• Effects of water quality on cattle performance

      Willms, W. D.; Kenzie, O. R.; McAllister, T. A.; Colwell, D.; Veira, D.; Wilmshurst, J. F.; Entz, T.; Olson, M. E. (Society for Range Management, 2002-09-01)
      Water is an important nutrient for livestock production and is often provided on rangelands directly from ponds or dugouts. Cattle may defecate and urinate into the water thereby adding nutrients and reducing palatability. A study was conducted to examine the effects of water source on cattle production and behavior, to determine the relationship of selected chemical and biological constituents on the observed response and to test the effect of fecal contamination on water consumption. Four dugouts or ponds were selected at 4 sites: 2 in the Fescue Prairie near Stavely in southwestern Alberta, 1 in the Mixed Prairie at Onefour in southeastern Alberta, and 1 in the Palouse Prairie near Kamloops, British Columbia. Yearling Herefords were tested at 3 sites and Hereford cow-calf pairs at 1 Stavely site. At each site, three paddocks radiated from the pond that were stocked with 10 yearlings or cow-calf pairs randomly assigned to either clean water (water delivered to a trough from a well, river, or pond), pond water pumped to a trough (pond(trough)), or direct access into the pond (pond(direct)). The trials were repeated at each site for 3 to 6 years. Observations were made on cattle weight gains, cow backfat thickness, and activity budgets. Fecal samples were analyzed for selected parasites and pathogens. Other experiments were conducted to determine the effects of manure-contaminated water on feed and water consumption and water selection. Calves, with cows drinking clean water, gained 9% more (P < 0.10) weight than those with cows on pond(direct) but cow weight and backfat thickness were not affected. Yearling heifers having access to clean water gained 23% (P = 0.045) and 20% (P = 0.076) more weight than those on pond(direct) and pond(trough), respectively. Cattle avoided water that was contaminated with 0.005% fresh manure by weight when given a choice of clean water. Cattle that had access to clean water spent more time grazing and less time resting than those that were offered pond(trough) or pond(direct). Cattle management must consider water quality together with forage conditions in order to achieve optimal production from rangeland.
    • Influence of grazing lease terms on economic optimal stocking rates

      May, G. J.; Jones, R. D.; Langemeier, M. R.; Dhuyvetter, K. C. (Society for Range Management, 2002-09-01)
      The terms of grazing lease contracts potentially influence a tenant's incentive to preserve the vegetation resource. Annual stocking rate decisions dictate the degree of overgrazing, which can be cumulative over long periods of time. The objective of this study was to identify the impact the tenant's lease length and lease type has on profit maximizing stocking rates. A multi-period nonlinear programming model was developed to identify economically optimal stocking rates each year over a 24-year period. The model was solved under 1-, 4-, 8-, and 12-year leases on a "per ha" and "per head" basis. The relative importance of each lease alternative and other input values in explaining the tenant's optimal stocking rate was ranked based on standardized ordinary least squares coefficient estimates. Lease length and lease type had a minor impact on optimal stocking rates relative to non-lease factors such as livestock prices and production costs. Holding lease length constant, per ha leases generated a 2% higher average stocking rate than per head leases. Optimal stocking rates were inversely related to the length of the lease. Twelve-year leases generated 18 and 13% lower optimal stocking rates than the 1-year per ha and per head leases, respectively. The optimal stocking rate difference between an 8-year and a 12-year lease was negligible, suggesting the 8-year lease would provide a similar incentive to protect vegetation as a lease with a longer planning horizon.
    • Free-choice grazing of native range and cool-season grasses

