• Brangus Cow-Calf Performance Under Two Stocking Levels on Chihuahuan Desert Rangeland

      Thomas, Milt; Hawkes, Jerry; Khumalo, Godfrey; Holechek, Jerry L. (Society for Range Management, 2007-01-01)
      Cow-calf productivity on 2 lightly (25%-30% use) and 2 conservatively grazed pastures (35%-40% use) were evaluated over a 5-year-period (1997 to 2001) in the Chihuahuan Desert of south-central New Mexico. Spring calving Brangus cows were randomly assigned to study pastures in January of each year. Experimental pastures were similar in area (1 098 +/- 69 ha, mean +/- SE) with similar terrain and distance to water. Use of primary forage species averaged 28.8% +/- 4.3% in lightly stocked pastures and 41.8% +/- 4.4% on conservatively grazed pastures. Perennial grass standing crop (168.8 +/- 86 vs. 173.6 +/- 58.3 kg ha-1) and adjusted 205-day calf weaning weights (279.1 +/- 7.5 vs. 270.7 +/- 7.8 kg) did not differ among lightly and conservatively grazed pastures. Cow body condition scores in autumn, winter, and spring were similar among grazing levels as were autumn and winter body weights. However, cow body weights tended to be heavier (P < 0.10) in lightly grazed pastures relative to conservatively grazed pastures (524 vs. 502 +/- 9.7 kg) in spring. Lightly grazed pastures yielded greater (P < 0.05) kg of calf weaned ha-1 and calf crop percent than conservatively grazed pastures in 1998 due to destocking of conservatively grazed pastures during that year’s drought. Conversely, pregnancy percent tended to be greater (P < 0.1) in conservatively relative to lightly grazed pastures (92.6% vs. 87.7%); however, this advantage is explained by herd management as cows in the conservatively grazed pastures were removed during drought of 1998, avoiding exposure to the drought stress experienced by cows in the lightly grazed pastures. Nonetheless, pregnancy percents from both grazing treatments would be acceptable for most range beef production systems. Results suggest that consistently applying light grazing use of forage is a practical approach for Chihuahuan Desert cow-calf operations to avoid herd liquidation during short term drought. 
    • Diet Composition of Cattle Grazing Sandhills Range During Spring

      Volesky, Jerry D.; Schacht, Walter H.; Reece, Patrick E.; Vaughn, Timothy J. (Society for Range Management, 2007-01-01)
      The 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. 
    • Effects of Cattle Stocking Rates on Nematode Communities in South Florida

      McSorley, Robert; Tanner, George W. (Society for Range Management, 2007-01-01)
      Ranch management practices aimed at cattle and pasture vegetation have the potential to impact other animals as well, including nontarget organisms. Soil-inhabiting nematodes are often used as bioindicators of nontarget effects because of their widespread occurrence and their diverse trophic habits and lifestyles. The effect of cattle stocking rates on nematode communities present in the soil was examined at the MacArthur Agro-Ecology Research Center in south-central Florida. Nematode abundance and richness (genera per sample) were not affected (P > 0.10) by cattle grazing in 2 different pasture types (tame grass and native) over three seasons. In general, populations of most nematodes showed strong seasonal responses, varying in numbers from year to year, possibly related to soil moisture levels. In comparison, the cattle stocking rates typically used in south-central Florida had little effect on soil nematodes, which were abundant nontarget organisms in this system. 
    • Evaluation of Low-Moisture Blocks and Conventional Dry Mixes for Supplementing Minerals and Modifying Cattle Grazing Patterns

