• The Effect of Agriculture on Ferruginous and Swainson's Hawks

      Schmutz, J. K. (Society for Range Management, 1987-09-01)
      Raptors are an important component of prairie ecosystems. I examined the effects of grassland conversion to agricultural fields on densities of nesting prairie hawks. Densities of Swainson's hawks were recorded for comparison. The 2 species of congeneric hawks responded differently to habitat loss despite considerable overlap in their use of resources. As cultivation on study plots increased, ferruginous hawks declined. Swainson's hawks were more abundant in areas of moderate cultivation than in grassland or in areas of extensive cultivation. Differences in the hawks' responses were attributed to differences in their ecology, primarily prey utilization. There was no evidence that soil quality affected hawk abundance.
    • Steer and Vegetation Response to Short Duration and Continuous Grazing

      Pitts, J. S.; Bryant, F. C. (Society for Range Management, 1987-09-01)
      Comparisons were made over a 4-year period between 1-herd, 16-pasture short duration grazing (SDG) and continuous grazing (CG) on the Texas High Plains. Animal performance, vegetation response, and diet quality were evaluated. Stocking rate on SDG was equal to that on CG the first year (13.3 ha/AU), double that on CG in the second year, and 1.5 times that on CG the third and fourth years. Average daily gain (ADG) of steers was the same (0.33 kg/day) between SDG and CG the first year. When stocking was doubled on SDG the second year, steers on SDG gained 0.15 kg/day compared to 0.25 kg/day under CG. In the third and fourth years, with stocking under SDG at 1.5 times that on CG, gains were similar. Standing crop biomass on SDG fell below that on CG after 1 year of grazing. In the second year standing crop was greater (P<0.05) on SDG than on CG, but in years 3 and 4, standing crop on the SDG was less than on CG. Changes in species composition were the same on both CG and SDG. Steer diet composition and quality were evaluated during the growing season (May to October) of year 4. Steers on SDG consumed 15% more forbs (39% vs 24%) than steers on CG. No differences (P>0.05) between CG and SDG were observed for dietary crude protein or in vitro digestible organic matter. SDG did not improve animal performance, diet quality, or forage availability over CG when evaluated over 4 years.
    • Vegetation Trends within Rest-Rotation and Season-long Grazing Systems in the Missouri River Breaks, Montana

      Watts, C. R.; Eichhorn, L. C.; Mackie, R. J. (Society for Range Management, 1987-09-01)
      Trends in canopy-coverage of vegetation and bare ground were measured inside and outside exclosures on recent burns within three-pasture rest-rotation and season-long grazing systems over a 10-year period. Results suggested that rest-rotation grazing may maintain vegetation and soil cover somewhat comparable to ungrazed cattle exclosures on rough breaks-type range in north-central Montana. Season-long grazing may not maintain satisfactory vegetation and soil cover in the area.
    • Changes in Concentrations of Tannins, Total Phenolics, Crude Protein, and In Vitro Digestibility of Browse due to Mastication and Insalivation by Cattle

      Burritt, E. A.; Malechek, J. C.; Provenza, F. D. (Society for Range Management, 1987-09-01)
      The feasibility of using esophageal extrusa to monitor dietary tannin levels was studied using 4 shrub species (Purshia tridentata, Quercus gambelii, Cercocarpus montanus and Acer grandidentatum). Browse samples were hand-harvested in late summer. Half of the sample for each species was fed to esophageally fistulated cattle, while the other half served as an unmasticated control. Extrusa and control samples were analyzed for total phenolics (Folin-Denis), tannin using 3 methods (vanillin-HCl, proanthocyanidins, and astringency), crude protein, and in vitro organic matter digestibility (IVOMD). Tannin levels were reduced 10% to 60% in extrusa, depending on plant species and method of tannin analysis. Changes in the nutritional constituents of extrusa were limited but oak extrusa was higher in IVOMD than oak control samples. Tannins may have bound to plant or salivary proteins or to mucous membranes in the mouth during mastication and insalivation. Our results indicate that esophageal extrusa is not suitable for monitoring dietary tannin levels.
    • Clearcutting Brazilian Semiarid Tropics: Observations on Its Effects on Small Ruminant Nutrition during the Dry Season