      Karn, J. F.; Ries, R. E. (Society for Range Management, 2002-09-01)
      A grazing system which allows cattle to select a season-long diet more nearly meeting their nutrient requirements should facilitate optimal weight gains. A study was conducted near Mandan, N. D. comparing season-long weight gains of yearling steers free-choice grazing on composite pastures containing equal sized plots of 'Nordan' crested wheatgrass (Agropyron desertorum) (Fisch. Ex. Link) Schult.), 'Rodan' western wheatgrass (Pascopyrum smithii (Rydb.) Löve), 'Lincoln' smooth bromegrass (Bromus inermis Leyss.), and native range, to pastures containing the individual pasture types alone. The study was initiated in mid-May and terminated in early October each year from 1995-1997. Pastures were grazed at a stocking rate of 1.9 ha per steer for 147 days or 1.7 AUM ha(-1). Steer behavior on composite pastures was recorded every 10 min. from dawn to dusk 2 days per week each summer. In 1997, forage samples were clipped for chemical analysis at 4-week intervals from all pasture types either within composite pastures or as individual pasture types. Only in 1996 were daily gains of steers on the free-choice treatment different (P < 0.10) from all other treatments. Over the 3-year study, daily gains for steers on the free-choice treatment (1.11 kg) were statistically equal to steers on smooth bromegrass (1.04 kg) and western wheatgrass (1.00 kg) and were significantly greater than daily gains on native range (0.98 kg) and crested wheatgrass (0.97 kg). Steers tended to spend a greater percentage of observation time grazing smooth bromegrass than the other 3 pasture types, especially early in the grazing season. The period of maximum grazing preference for the other pasture types was late in the season in 1995 and 1996 for crested wheatgrass, in mid-season in 1996 for native range, and late in the season in 1997 for western wheatgrass. Chemical analysis of forage samples collected in 1997 show that smooth bromegrass had the highest crude protein and in vitro dry matter digestibility, and the lowest neutral detergent fiber at all 3 summer grazing periods. Forage quality data and the preference of steers for smooth bromegrass help to explain why steers on this treatment had excellent daily gains, especially during early and mid-season.
    • Sample numbers for microhistological estimation of fecal vizcacha diets

      Bontti, E. E.; Bóo, R. M. (Society for Range Management, 2002-09-01)
      Precise estimates of diet composition are useful to assess herbivores impact on rangelands and to make management decisions. Since the variability within- and between-samples affect precision of estimates on diet studies, we studied this variability in diets of the rodent vizcacha (Lagostomus maximus Blainv.). We analyzed fecal pellets using a microhistological technique and we estimated the number of samples and subsamples required to achieve given confidence levels. Diets of this herbivore, which is thought to compete with cattle for forage, were studied in November 1994, May, July, and October 1995 in a mixed shrub-grassland community of the southern caldénal in central Argentina. Most grasses, the main components of the diets (> 80%), were estimated with high precision (confidence interval: CI = 10%, p = 0.05) by observing 14 samples and 5 slides per sample. Forbs (5-6%) and shrubs (12%) were estimated with this same number of samples and slides, but yielded a lower level of precision (CI = 20%, p = 0.10). Although our results may not be directly applicable to other vegetation or herbivores, the procedures may be used in other situations to improve precision of diet estimates through microhistological analysis of feces.
    • Cattle population dynamics in the southern Ethiopian rangelands, 1980-97