      Bailey, Derek W.; Welling, G. Robert (Society for Range Management, 2007-01-01)
      Two studies were conducted to evaluate the effectiveness of low-moisture blocks (LMB) and conventional dry mixes (CDM) for supplementing minerals to cattle on rangeland and to modify grazing patterns. In study 1, cows were fed LMB or CDM on moderate or difficult foothill terrain in Montana during autumn and winter. Cows consumed more CDM in moderate terrain than difficult terrain, but intake of LMB was similar in both terrain types. Using global positioning system (GPS) telemetry data, visits to supplements were defined as collared cow positions within 10 m of placement sites. More cows visited LMB (74%) than CDM (56%). More cows visited supplements (LMB and CDM pooled) when placed in moderate rather than difficult terrain. Cows spent more nonresting time within 100 and 200 m of LMB than CDM. In study 2, CDM and LMB designed to supplement minerals (LMB-M) were compared when cows were also fed LMB designed to supplement protein (LMB-P). Comparisons were made with cows grazing rangeland and with cows fed hay. Intake of LMB-P and CDM was less when cows grazed rangeland than when they were fed hay. Cows consumed less LMB-P when LMB-M was available. More cows visited LMB-M than CDM, and cows visited LMB-M more frequently than CDM. The LMB formulations designed to supplement minerals work well with formulations designed to supplement protein. Both LMB and CDM met estimated deficits of minerals in the forage based on supplement intake (g day-1) and forage evaluations, but cows visited LMB more consistently than CDM. Low-moisture blocks appear to be more attractive to cows than CDM and should be more useful to modify grazing patterns on rangeland. 
    • Influence of 90 Years of Protection From Grazing on Plant and Soil Processes in the Subalpine of the Wasatch Plateau, USA

      Gill, Richard A. (Society for Range Management, 2007-01-01)
      Human communities in the Intermountain West depend heavily on subalpine rangelands because of their importance in providing water for irrigation and forage for wildlife and livestock. In addition, many constituencies are looking to managed ecosystems to sequester carbon in plant biomass and soil C to reduce the impact of anthropogenic CO2 on climate. This work builds on a 90-year-old grazing experiment in mountain meadows on the Wasatch Plateau in central Utah. The purpose of this study was to evaluate the influence of 90 years of protection from grazing on processes controlling the input, output, and storage of C in subalpine rangelands. Long-term grazing significanty reduced maximum biomass in all years compared with plots within grazing enclosures. For grazed plots, interannual variability in aboveground biomass was correlated with July precipitation and temperature (R2 – 0.51), while there was a weak correlation between July precipitation and biomass in ungrazed plots (R2 – 0.24). Livestock grazing had no statistically sinificant impacts on total soil C or particulate organic matter (POM), although grazing did increase active soil C and decrease soil moisture. Grazing significantly incrased the proportion of total soil C pools that were potentially mineralizable in the laboratory, with soils from grazed plots evolving 4.6% of total soil C in 1 year while ungrazed plots lost 3.3% of total soil C. Volumetric soil moisture was consistently higher in ungrazed plots than grazed plots. The changes in soil C chemistry may have implications for how these ecosystems will respond to forecast climate change. Because grazing has resulted in an accumulation of easily decomposable organic material, if temperatures warm and summer precipitation increases as is anticipated, these soils may become net sources of CO2 to the atmosphere creating a positive feedback between climate change and atmospheric CO2.
    • Integrated Ecological and Economic Analysis of Ranch Management Systems: An Example From South Central Florida

