• Contrasts of esophageal-fistula versus bite-count techniques to determine cattle diets

      Ortega, I. M.; Bryant, F. C.; Drawe, D. L. (Society for Range Management, 1995-11-01)
      To understand how different techniques might affect diet estimates for cattle, the esophageal-fistula and bite-count techniques were compared using trained cattle. For the Texas Coastal Bend, bite-count was not as reliable a technique as the esophageal fistula. These techniques differed in estimation of forage classes and plant species in cattle diets. The esophageal-fistula technique was more accurate however, the bite-count technique may be acceptable if analyses are limited to only those plant species making up >2% of the diet.
    • Ecosystem changes associated with grazing intensity on the Punta Ninfas rangelands of Patagonia, Argentina

      Beeskow, A. M.; Ellisalde, N. O.; Rostagno, C. M. (Society for Range Management, 1995-11-01)
      Changes in the vegetation and soil surface were assessed along a grazing intensity gradient on rangelands of the Punta Ninfas area in southern Argentina. Thirty-two transects were sampled in areas with different grazing intensity. Bray-Curtis polar ordination and simple correlation were used to display changes in community composition and measure association between different community attributes. The first axis expressed the changes in species composition along a gradient of grazing intensity. The extremes of the gradient were represented by shrub and grass steppes. Shrub steppes dominated in heavily grazed areas close to permanent water points, while grass steppes dominated in lightly grazed areas in the extremes of the paddocks. A significant negative relation (r = -0.81, P<0.05) between grass and shrub cover suggested that grasses decreased as shrub increased. Flechilla (Stipa tenuis Phil.) and fiechilla negra [Piptochaefirrm napostaense Speg.) Hackel ap Stuckert.] were the main decreaser grasses while quilembai (Chuquiruga avellanedue Cav.) was the main shrub invading the grass steppes. Uneroded soil surface conditions decreased, and the size and frequency of crusted and desert pavement areas and mounds increased with shrub cover. Three states or stages of range degradation were identified along the gradient of grazing intensity. Grass steppe represented the most desirable state in term of livestock production and soil stability, while shrub steppe represented the most degraded and least productive state.
    • Forage quality, intake, and digestibility of year-long pastures for steers

      Kloppenburg, P. B.; Kiesling, H. E.; Kirksey, R. E.; Donart, G. B. (Society for Range Management, 1995-11-01)
      Thirty-six weanling steer calves (avg wt = 174 +/- 14 kg) were grazed on either wheat, irrigated improved, or native rangeland pastures from December 1989 to December 1990. Irrigated improved pastures consisted of 2 cool-season [tall wheatgrass [Agropyron elongatum (Host.) Beauv.], tall fescue (Festuca arundinacea Schreb.) 2 warm-season [bermudagrass (Cynodon dactylon (L.) Pers.], bluestem (Bothriochloa ischaemum Keng.), and annual wheat. Wheat pastures were grazed from 13 December to 11 April. Warm-season pastures were grazed from 30 May (bermudagrass) or 27 June (bluestem) until 3 October. Cool-season pastures were grazed at other days during spring and fall seasons. Rumen evacuation procedures were used to evaluate forage quality and estimate forage intake during each grazing season. Winter rangeland pastures were lower in nutritional quality (based on protein and fiber contents) and in vitro organic matter digestibility (53 vs 85%, P < 0.05) compared to wheat pasture. During spring, rangeland pastures were still lower in protein and higher in fiber but in vitro organic matter digestibility (72, 73, 72%; respectively, for wheatgrass, fescue and rangeland) was similar (P = 0.70) for all forages. Rangeland and warm-season pastures were similar in quality during summer but rangeland pastures were higher (P< 0.10) in in vitro organic matter digestibility (65, 69, and 73%; respectively, for bermudagrass, bluestem, and rangeland). Rangeland pastures were again lower in quality and digestibility than cool-season grasses during the fall. There were no difference (P>0.10) in organic matter intake (% of body weight) during winter, summer, and fall season but during spring organic matter intake was greater (P < 0.10) for steers on rangeland pasture than for those on cool-season grasses.
    • Genetic aspects of diet selection in the Chihuahuan desert