      Desta, S.; Coppock, D. L. (Society for Range Management, 2002-09-01)
      Knowledge of livestock population dynamics is important to better understand functional attributes and development potential of pastoral production systems. With a focus on the Borana system of semi-arid Ethiopia for 1980-97, the main objectives of this research were to: (1) Characterize cattle population trends; (2) determine associations of rainfall and stocking rate with change in cattle numbers; and (3) estimate economic losses from cattle mortality. We predicted that the regional cattle population trend would consist of a "boom and bust" cycle with long periods of gradual herd growth punctuated by drought-induced losses. We expected that cattle losses would occur when high stocking rates were combined with large rainfall deficits. Such observations would refute the idea that cattle numbers were erratic and purely controlled by rainfall variation, as predicted by non-equilibrium theory. Cattle dynamics were quantified using herd histories from interviews of 56 households living in 4 sites. Data were aggregated to portray regional cattle population trends and quantify economic losses. Regression analysis was employed to assess associations of rainfall variation and stocking rate with cattle dynamics using 2 approaches: (1) Regional using aggregate herd data, empirical rainfall records, and calculated estimates for stocking rates; and (2) local using site-specific herd data along with recall of rainfall and stocking rate dynamics. Overall, results confirmed that cattle numbers followed a boom and bust cycle. Average cattle holdings dropped front 92 to 58 head/household between 1980 and 1997, respectively. Droughts in 1983-5 and 1991-3 resulted in the deaths of 37 to 42% of all cattle, respectively, up to 15-times higher than net sales. Over 17 years our target population of 7,000 households lost 700,000 cattle with a capital asset loss valued at USD 45 million. Statistical results were more difficult to interpret. Our regional approach indicated neither rainfall nor stocking rate were significantly associated with cattle mortality. We felt this interpretation was erroneous, however, due to a probable-but unmeasured-decline in key grazing resources that lowered carrying capacity, increased herd instability between successive droughts, and undermined relationships among model parameters. Our local approach was somewhat clearer in that results indicated cattle losses were significantly and consistently associated with rainfall deficits, and occasionally associated with high stocking rates that varied by site. We were concerned, however, about respondent bias and possible error in these results. We concluded that the strongest information we had was simply the aggregate pattern of herd dynamics. When aligned with empirical rainfall records and augmented with data from another dramatic cattle crash in 1998-9, we make the case that stocking rate indeed appears to influence the likelihood that a dry year will reduce cattle numbers. We concluded that the Boran live in a dynamic and productive equilibrial system where land-use change has interacted with rainfall variation to create a vicious cycle of massive cattle losses every 5 to 6 years. Improving human welfare under such circumstances should focus on creating a virtuous cycle based on more timely livestock sales, alternative investment of revenues, and sustainable economic diversification.
    • Valuing grazing use on public land

      Bartlett, E. T.; Torell, L. A.; Rimbey, N. R.; Van Tassell, L. W.; McCollum, D. W. (Society for Range Management, 2002-09-01)
      The value of public land forage has been of key interest since grazing fees were first established on federal lands. Additionally, knowing the value of rangeland forage is important for assessing the economics of range improvements, grazing systems, and alternative land uses. It is important for resource value comparisons and impact assessments when public land forage is allocated to other uses. In this synthesis paper, we review the various methods that have been used to value public land forage and discuss the advantages and limitations of each. We highlight that past valuation efforts have concentrated on the value of public land forage for livestock production and, consequently, underestimated total forage value and rancher willingness to pay for forage and grazing permits. These research efforts failed to recognize that amenity and lifestyle attributes from ranch ownership and forage leasing play important roles in the use and pricing of rangeland forage. We review the numerous studies conducted to estimate public land forage value and suggest modifications to improve future value estimates. Because lifestyle attributes of ranch ownership have so strongly influenced ranch values and what ranchers are willing to pay for grazing use on public lands, we find the market value of federal grazing permits and a modification of the standard contingent valuation method for valuing non-market goods to hold the greatest promise for valuing public land grazing.
    • Quality and persistence of forages in the Northern Great Plains