      Swain, Hilary M.; Boblen, Patrick J.; Campbell, Kenneth L.; Lollis, Laurent O.; Steinman, Alan D. (Society for Range Management, 2007-01-01)
      Developing sustainable ranch management systems requires integrated research that examines interrelations among ecological and economic factors. In south central Florida, where phosphorus (P) loading is an overriding environmental concern, we established an interdisciplinary experiment to address the effects of cattle stocking density and pasture type on P loading and other ecological and economic factors in subtropical Florida ranchlands through a partnership including ecologists, agricultural faculty, agency personnel, and producers. Here we present an overview of all project components detailed in 3 accompanying papers in this issue of Rangeland Ecology Management. We describe the experimental design, which included 2 replicates of 4 different cattle stocking density treatments (control, low, middle, and high [0, 15, 20, and 35 cow-calf pairs per pasture]) maintained on 8 improved summer pastures (– 20 ha each), and 8 seminative winter pastures (– 32 ha each) from 1998 to 2003. Stocking densities did not significantly affect P loads and concentrations in surface runoff, soil chemistry, or soil nematode communities, but did affect cattle production and economic performance. Cattle production was greater at the high than at the middle or low stocking density; economic performance declined significantly with decreasing stocking density (break-even was 1.89 kg-1 for high and 2.66 kg-1 for low density). Pasture type significantly affected environmental factors; average P runoff from improved summer pastures (1.71 kg P h-1 y-1) was much greater than from seminative winter pastures (0.25 kg P ha-1 y1), most likely because of past P fertilizer use in improved pastures. We integrate results from all the papers within the context of a conceptual model and a P budget, and emphasize that management practices targeted at specific environmental factors on beef cattle ranches, such as nutrient loading, must include consideration of economic impacts and broader ecosystem implications. 
    • Integrating Ranch Forage Production, Cattle Performance, and Economics in Ranch Management Systems for Southern Florida

      Arthington, J. D.; Roka, F. M.; Mullahey, J. J.; Coleman, S. W.; Muchovej, R. M.; Lollis, L. O.; Hitchcock, D. (Society for Range Management, 2007-01-01)
      The presence of grazing cattle near open waterways has created environmental concerns related to the potential for water contamination. In Florida the removal of cattle from grazing landscapes or decreasing stocking density is being investigated as one option to improve the quality of surface water runoff draining into Lake Okeechobee, Florida. The objective of this study was to determine the effects of stocking rate on cow-calf performance, forage availability and quality, and ranch economic performance. Experimental pastures were established on a southern Florida cow-calf operation with stocking rates of 0.58, 1.01, and 1.35 ha cow-1 on summer pastures and 0.93, 1.62, and 2.16 ha cow-1 on winter pastures, corresponding to high, medium, and low rates, respectively. The study was conducted over 4 consecutive production years. Cow body condition scores (BCS), pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside and outside grazing exclusion cages and forage quality by crude protein and in vitro organic matter digestibility. Forage yield, utilization, and quality were not significantly affected by stocking rate. Although statistically not significant (P = 0.17), cattle in the high stocking rate experienced a numerically greater loss of BCS following the winter grazing period, but stocking rate did not affect pregnancy rate or calf gains. Production (kg weaned calves ha-1) was increased (P < 0.01) for a high stocking rate compared with medium and low stocking rates. Overall ranch profitability will decrease as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch’s fixed cost structure. 
    • Livestock Forage Conditioning Among Six Northern Great Basin Grasses

      Ganskopp, Dave; Aguilera, Lisa; Vavra, Martin (Society for Range Management, 2007-01-01)
      Studies 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. 
    • Monoterpene Production in Redberry Juniper Foliage Following Fire

      Campbell, E. S.; Taylor, C. A. (Society for Range Management, 2007-01-01)
      Prescribed fire is commonly used to initiate redberry juniper (Juniperus pinchotti Sudw.) suppression, and herbivory by goats presents a potentially effective mechanism to prolong the efficacy of the reclamation treatment. Monoterpenes in redberry juniper leaves serve as a barrier to effective herbivory, but fire has the potential to reduce this barrier through reversion of aboveground growth to juvenile tissue. Traditional optimal defense theory predicts that because of the assumed fitness value of vegetative regrowth, plant secondary chemicals will be higher in this tissue than mature growth. This study was designed to measure the monoterpene concentration and composition from redberry juniper foliage sampled from 3 different ages of plant tissue. Prescribed fire was used to create 3- and 11-month regrowth juniper foliage, and mature growth of juniper was sampled as a control. Total monoterpene levels were lowest in the 3-month regrowth (P = 0.018). Monoterpene concentration and composition was similar for the 11-month and mature foliage. Concentration of terpinen-4-ol (P = 0.001) and alpha-terpineol (P = 0.007), identified as particularly aversive monoterpenoids to goats, was lowest in the 3-month regrowth but increased to levels found in mature leaves by 11 months of age. There was a trend in changes in composition of total oil as relative concentrations of monoterpene hydrocarbons (a-pinene, b-pinene/sabinene) decreased and monoterpene alcohols and oxygenated monoterpenes increased. These results identify a short period of time following a burn during which monoterpene levels in regrowth are low. This suggests a period of vulnerability in plant biochemical defenses that has the potential to be utilized by strategic herbivory by goats for more effective juniper management. 
    • Potential Outcomes and Consequence of a Proposed Grazing Permit Buyout Program

