In the semi-arid Northern Great Plains, seeded cool-season grasses are primarily recommended for spring and fall grazing because their nutritive quality is perceived as too low to support acceptable animal weight gains during mid-summer. This perception is caused in part by traditional use of high spring stocking rates, which leave little forage remaining for mid-summer use. A study was conducted near Mandan, N.D. to determine the effect of moderate (1.6 AUM ha(-1)) and heavy (2.4 AUM ha(-1)) stocking rates on weight gains of yearling Hereford steers grazing crested wheatgrass (Agropyron desertorum [Fisch. Ex Link] Schult.), western wheatgrass (Pascopyrum smithii [Rydb.] Love), smooth bromegrass (Bromus inermis Leyss.) and flat (class II and III) and rolling (class IV and VI) native rangelands. Studies were conducted over a 140-day grazing season during 3 summers from 1992-1994. Grazing was initiated in mid-May and terminated the last week of September or the first week of October each year. At the end of each grazing season forage samples were clipped inside and outside of cages randomly located in each pasture to estimate end of season standing crop and forage utilization. Animal activity data were collected for 9 days during August and September 1994. Steer weight gains were not different among crested wheatgrass, western wheatgrass, smooth bromegrass and flat native pastures, but weight gains of steers grazing rolling native pastures were lower (P < 0.05) than gains on other pastures. Weight gains per steer were 8% higher (P < 0.05) on moderately grazed pastures, but weight gains per hectare were 39% higher on heavy grazed pastures. Steers spent more (P < 0.05) time grazing on smooth bromegrass than western wheatgrass, crested wheatgrass, or flat native pastures and they also spent more (P < 0.05) time grazing on heavy than moderately grazed pastures. Seeded cool-season grasses produced season-long yearling steer weight gains comparable to flat native, and superior to rolling native pastures, even when grazed at a stocking rate that was 80% heavier than the rate recommended for native rangeland by the USDA-SCS (1984). These results suggest that seeded cool-season grasses can be successfully grazed season-long in the Northern Great Plains where environmental conditions and precipitation patterns are comparable to central North Dakota.

Field studies were conducted in 2 types of grasslands in the Pryor Mountain Wild Horse Range of northern Wyoming and southern Montana to examine plant biomass production and nitrogen responses to the separate and combined effects of graminoid defoliation and increased environmental resource (water or nutrients) supply. Short-term plant responses were monitored over 2 years which differed substantially in growing season precipitation. In the arid, low elevation grassland, total grass biomass was significantly lower in the dry year than the wet year in all treatments. Defoliation of the grasses did not reduce their aboveground biomass production in the wet year, but severely reduced it in the dry year, primarily because of a decrease in tiller density. Mass of remaining individual tillers increased with clipping in the dry year, and nitrogen concentrations of the grasses increased with clipping in both years. Irrigation alone increased total belowground biomass compared to the other treatments, but did not increase the aboveground biomass production of any plant functional group. Clipping plus irrigation resulted in greater total aboveground biomass production and higher nitrogen concentrations of the grasses than control or irrigated treatments. Clipping graminoids in the more mesic montane grassland did not decrease their biomass production in either year, but did increase their nitrogen concentrations and increase the collective aboveground biomass production of the other plant functional groups. Fertilization and fertilization plus clipping significantly increased total aboveground biomass production in both years, and total belowground biomass was greatest in fertilized plots.

Competition for milk between calves and pastoral herders may reduce weaning weights, retard growth, and delay puberty in cattle. Calf supplementation could over-ride such effects and improve pastoral economies. To examine these issues in semiarid Ethiopia, 266 Boran calves (Bos indicus) were used in a 2 X 3 plus 1 factorial design contrasting graded levels of supplemental alfalfa hay (i.e., Medicago sativa L. with mean intakes of 0, 344, and 557 g head(-1) day(-1) on a DM basis) and supplemental water (i.e., with mean intakes of 0 and 3.8 liters head(-1) day(-1)). The trial was repeated for animals born in 2 consecutive years. Treatments occurred over a background of simulated traditional management in which calves had limited access to grazing and water and were allowed to suckle about two-thirds of their dams' daily milk yield. Traditionally managed controls received no supplements while other (positive) controls received no supplements but had greater access to milk. After 10 months of treatment calves were weaned and monitored. Supplementation with the high level of hay plus water markedly enhanced (P < 0.01) all productive features of calves at weaning compared to traditionally managed controls, and was an effective substitute for milk forgone in both years. Despite high variability in milk intake, access to supplements, and weaned body size as calves, all male cattle converged in liveweight and other productive features by 3.5 years of age, largely due to compensatory growth of traditionally managed controls. Heifers also converged in various attributes at maturity, but those which had received hay plus extra water as calves still conceived 2.6 to 4.3 months earlier (P < 0.05) than traditionally managed controls. We concluded that supplementation with hay and water can indeed compensate a young calf for typical levels of milk restriction here. Carry-over effects, however, were insufficient to justify large investments in supplementation considering the high inherent risks of production and traditions of marketing mature animals.