      Haferkamp, M. R.; Grings, E. E.; Heitschmidt, R. K.; MacNeil, M. D. (Society for Range Management, 2002-09-01)
      Integrating use of seedings of perennial cool-season grasses with native range is used to increase available forage and for maintaining a high plane of nutrition for grazing livestock. Our goal was to evaluate performance of yearling cattle and stand persistence of 3 released wheatgrass cultivars. Twice replicated 3-ha pastures were seeded to 'Rosana' western wheatgrass [Pascopyron smithii (Rydb.) A. Love], 'Luna' pubescent wheat-grass [Elytrigia intermedia (Host) Nevski], and 'Hycrest' crested wheatgrass ([Agropyron cristatum (L.) Gaertn.] ssp. desertorum (Fisch. ex Link) A. Love) in autumn 1994. Yearling steers (n = 8) grazed from 9 May to 12 June 1997 and 24 April to 15 June 1998. Yearling heifers grazed from 27 April to 18 June 1999. Hycrest produced the largest herbage standing crop in spring 1997 (912 kg ha(-1)) and 1998 (1,223 kg ha(-1)) (P < 0.05), but by spring 1999 standing crops averaged 656 kg ha(-1), and cultivars were not significantly different. Digestible organic matter standing crop did not differ among pastures of seeded species, but declined (P < 0.05) from May to June each year. Crude protein standing crop varied among cultivars (P < 0.05) in April and May 1998 and May 1999; however, no clear trends emerged. Crude protein standing crops consistently declined from April-May to June. Average daily gains were similar among cultivars in 1997, but greater (P < 0.05) on Hycrest (1.28 kg day(-1)) than Rosana (1.03 kg day(-1)) in 1998. Gains on Hycrest (0.74 kg day(-1)) and Rosana (0.78 kg day(-1)) were greater (P < 0.05) than on Luna (0.52 kg day(-1)) in 1999. These findings show in some years, Hycrest provided more forage in spring than Rosana, and will allow an increase in livestock numbers. Based on the encroachment of invading species, persistence of Luna is marginal of the 335-mm precipitation zone in the Northern Great Plains.
    • Evaluation of habitat structural measures in a shrubland community

      Harrell, W. C.; Fuhlendorf, S. D. (Society for Range Management, 2002-09-01)
      Accurate and efficient monitoring of habitat structure on rangelands is important for understanding wildlife responses to land management practices. Unfortunately, studies of wildlife responses to changes in habitat structure often use monitoring techniques that fail to measure variation in multiple structural dimensions. Our objectives were to evaluate relationships between measures of habitat structure in a shrubland community and to discuss the usefulness of several techniques in integrating multiple structural dimensions into a single index of habitat structure. We evaluated relationships between shrub cover, herbaceous cover, shrub patch number, average shrub patch size, average vegetation height, visual obstruction across multiple strata of a profile board, cone of vulnerability, and angle of obstruction using a principle component analysis. Many of these variables were redundant with each other. Average visual obstruction estimates, using a profile board, were associated with variability in vertical structure as indicated by its association with height. Coefficients of variation for cone of vulnerability and visual obstruction were dependent upon their means and of limited use in describing horizontal patchiness. In contrast, shrub patch number was not linearly correlated with any other single measure in our analysis, and may be useful in describing horizontal patchiness. Cone of vulnerability and angle of obstruction are recently developed techniques that provided useful, single indices of multidimensional habitat structure. Efficient monitoring of wildlife habitat structure should employ multiple, independent techniques that measure distinct dimensions of habitat structure or a single measure that integrates multiple dimensions.
    • Estimating soil water content in tallgrass prairie using remote sensing

      Starks, P. J.; Jackson, T. J. (Society for Range Management, 2002-09-01)
      Increased demand for available water supplies necessitates that tools and techniques be developed to quantify soil water reserves over large land areas as an aid in management of water resources and watersheds. Microwave remote sensing can provide measurements of volumetric water content of the soil surface (theta(vSL)) up to about 10 cm deep. The objective of this study was to examine the feasibility of inferring the volumetric water content of the soil profile (theta(vBL)) by combining remotely sensed estimates of theta(vSL), in situ measurements, and modeling techniques. A simple soil water budget model was modified to estimate theta(vBL) from assimilated values of theta(vSL). Four modeling scenarios were evaluated at 4 tallgrass prairie sites located in central and south central Oklahoma: 1) unmodified model, 2) assimilation of field-measured theta(vSL) at 2-day intervals, 3) assimilation of field-measured theta(vSL) matching dates of remote sensing data acquisitions during the study period, and 4) assimilation of remotely sensed theta(vSL). The unmodified model (scenario 1) underestimated measurements with root mean square errors (RMSE) between 0.03 and 0.06 m3m(-3) and mean errors (ME) between 0.02 and 0.04 m3m(-3). Model output from scenario 2 agreed well with measurements at all study sites (ME less than or equal to 0.01 m3m(-3), RMSE less than or equal to 0.03 m3m(-3)). The RMSE and ME values from scenario 3 were comparable to those of scenario 2. Simulations from scenario 4 agreed well with measured data at 2 study sites (0.00 m3m(-3) greater than or equal to ME less than or equal to 0.02 m3m(-3), RMSE less than or equal to 0.03 m3m(-3)) but underestimated measurements at the remaining sites, in one case by as much as 0.15 m3m(-3). The underestimation was due largely to inaccurate remotely sensed theta(vSL) values. These preliminary results suggest that it is feasible to infer theta(vSL) in tallgrass prairies by combining remotely sensed estimates of theta(vSL), in situ field measurements, and modeling, provided that the remotely sensed data correctly estimates surface conditions.
    • Vegetation dynamics following seasonal fires in mixed mesquite/acacia savannas

