Browsing Rangeland Ecology & Management, Volume 60, Number 1 (January 2007) by Subjects
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Diet Composition of Cattle Grazing Sandhills Range During SpringThe grazing season on upland Sandhills range traditionally begins in mid-May when the dominant warm-season grasses have initiated growth. Initiating grazing earlier would improve efficiency of use of cool-season plants and reduce the time period during which hay is fed. A 2-year study was conducted to determine nutrient and botanical composition of cattle diets when grazing upland Sandhills range during spring. Diets were collected from esophageally-fistulated cows on 10 April, 1 May, and 22 May each year. Concurrently, current-year, and residual herbage was clipped to determine pasture composition and calculate preference indices for the primary plant species and groups. Averaged across dates, needleandthread (Stipa comata Trin. Rupr.), bluegrasses (Poa spp.), and sedges (Carex spp.) accounted for 19% of the total herbage and 68% of the current-year herbage yield. These species constituted an average of 74% of cow diets. Diet composition of sedges was less on 10 April than on 22 May (P < 0.05), whereas similar amounts of needleandthread and bluegrasses were present on all dates. Preference indices indicated strong selection for species with abundant current-year growth and avoidance of residual herbage. Crude protein content of diets was less on 10 April (10.7%) than on 1 May or 22 May (13.9%, P < 0.05), likely because of a greater amount of residual herbage present in 10 April diets. Overall quality of diets would meet requirements of average spring-calving cows; however, grazing management strategies would need to account for the limited availability of current-year growth during spring, particularly April, to ensure that cattle are meeting their nutrient needs.
Livestock Forage Conditioning Among Six Northern Great Basin GrassesStudies of Anderson and Scherzinger’s forage conditioning hypothesis have generated varied results. Our objectives were: 1) to evaluate late summer/early fall forage quality of crested wheatgrass (Agropyron desertorum [Fisch. ex Link] J. A. Schultes), bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve), Idaho fescue (Festuca idahoensis Elmer), bottlebrush squirreltail (Elymus elymoides [Raf.] Swezey), Thurber’s needlegrass (Achnatherum thurberianum [Piper] Barkworth), and basin wildrye (Leymus cinereus [Scribn. Merr.] A. Löve) from ungrazed paddocks and paddocks grazed at vegetative, boot, and anthesis; and 2) test hypotheses that postgrazing regrowth yields were correlated with soil moisture content when grazing occurred. Crop-year precipitation for 1997 and 1998 was 134% and 205% of average. Crude protein (CP) and in vitro dry matter digestibility (IVDMD) of ungrazed grasses displayed expected declines in quality. Among ungrazed grasses, late summer/ early fall CP was 5.7% in 1997 and 3.6% in 1998; IVDMD was 47% and 41%, respectively. Late summer/early fall forage quality was elevated by vegetative, boot stage, or anthesis grazing. The phenologically youngest regrowth always ranked highest in CP and IVDMD. Among grasses, respective 1997 CP and IVDMD means were 9.0% and 55% for regrowth following anthesis grazing. No regrowth followed anthesis grazing in 1998, but CP and IVDMD means from boot stage treatments were 5.5% and 47%, respectively. With CP measures, a species by treatment interaction occurred in 1997, but species reacted similarly in 1998. Vegetative, boot stage, and anthesis grazing in 1997 caused respective late summer/early fall standing crop reductions of 34%, 42%, and 58%; and 34%, 54%, and 100% reductions in 1998. Forage conditioning responses were lower for bluebunch wheatgrass and crested wheatgrass than other grasses. Soil moisture content was a poor predictor of regrowth yields. Managed cattle grazing can successfully enhance late season forage quality.