SEASONAL PREFERENCES OF STEERS FOR PROMINENT NORTHERN GREAT-BASIN GRASSES

The objective of this research was to determine, on a seasonal basis, the relative preferences of cattle for 7 native grasses and crested wh eatgrass (Agropyron desertorum (Fischer ex Link)Schultes), a long-used introduction in the Pacific Northwest, Methods involved observing for age selection processes of 3 steers in paddocks, where plants existed in equal densities and in rangeland pastures with variable forage comp osition. Design of paddock and pasture studies was a randomized-comple te-block with 3 replications, 3 stages of phenology (vegetative, anthe sis, and quiescent), and 8-11 forages. Dietary proportions as indexed by bite-counts changed (P < 0.01) with phenology and varied among spec ies. Diets were more similar (P < 0.05) than forage composition betwee n the 2 study areas (paddocks and native pastures), and became less si milar (p < 0.05) as phenology of the grasses advanced from vegetative growth through anthesis and quiescence. Steers were selective grazers during vegetative and anthesis stages of phenology, and despite variat ions in herbage availability, 'Nordan' crested wheatgrass was the most prominent dietary component in paddocks and pastures. Variation in pr oportions of grasses in the diet was associated (P < 0.05) with measur es of available forage in the paddocks (r = 0.46-0.89, (x) over bar = 0.72) but poorly associated with herbage composition in pastures (r = 0.41-0.02, (x) over bar = 0.12). Inconsistencies in rankings of relati ve preference indices and dietary proportions of grasses suggested tha t measures of herbage availability may confound the predictive utility of relative preference indites. More grasses were acceptable to cattl e at quiescence, with crested wheatgrass ranging from 8-26% of the die t. We suggest that with proper management, interseedings of crested wh eatgrass on native range may be used to lessen grazing demands previou sly borne by native perennials early in the grazing season.