      Kirmse, R. D.; Provenza, F. D.; Malechek, J. C. (Society for Range Management, 1987-09-01)
      Small ruminant production in northeast Brazil is limited by prolonged nutritional stress during the dry season. Our study assessed the effects of clearcutting woody vegetation on the nutrition of goats and sheep during the initial dry season following clearing. Dry matter intake g day-1 was higher for animals on cleared than on uncleared areas (818 vs. 627; P<0.05). Extrusa from esophageally fistulated animals grazing cleared, as opposed to uncleared, areas was more digestible (52 vs. 47%; P<0.05), was similar in crude protein (7.1 vs. 7.1%; P<0.05), and was lower in neutral detergent fiber (49 vs. 51%; P<0.05) and lignin (14 vs. 16%; P<0.05). Intake and diet quality declined on both cleared and uncleared areas as forage availability declined. Animals on cleared areas benefitted from increased availability of herbs and of biomass from palatable trees that coppiced and retained green leaves throughout much of the dry season. Animals on uncleared areas relied heavily on leaf litter from trees, which provided a poorer quality, but persistent, source of forage throughout the dry season.
    • An Evaluation of Random and Systematic Plot Placement for Estimating Frequency

      Whysong, G. L.; Miller, W. H. (Society for Range Management, 1987-09-01)
      A computer simulation study was conducted to evaluate the effects of pattern on the precision of frequency estimates as determined from random and systematic plot placement. Computer graphics were used to generate artificial population maps containing 40 or 80 clumps of differing spatial intensity with known frequencies of 20, 35, and 50%. The maps were repeatedly sampled both randomly and systematically using a 200-plot sample size to obtain frequency estimates. Three systematic plot spacings (4, 8, and 12) along randomly located transects were evaluated. Analysis indicated that frequency means from systematic plot placement were significantly affected by clumping, pattern intensity, and plot spacing. Random sampling resulted in frequency means that were unaffected by clumping or pattern intensity, and more consistently estimated population frequencies. An evaluation of probabilities of occurrence of Type I errors when statistically comparing frequency estimates from systematic plot placement indicated higher Type I error rates as compared to random sampling.
    • Atrazine, Spring Burning, and Nitrogen for Improvement of Tallgrass Prairie

      Gillen, R. L.; Rollins, D.; Stritzke, J. F. (Society for Range Management, 1987-09-01)
      Spring application of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] (1.1 kg ha-1 a.i.), burning, and nitrogen (33 kg ha-1 as ammonium nitrate) were evaluated alone and in all combinations for improvement of mid-seral tallgrass prairie in northcentral Oklahoma. Studies were initiated in 1984 (Study I) and 1985 (Study II). Precipitation and successional status of the vegetation at treatment application were higher for Study II than for Study I. Atrazine effectively reduced forbs and annual grasses for 2 years after application. Atrazine stimulated warm-season perennial grasses but did not generally increase total herbage production. Burning was similar to atrazine for annual grass control in both studies. Burning was also similar to atrazine for forb control in Study I but had no impact on forb production in Study II. Burning increased perennial grass production only in the second year of Study I. Burning decreased total herbage production in the first year of Study I by reducing annual grasses and forbs but did not affect total herbage production on other dates. Nitrogen did not consistently increase perennial grass production but did increase forb production by 250-300% when applied alone. Both atrazine and burning rapidly shifted species composition in favor of desirable perennial grasses. Nitrogen was not as effective in changing species composition either alone or in combination with atrazine and burning. The number and complexity of treatment responses declined as successional status and/or precipitation improved.
    • Evaluation of the Forage-disk Method in Mixed-grass Rangelands of Kansas

