and gain per hectare were high er (P less than or equal to 0.10) in 1989 than 1990, despite the lower (P less than or equal to 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d(-1), compared with 1.42, 1.27, and 1.43 for Oahe, Slate, and NE TI 1 , respectively, There were no differences (P > 0.10) in ADG or gain pe r hectare among populations in 1990. The improvement in ADG resulted i n 30 to 65 kg more gain per hectare from Manska compared with the othe r populations in 1989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance.