|Cruz, Ruben - OREGON STATE UNIVERSITY|
Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 3, 1997
Publication Date: N/A
Interpretive Summary: There is little information on the preferences of cattle for most Pacific Northwest and Great Basin rangeland grasses. This information is needed to plan year-round gazing programs and assess grazing effects on rangelands. A study was conducted to see which grasses cattle liked at 3 stages of growth: 1)when plants were leafy, 2)when seedheads had emerged and were flowering, and 3)when grasses had stopped growing and turned brown. Grasses were: bluebunch wheatgrass, Idaho fescue, squirreltail, needle-and-thread, Sandberg's bluegrass, Thurber's needlegrass, giant wildrye, and crested wheatgrass. The preferences of the cattle changed as the growing season advanced. When grasses were leafy or flowering, crested wheatgrass was preferred and cattle avoided Sandberg's bluegrass, Idaho fescue, needle-and-thread, and Thurber's needlegrass. Bluebunch wheatgrass and giant wildrye were acceptable. When grasses had cured and turned brown, cattle preferred giant wildrye, rejected crested wheatgrass and needle-and-thread, and accepted the other 5 species. When it is green, crested wheatgrass is the forage of choice for cattle in spring and early summer, and the other grasses are favored in late summer after forages turn brown. A mix of crested wheatgrass and native grass pastures can assure acceptable forages are available to cattle on a year-round basis.
Technical Abstract: The objective of this research was to determine, on a seasonal basis, the relative preferences of cattle for 7 native grasses and crested wheatgrass. Dietary proportions as indexed by bite-counts changed (P<0.01) with phenology and varied among species. Pasture paddock comparisons of steer diets and available herbage with Kulczynski's similarity indices showed diets were more similar (P<0.05) than forage composition between the 2 areas, and that diets became less similar (P<0.05) as phenology of the grasses advance from vegetative growth through anthesis and quiescence. Steers were selective grazers during vegetative and anthesis stages of phenology, and despite variation in herbage availability, 'Nordan' crested wheatgrass was the most prominent dietary component in paddocks and pastures. Variation in proportions of grasses in the diet was correlated (P<0.05) with measures of available forage in the paddocks (r=0.46-0.89, mean=0.72) but poorly related to herbage composition in pastures (r=0.41-0.02, mean=0.12). More grasses were acceptable to cattle at quiescence, with crested wheatgrass being only 8-26% of the diet. We suggest that with proper management, interseedings of crested wheatgrass on native range may be used to lessen grazing demands previously born by native perennials early in the grazing season.