      Owens, M. K.; Mackley, J. W.; Carroll, C. J. (Society for Range Management, 2002-09-01)
      Fires were once a natural part of most savanna ecosystems, but lack of fine fuel and an active suppression policy have changed fire frequency and seasonality. Re-introducing fires to these systems has been touted as a cost-effective means to reduce woody cover while increasing herbaceous growth. We compared the effects of single, recurring annual, and biennial fires on the vegetation dynamics of a mixed mesquite/acacia (Prosopis/Acacia) savanna in southern Texas. Fires were conducted either during the growing season or the dormant season from 1991 through 1995. Some of the fire treatments were statistically unreplicated to permit a sufficient plot size for natural fire behavior. All plots showed a successional trajectory from short-grasses towards mid-grasses regardless of the fire season or frequency. The population size structure of perennial grasses was unaffected by the fires, with the basal area of most plants being less than 25 cm2. Forb diversity was high with over 100 different species identified in the experimental area. Forb composition, however, was unaffected by either the season or frequency of fire, but was related to the year of observation. Shrubs in this community typically sprout after disturbance, so little mortality was expected. The only observed mortality was of small shrubs or saplings (diameter < 3 cm) and of large trees which had woodrat (Neotoma micropus) nests at the base. Reintroducing growing season fires into mesquite/mixed acacia shrublands did not conclusively alter plant community composition. Burning during the growing season when environmental conditions were hotter and drier did not accelerate succession toward grass-dominated communities.
    • Vegetation of prairie dog colonies and non-colonized shortgrass prairie

      Winter, S. L.; Cully, J. F.; Pontius, J. S. (Society for Range Management, 2002-09-01)
      Black-tailed prairie dogs have declined by 98% in the past century. Due to continued declines, the U. S. Fish and Wildlife Service designated the species as a candidate for listing in 2000. Prairie dogs foster both plant and animal diversity, and their continued presence is a concern in the Great Plains. We compared vegetation structure and composition of black-tailed prairie dog (Cynomys ludovicianus Ord) colonies in southwest Kansas and southeast Colorado to non-colonized grassland in 1996, and 1997. Dominant species on prairie dog colonies were Bouteloua gracilis (H. B. K.) Lag. ex Griffiths (14% cover in 1996, 15% in 1997), Buchloe dactyloides (Nutt.) Engelm. (7% cover in 1996, 17% in 1997) and Aristida purpurea Nutt. (9% cover in 1996, 16% in 1997). Dominant vegetation at randomly selected non-colonized sites were Bouteloua curtipendula (Michx.) Torr. (16% cover in 1996, 18% in 1997), Bouteloua gracilis (13% cover in 1996, 17% in 1997) and Buchloe dactyloides (5% cover in 1996, 5% in 1997). Non-colonized shortgrass sites were dominated by Bouteloua gracilis (23% cover in 1996, 41% in 1997) and Buchloe dactyloides (8% cover in 1996, 12% in 1997). Cover of grass was higher (P < 0.01) on random sites (44%) than on prairie dog colonies (31%) or shortgrass sites (33%) in 1996, whereas cover of forbs was higher (P < 0.01) on prairie dog colonies (18%) than on random sites (7%) or shortgrass sites (8%) that year. Vegetation height was greater (Q = 3.66) and visual obstruction was greater (Q = 3.39) on random sites (33.6 and 6.4 cm, respectively) than on prairie dog colonies (9.5 and 2.5 cm, respectively) in 1997, the only year these variables were measured. Percent bare ground did not differ (P > 0.05) among treatments either year. While components of the vegetation on prairie dog colonies differed from that found on non-colonized sites, the vegetation of prairie dog colonies was, nonetheless, characteristic of a shortgrass region. Prairie dogs undoubtably alter vegetation structure and composition in shortgrass prairie, and likely have a great influence on landscape heterogeneity, but our results suggest that shortgrass prairie is well adapted to the herbivory and soil disturbing activities of prairie dogs.
    • A robust model for estimating standing crop across vegetation types