      Karl, M. G.; Nicholson, R. A. (Society for Range Management, 1987-09-01)
      The forage disk meter, a double sampling device used to predict forage biomass, has been used extensively on improved pastures, but its use on rangelands has not been investigated thoroughly. Efficiency of the forage disk meter was investigated in predicting yields of forage biomass on different range sites in western Kansas. Using least squares regression methods, resting heights (forage bulk) and dry matter yields were used to calibrate the disk meter for each site and sampling date. Highly significant regressions (P<0.0001) were obtained on all the shortgrass sites, where several factors that had unfavorable effects on the regression relationship between forage bulk and forage biomass were not apparent. These factors, although not quantified, included accumulation of litter, microrelief, lodged vegetation, and presence of broadleaf species. Regression coefficients (b) and intercepts (a) varied between sites and dates, thus the forage disk meter should be calibrated for every range site. If a forage disk meter is calibrated for a specific range site, regression coefficients and intercepts might not differ from year to year if grazing pressure and species composition are temporally consistent, which implies that recalibration might be unnecessary. The forage disk meter was useful as a double sampling device on range sites dominated by shortgrasses, but its use was limited on areas dominated by annual forbs or midgrasses.
    • Soil Seed Banks Associated with Individual Broom Snakeweed Plants

      Osman, A.; Pieper, R. D.; McDaniel, K. C. (Society for Range Management, 1987-09-01)
      The influence of individual broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rushby) plants on the distribution of buried viable seed and the distribution of plants in the field was studied in a desert grassland in southern New Mexico. Surface soil samples collected at 3 distances from a central broom snakeweed plant were watered in pots in a greenhouse and numbers of each species emerging were counted. Densities of each species were also determined in the field. Some species (Sporobolus flexuosus [Thurb.] Rybd., S. contractus Hitchc., Descurainia pinnata [Walt.] Britton, and Dithyrea wislizenii Engelm.) emerged in greatest numbers from soil collected in the zones closest and at the greatest distances from the broom snakeweed. Emergence of other species declined in relation to distance from the central snakeweed plant. In the field, grasses generally increased in relation to distance from the central broom snakeweed plant while the pattern for forbs was not consistent.
    • Rainfall Interception by Midgrass, Shortgrass, and Live Oak Mottes

      Thurow, T. L.; Blackburn, W. H.; Warren, S. D.; Taylor, C. A. (Society for Range Management, 1987-09-01)
      Interception, as a function of simulated rainfall intensity and duration, was determined for a midgrass [sideoats grama (Bouteloua curtipendula (Michx.) Torr.)] and a shortgrass [curleymesquite (Hilaria belangeri (Steud.) Nash)]. In addition, the redistribution of natural precipitation via plant interception was determined for live oak (Quercus virginiana Mill.) mottes. Interception storage capacity for sideoats grama and curleymesquite was 81 and 114% of dry weight, respectively. This difference was attributed to physical characteristics of the species and their respective growth forms. However, because sites dominated by sideoats grama had more standing biomass (3,640 kg ha-1) than sites dominated by curleymesquite (1,490 kg ha-1), it was estimated that a sideoats grama dominated site had an interception storage capacity of 1.8 mm compared to curleymesquite dominated site with an interception storage capacity of 1.0 mm. Based upon precipitation event size and distribution for the study site at the Texas Agricultural Experiment Station near Sonora, Texas, the estimated interception loss for curleymesquite dominated sites was 10.8% of annual precipitation, compared to 18.1% interception loss for sideoats grama dominated sites. Only 54% of the annual precipitation reached mineral soil beneath the oak mottes as throughfall or stemflow. The remainder of the precipitation was intercepted by the motte canopy or litter layer and evaporated. Due to the water concentrating effect of stemflow, soil near the base of trees received about 222% of annual precipitation. Soil at a distance greater than approximately 100 mm from a tree trunk received only 50.6% of annual rainfall. Individual tree canopy width, height and depth measurements were insignificant predictors of stemflow and throughfall. Interception, throughfall and stemflow, expressed as percent of storm precipitation, were well-defined curvilinear functions.
    • Nitrogen and Energy Budgets of Free-Roaming Cattle