Combined with other information, fecal output appears to have potential use in models to predict forage intake. Better understanding of fecal output dynamics relative to forage availability could improve model estimates of animal performance. Field trials were conducted during 4 different periods to investigate the relationship between 1) declining forage mass or forage component availability and beef steer fecal output and between 2) browse consumption and available forage mass. Fecal output was estimated using the rare-earth marker ytterbium. Initial fecal output as a percentage of body weight was greatest in March (1.24%) and least in August (0.96%). Regression slopes were negatively correlated (-0.73) with initial forage mass. As indicated by regression slopes, fecal output declined most rapidly in March (slope = 0.57) and slowest in August (slope = 0.13). Expression of available forage mass as either daily grass allowance or daily grass leaf allowance, both as g dry matter/kg live weight, produced similar regression equation statistics. Development of regressions for individual pastures within trials did, however, improve equation statistics in all trials except August. Browse consumption was < 10% until daily grass allowance fell below 50 g/kg live weight then increased to between 53 and 64% below 25 g/kg live weight, but was not adequate to maintain fecal output. Apparent seasonal differences in fecal output suggest lower forage intake (29%) in August compared to March. Fecal output was not affected by daily grass allowance above 100 g. Fecal output declined to below 0.6% of body weight below 100 g daily grass allowance. Data are interpreted to suggest that different fecal output curves and/or adjustment factors may be needed to account for season and initial forage mass.

Prey selection by mountain lions (Puma concolor) in the Aravaipa-Klondyke area in southeastern Arizona was studied from February 1991 to September 1993. Overall diet as determined from frequency of occurrence in 370 scats was 48% deer (Odocoileus virginianus cousi and O. hemionus combined), 34% cattle, 17% javelina (Tayassu tajacu), 6% rabbit (Sylvilagus spp. and Lepus californicus combined), 4% rodent, and 2% desert bighorn sheep (Ovis canadensis mexicanus). With respect to biomass consumed, cattle composed 44%, deer 40%, javelina 10.9%, rabbits 2.9%, and rodents 0.02%. Based on mean weights of prey consumed, the proportion of individuals killed and eaten changed to rabbits 52.7%, deer 16.3%, rodents 12%. javelina 10%, cattle 8%, and desert bighorn sheep 0.5%. Mountain lions selected deer less frequently than their availability would suggest, selected calves slightly more than their availability, and javelina as expected. We speculated that lions selected calves because they were more vulnerable to predation than deer.

Forage nitrogen (N) and phosphorous (P) concentrations and in-vitro dry-matter digestibility (IVDMD) were measured in 2 important riparian species the year following short-term, high-intensity cattle grazing treatments in a montane riparian ecosystem in northcentral Colorado. Current year's growth of water sedge (Carex aquatilus Wahlenb.) and planeleaf willow (Salix planifolia Pursh.) was collected monthly from May to September 1996. The effects of grazing and season of grazing in 1995 on forage quality the following growing season was determined. Season of grazing (i.e., late-spring, early-summer, late-summer, and fall) the previous year did not differentially affect forage quality in either species. However, grazing by cattle the previous year did increase forage quality of water sedge as compared with plants that were not previously grazed. Grazed water sedge plants had higher concentrations of N and P and greater IVDMD than ungrazed controls. Nitrogen and P concentrations of browsed planeleaf willow were not different from controls, but current year's growth collected in the fall from previously browsed plants was 11% more digestible than current year's growth from non-browsed willow. The 2 species responded uniquely to cattle use, which suggested that these 2 life forms differ in response to herbivory. This study supported the hypothesis that grazing by cattle would improve forage quality in a riparian ecosystem, although results varied with life form.