      Vermeire, L. T.; Ganguli, A. C.; Gillen, R. L. (Society for Range Management, 2002-09-01)
      Some recent investigations have shown the visual obstruction (VO) measurement method to be an effective means of estimating herbage standing crop non-destructively in tallgrass prairie. Although the method is rapid and inexpensive, visual obstruction models have been limited to tallgrass prairie and sandhills range types. Our primary objective was to evaluate the relationships between visual obstruction and standing crop in shortgrass plains and mixed prairie. Secondly, we wanted to determine whether these models could be integrated with tallgrass prairie models without appreciable losses in prediction capabilities. We conducted 44 trials on non-burned sites with various levels of grazing pressure. Each trial was composed of 20 randomly selected plots and served as 1 experimental unit to represent pasture-level standing crop estimation. Visual obstruction readings were taken from a modified Robel pole placed centrally at the back of 0.1-m2 quadrats and vegetation was clipped to estimate standing crop. Trial standing crop was regressed on visual obstruction and models were compared among range types. Visual obstruction explained 91 and 89% of the variation in shortgrass plains and mixed prairie standing crop, respectively. A single visual obstruction model effectively estimated herbage standing crop across range types and produced a coefficient of determination of 0.93. Although greater precision may be obtained from models developed for specific sites, the ability of a single visual obstruction model to predict standing crop across years, management schemes, and range types indicates visual obstruction models may be successfully employed on a regional basis.
    • Response of C3 and C4 grasses to supplemental summer precipitation

      Skinner, R. H.; Hanson, J. D.; Hutchinson, G. L.; Schuman, G. E. (Society for Range Management, 2002-09-01)
      Rangeland plant productivity and species composition are affected by moisture availability and grazing intensity. We examined warm- and cool-season grass productivity and relative distribution on grazed and ungrazed sites, receiving either natural precipitation or precipitation plus limited supplemental irrigation. The amount of additional water varied depending on rainfall during the previous week and was intended to shorten the interval between precipitation events and provide a more uniform seasonal moisture distribution. Irrigation treatments were superimposed in 1997 and 1998 on paddocks that had not been grazed for about 55 years or continuously stocked during the growing season for 15 years. Cool-season grasses dominated the ungrazed plots, comprising about 90% of the total biomass. In the grazed plots, the proportion of C3 grasses ranged from 30 to 81%. The proportion of C3 grasses in the grazed treatment decreased from spring to fall and decreased with supplemental irrigation. Root biomass was greater and more concentrated near the soil surface in the grazed compared with the ungrazed plots. Irrigation had no effect on root biomass in the grazed plots while irrigation reduced total root biomass and root biomass in the top 5 cm of the soil profile in the ungrazed plots. Irrigation increased total aboveground biomass only at the August 1997 harvest. Aboveground biomass of warm-season grasses, however, increased under irrigation in the grazed plots in August and November 1997 and August 1998. These increases, however, were offset by a reduction in cool-season grasses in November 1997 and August 1998. Warm-season grasses were particularly responsive to the supplemental irrigation treatments and tended to increase under irrigation at the expense of cool-season grasses. Because of the increased proportion of warm-season grasses, grazed plots were more responsive to irrigation than ungrazed plots.