      Senft, R. L.; Stillwell, M. A.; Rittenhouse, L. R. (Society for Range Management, 1987-09-01)
      Energy and nitrogen (N) budgets of free-roaming yearling heifers were quantified. Energy and N retention were estimated from liveweight gains. Intake and excretion of N and energy were measured directly. Dry matter intake per unit metabolic body weight (MBW = Bwkg.75) varied seasonally, peaking in late growing season. Fecal dry matter output, which was related to dry matter intake, also peaked late in the growing season. Urine volume, however, peaked early in the growing season. Urinary N excretion per MBW was correlated with dietary N concentration (r = .79). Fecal N excretion per MBW was relatively constant while fecal N concentration varied. Partitioning of N losses between feces and urine varied seasonally, with 54% excreted in urine during the growing season (April through October) and 45% in urine during the dormant season (November through March). On a year-round basis, 8% of ingested N was incorporated into body tissue. Fecal energy excretion trend followed that of gross energy intake. Digestible energy intake per MBW was relatively high throughout the growing season and steadily declined after onset of the dormant season. Urinary energy output was closely related to urinary N output and peaked early in the growing season. Metabolizable energy (ME) followed dynamics similar to those of digestible energy. Net energy for liveweight gain accounted for about 8% of gross energy intake on a year-round basis. ME and crude protein intake were above maintenance requirements during the growing season, but were inadequate during the dormant season. ME intake apparently limited growth early in the growing season; protein intake was limiting late in the growing season.
    • Nitrogen Concentration in Blood and Rumen Liquor of Cattle Fed Low Protein Diets

      Hinnant, R. T.; Kothmann, M. M. (Society for Range Management, 1987-09-01)
      Crude protein determination of a grazing animal's diet is difficult and expensive. Traditional methods include forage sampling (usually not representative of the diet selection process) and the use of fistulated animals for direct diet collections. Indirect methods were tested to provide a rapid estimate of diet protein at less cost. Concentration of blood serum urea N (BUN) and the concentration of total nitrogen (N), protein N, microbial protein N, and non-protein N (NPN) in rumen liquor were determined in 4 cows and 4 steers fed diets at maintenance (7.1%) and 3 sub-maintenance levels of crude protein (CP) (4.3, 5.2, and 6.2%). Cottonseed hulls constituted the basal diet, with cottonseed cubes added to vary the CP content and molasses added to provide isocaloric diets. However, diet CP affected the in vivo digestibility of the diets and hence their caloric values. Concentrations of BUN did not differ (P<.05) with changes in dietary CP. The concentration of total N, protein N, microbial protein N, and nonprotein N (NPN) in the rumen liquor (P<.05) increased as diet CP increased. The percentage of NPN in the total N was reduced when diet CP was below 5.2%, but it did not differ significantly when diet CP was between 5.2 and 7.1%. The ratio of microbial nitrogen to total protein nitrogen was not affected by level of dietary crude protein. Total N was a sensitive indicator of the CP content of the diet and was the easiest and quickest method tested.
    • Ytterbium-Labeled forage as a Marker for Estimation of Cattle Fecal Output