      Steinbach, Mark S.; Thomas, Jack Ward (Society for Range Management, 2007-01-01)
      This study investigated the role that a public land grazing permit buyout would have on ranching operations and conserving private land open space in the Rocky Mountain region of the western United States. Loss of grazing permits could serve as a pivotal factor in expediting private land fragmentation if ranching operations are enticed to sell their land due to loss of economic viability. This type of program inadvertently could be detrimental to overall ecosystem health and have unintended economic, ecological, and cultural consequences for the administering agencies and grazing permittees. The goal of this study was to provide sociodemographic profiles of landowners to better understand social motivations for ranching, implications of permit removal, ongoing conservation activities, and possible policy solutions. We assessed likely participation levels, demographic attitudes, and reasons for participation in a proposed grazing permit buyout program. This paper is based on data collected from a mail survey of 2 000 permittees in the Rocky Mountain States (39% response rate), and data collected from qualitative personal interviews. These interviews assessed motivations for participation, potential costs, and search for unforeseen consequences related to a proposed buyout program. We interviewed 49 individuals (33 ranchers, 16 agency personnel), which enabled us to describe likely outcomes and previously unmentioned items for consideration related to a proposed buyout program. Interview data were analyzed and broken into two major themes: motivation for participation in a buyout and potential consequences. Our study indicated that overall participation in potential buyout would be relatively low (17%); however, the associated financial, ecological, and administrative costs could be substantial. We note several unanticipated motivations for possible participation in this type of program, as well as possibly unrecognized impacts for administering agencies and permittees. 
    • Seed Shatter Dates of Antelope Bitterbrush in Oregon

      Johnson, G. R.; Berrang, Paul C. (Society for Range Management, 2007-01-01)
      Seed shatter dates for antelope bitterbrush (Purshia tridentata [Pursh] DC) were estimated from collections at 192 sites in Oregon and surrounding states. Shatter date was strongly correlated to elevation (r = 0.74) and an equation that included elevation, latitude, longitude, and longitude squared explained 79% of the variation in seed shatter dates. In general, earlier shatter dates were associated with more southerly latitudes, easterly longitudes, and lower elevations. Examination of climatic data confirmed the expectation that earlier shatter dates were associated with warmer sites. This information can assist those needing to schedule seed collection activities at multiple locations. 
    • Soil Phosphorus, Cattle Stocking Rates, and Water Quality in Subtropical Pastures in Florida, USA

      Capece, John C.; Campbell, Kenneth L.; Behlen, Patrick J.; Graetz, Donald A.; Portier, Kenneth M. (Society for Range Management, 2007-01-01)
      Minimizing nonpoint source nutrient pollution is important to the sustainability of grazing lands. Increased nutrient loads have reduced water quality in Lake Okeechobee in south Florida, prompting establishment of a Total Maximum Daily Load (TMDL) that will require large reductions in phosphorus (P) runoff into the lake. A significant portion of this reduction must come from beef cattle ranches, the major land use in the region. A large-scale research project, consisting of a 420-ha array of 8 improved summer and 8 semi-improved winter pastures, was established from 1998-2003 to investigate the influence of beef cattle stocking rate on nutrient loads in surface runoff. Each pasture type had two replicates of four different cattle stocking rates including a control with no cattle and stocked pastures with low, medium, and high stocking rates (1.3, 1.0, 0.6 ha AU-1 [animal unit] in summer pastures; 2.1, 1.6, and 0.9 ha AU-1 in winter pastures). Cattle stocking rate did not affect nutrient concentrations or loads in surface runoff during the study period. Average annual P discharges were 1.71 kg ha-1 from summer pastures and 0.25 kg ha-1 from winter pastures. Average total P concentrations in runoff were 0.63 mg L-1 for summer pastures and 0.15 mgL-1 for winter pastures. Differences in runoff P were related to differences in soil P test results, a difference believed to be due to prior fertilization practices. Our findings show that reducing cattle stocking rates on beef cattle pastures is not an effective practice for reducing nutrient loads, and that accumulation of P in soil from historical fertilization has an overriding influence on P loads in surface runoff. Results indicate that reducing the overall volume of surface discharges would be a more effective strategy than altering cattle stocking practices to reduce nonpoint runoff of P from cattle pastures in this region. 
    • Soil Water Content Dynamics Along a Range Condition Gradient in a Shortgrass Steppe