      Musimba, N. K. R.; Galyean, M. L.; Holechek, J. L.; Pieper, R. D. (Society for Range Management, 1987-09-01)
      This study evaluated the accuracy of a once daily dose of ytterbium (Yb)-labeled forage as a marker to estimate fecal output of cattle grazing at the National Range Research Station, Kiboko, Kenya. Ytterbium-labeled forage was administered daily to 15 zebu steers for 10 consecutive days for each of 3 trials. During the last 5 days of each trial, fecal grab samples were collected at 6-h intervals. During this same 5-day period, total fecal output was collected from 9 of the steers. Ytterbium estimates of fecal output were 114%, 104%, and 144% of actual fecal output for March, April, and July trials, respectively. Dry matter and organic matter intake estimates between Yb and total collection procedures differed (P<.05) in the July trial, but not the March and April trials. Compared with total fecal collection, Yb overestimated organic matter intake by 20, 2, and 40%, respectively for March, April and July trials. Based on our results, daily dosing of Yb-labeled forage will provide reasonable estimates of fecal output when relative estimates of intake between range management treatments are needed.
    • Effects of Grazing on the Vegetation of the Blackbrush Association

      Jeffries, D. L.; Klopatek, J. M. (Society for Range Management, 1987-09-01)
      Four communities or sites dominated by blackbrush (Coleogyne ramosissima Torr.) were studied in the Kaiparowits Basin of southern Utah and northern Arizona. One site has been heavily grazed yearlong for about 100 years; the second has been lightly to moderately grazed in winter for 3 years; the third has had 10 years of recovery from heavy grazing; and the fourth is a relic, ungrazed blackbrush ecosystem. Soils were 87 to 99% sand and gravel with mean pH's 8.2 to 8.5. The relic site had significantly more herbaceous vegetation cover (composed primarily of perennial grasses) and total cover than all other sites. The relic site also had significantly more shrub and cryptogamic cover than the heavily grazed and recovery sites. The recovering site showed no significant differences than the heavily grazed site for any of the measured parameters.
    • A Model for Assessing Investments in Intensive Grazing Technology

      Wilson, P. N.; Ray, D. E.; Ruyle, G. B. (Society for Range Management, 1987-09-01)
      The financial profitability of intensive grazing management techniques such as short duration grazing (SDG) and the Savory Grazing Management (SGM) has received very little attention in the range management or economics literature. Most research has emphasized variables which measure technical rather than economic efficiency. A conceptual economic model is presented which illustrates the importance of the management factor in determining the optimal stocking rate and profitability of cell grazing practices. Empirical results yield internal rates of return on an after-tax basis for a $10,000 grazing cell for 11-40% assuming cow herd productivity is maintained at, or increased above, pre-adoption levels. As cell costs increase and stocking rates increase, ranch profitability declines and increases respectively in almost all cases. The principal determinant of long-run profits is found to be livestock productivity since this factor has a greater impact on profitability than stocking rate levels or cell investment costs. Increased stocking rates with intensive grazing technology do not insure increased profits unless concurrent improvement in range, livestock, and business management practices are adopted.
    • A Rapid Method for Assessing Rates of Soil Erosion from Rangeland: An Example from Botswana

      Abel, N.; Stocking, M. (Society for Range Management, 1987-09-01)
      The erosion of rangeland soils is a widespread problem in Africa. Yet, there are few methods for estimating its rate. Using data from 2 catchments in Botswana, a technique for estimating erosion and sediment yield is demonstrated. It involves low level photographic sampling of vegetation cover, kriging to interpolate percentage cover from sample points, and the application of a simplified soil loss estimation procedure called SLEMSA. This modelling approach gives gross soil loss and allows the estimation of sediment yield. It is easy and cheap to apply and gave results in line with field experience.
    • Forage Maturity Effects on Rumen Fermentation, Fluid Flow, and Intake in Grazing Steers

      Adams, D. C.; Cochran, R. C.; Currie, P. O. (Society for Range Management, 1987-09-01)
      Eight ruminally fistulated steers were observed on native range from 4 May 1981 to 5 Nov. 1981 to determine effects of advancing forage maturity on rumen fermentation, fluid passage, fluid volume, and forage intake. Effects of these factors are poorly defined for cattle on the Northern Great Plains but are essential for developing management strategies for optimum animal production. On 6 different dates, the steers were given an intraruminal dose of cobalt ethylenediaminetetraacetate (CoEDTA), and samples of rumen fluid were drawn at 4-hour intervals over a 24-hour time period. Rumen fluid samples were analyzed for volatile fatty acid, ammonia-N, cobalt concentration, and pH. CoEDTA was used as a marker to estimate rumen fluid passage and volume. Forage intake was determined by total fecal collection and in vitro digestibility of the forage. Total ruminal volatile fatty acid, molar proportions of individual volatile fatty acid, pH, and ammonia-N concentrations varied (P<0.01) within each of the six 24-hour periods, but the changes were dependent on date. Advancing forage maturity was associated with reduction in individual and total ruminal volatile fatty acid, ammonia-N, pH, and fluid dilution rate. Rumen fluid volume increased with increasing forage maturity. Variation in organic matter intake was small (P>0.05) over the range of forage maturities studied. We concluded that variation in rumen fluid passage, volume, and fermentation depended on forage maturity, and protein supplementation may be beneficial during late summer-early fall to increase or sustain animal production.
    • Frequency Sampling and Type II Errors

      Whysong, G. L.; Brady, W. W. (Society for Range Management, 1987-09-01)
      Probabilities of detecting frequency differences based on data obtained by random sampling were determined by computer simulation. Artificial, monotypic populations of known frequency were generated and sampled. Sample sizes of 100, 200, 500, and 1,000 plots were used to compare baseline populations of 20, 50, and 80% frequency to populations having progressively larger or smaller frequencies. Probabilities of detecting a difference in frequency from baseline populations were empirically estimated from 10,000 comparisons using a test of proportions (P<0.05). Results indicated that the power of the test was substantially reduced at lower sample sizes. Equating the probability of Type I and Type II errors at 0.05 resulted in sample sizes of approximately 500 plots being needed to statistically distinguish between differences of plus or minus 10% frequency.
    • Improving Germination Rate of the Florida Legume Galactia Elloittii

      Muir, J. P.; Pitman, W. D. (Society for Range Management, 1987-09-01)
      The perennial legume, Galactia elliottii Nuttal, is widely distributed in the Spodosol soils (flatwoods) of the Southeastern United States and could have potential as a component of plant mixtures for revegetating deteriorated flatwoods rangeland and other disturbed sites. Seeds of this legume were collected from a peninsular Florida flatwoods site as they developed during the fall of 1983. Since a range in seed development was obtained, seeds were grouped according to maturity and fill. Seed treatments as well as seed development effects on germination were evaluated. Seed treatment by seed development interactions were obtained (P<0.05) indicating that seed of the 3 development groups (mature full seed, mature partially filled seed, and green seed) responded differently to the seed treatments. Mechanical scarification with sandpaper and treatment with sulfuric acid effectively increased (P<0.05) both total germination and rate of germination compared to the untreated control for the 2 mature seed groups. Mechanical scarification and sulfuric acid treatment also increased rate of germination of green seed. However, final (day 52) total germination of sandpaper-scarified green seed did not differ (P>0.05) from the control. Hot water treatment was effective in increasing total germination of green seed but did not produce a response (P<0.05) until after the first week of incubation. Mature seeds from a number of sites were collected in the winter of 1986-87 and composited for germination studies. Sandpaper scarification, sulfuric acid, and a control were evaluated. Initial germination of 84% for sandpaper-scarified seeds from this trial was greater than germination of similar seeds from 1983, while sulfuric acid-treated seeds did not germinate as well. Effectiveness of mechanical seed coat disruption at increasing germination of mature seed indicates that the primary limitation to germination of mature seed of this legume is seed coat impermeability. Differential responses among seed of differing development indicates that seed fill occurred in the green seed before complete development of seed coat impermeability, thus, allowing less severe treatments than seed coat disruption to affect germination.