      Medina-Roldán, Eduardo; Moreno, J. Tulio Arredondo; Moya, Edmundo García; Martínez, F. Martín Huerta (Society for Range Management, 2007-01-01)
      Evidence is accumulating on the importance of plant cover and plant species composition on the control of ecosystem processes. In this study we examined a gradient considering the proportional contribution of the key species Bouteloua gracilis H.B.K. Lag. to assess its influence on the average and dynamic changes in soil water content in the shortgrass steppe from Central Mexico. We chose 4 sites with the following proportions of the key species: < 25%, 25%-50%, 50%-75%, and > 75%, ascribing each proportion to the range condition categories poor, fair, good, and excellent, respectively. Soil water measurements were carried out during 14 months at the 4 sites. Our results showed that range condition had a significant effect on soil water content (P < 0.01). The excellent condition was overall 14.5% and 12.5% lower soil moisture content compared to the poor and good range conditions (P < 0.01), respectively. Our results indicated a negative correlation between the gradient of soil water content with the range condition classes. Soil water content dynamics also differed among range condition classes, with the excellent condition showing both faster water recharge and extraction patterns than the other 3 range condition categories. Differences in soil water content among the range condition classes appeared to be related to morphological and physiological traits associated with the dominant species cover observed at each site. These results offer insights into the importance of vegetation char- acteristics as potential indicators of thresholds in grazing ecosystem processes such as soil water dynamics. 
    • Utilizing Remote Sensing and GIS to Detect Prairie Dog Colonies

      Assal, Timothy J.; Lockwood, Jeffrey A. (Society for Range Management, 2007-01-01)
      The locations of black-tailed prairie dog (Cynomys ludovicianus [Ord]) colonies on a 550-km2 study site in northeastern Wyoming, United States, were estimated using 3 remote sensing methods: raw satellite imagery (Landsat 7 ETM+), enhanced satellite imagery (integration of imagery with thematic layers via a Geographic Information System), and aerial reconnaissance (observations taken from a small plane). A supervised classification of the raw satellite imagery yielded an overall accuracy of 64.4%, relative to ground-truthed locations of prairie dog colonies. The enhanced satellite imagery, resulting from a filtering of the data based on an index derived from the sum of weighted ecological factors associated with prairie dog colonies (slopes, land cover, soil, and ‘‘greenness’’ via the Normalized Difference Vegetation Index) yielded an overall accuracy of 69.2%. The aerial reconnaissance method provided 65.1% accuracy. The highest rate of false positives resulted from the aerial reconnaissance method (39.9%). The highest rate of false negatives resulted from the raw satellite imagery (60.0%), a value that was markedly reduced via the enhancement with ecological data from thematic layers (45.8%). Given the accuracy, interpretability of results, repeatability, objectivity, cost, and safety, the enhanced satellite imagery method is the recommended approach to large-scale detection of black-tailed prairie dog colonies. If a greater accuracy is required, this method can be employed as a coarse filter to narrow the scale and scope of a more costly and laborious fine-scale analysis effectively.