      Winder, J. A.; Walker, D. A.; Bailey, C. C. (Society for Range Management, 1995-11-01)
      Fecal microhistology and chemistry were used to evaluate botanical composition and quality of diets selected by Brangus cattle grazing Chihuahuan desert range in 3 seasons; fall: October, 1991; winter: January, 1992; and summer: July, 1992. Fecal samples were collected from 100 head in fall (58 2-8 year cows and 42 calves), 53 head (2-8 year-old cows) in winter, and 44 head (2-8 year-old cows) in summer. Paternal half sib analyses were used to estimate genetic and phenotypic variances and heritability estimates. Heritability is the proportion of total (phenotypic) variation which is due to additive genetic effects. The effect of sire within age was observed for percentage of Aristida spp. (P= 0.01), Sporobolus spp. (P= 0.09), total grasses (P = 0.02), Croton pottsii (Klotzsch) Muell.-Arg. (P= 0.03), and total forbs (P =0.02) in fall diets. The number of grass species in diets was also affected by sire (P=0.03). Heritability estimates were 0.87, 0.51, 0.78, 0.76, and 0.79 for percentages of Aristida spp., Sporobolus spp., total grasses, Croton pottsii, and total forbs, respectively. Heritability estimates for number of grass and forb species in fall diets were 0.68 and 0.26, respectively. Heritability estimates for winter samples were 0.40, 0.00, 0.37, and 0.27 for percentages of Sporobolus spp., total grasses, Yucca elata Engelm., and total shrubs, respectively. Heritability estimates for the number of grass and total species observed in winter diets were 1.11 and 0.47, respectively. Heritability estimates for percentages of Bouteloua spp., total grasses, Croton pottsii, Dalea spp., and total forbs in summer samples were 0.20, 0.55, 0.58, and 0.46, respectively. Heritability estimates for the number of grass and total species in summer diets were 0.49 and 0.79, respectively. These data suggest that genetic composition of beef cattle may affect diet selection under Chihuahuan desert conditions.
    • Grazing effects on soil water in Alberta foothills fescue grasslands

      Naeth, M. A.; Chanasyk, D. S. (Society for Range Management, 1995-11-01)
      Grazing can have a profound impact on soil water through its influence on infiltration via treading and on evapotranspiration through defoliation. Hydrologic changes in rangelands are most often associated with heavy grazing intensities although these changes do not increase linearly with grazing intensity. The objectives of this study were to quantify the impacts of grazing on the soil water regimes of sloped areas of the foothills fescue grasslands of Alberta. The study site was located at the Agriculture Canada Research Station at Stavely, Alberta. The effects of 2 grazing intensities (heavy = 2.4 AUM ha-1 and very heavy =4.8 AUM ha-1) for 2 grazing treatments (short duration = 1 week in mid-June and continuous grazing = May through October) were compared to an ungrazed control. The study was initiated in June 1988 and ended in April 1991. Surface soil water and soil water with depth were measured throughout each growing season using a neutron probe. Surface soil water (0 to 7.5 cm) across slope positions was lowest in the control and highest in the continuous very heavy treatments, but the trend in profile soil water (to 50 cm) was the opposite. Total profile soil water in the short duration very heavy treatment was greater than that in the continuous very heavy treatment, while soil water in the short duration heavy treatment was similar to that in the continuous heavy treatment. Vegetation at the study site was regularly water-stressed, as evidenced by soil water that was often below permanent wilting point, generally by mid-summer each year. Soil was near or below permanent wilting point in the autumn, regardless of its status throughout the growing season. Profile soil water was similar across treatments in autumn, indicating vegetation is using all available soil water. In contrast, soil water was generally near or above field capacity every spring, indicating the importance of snowmelt infiltration in these ecosystems. Only major (greater than 75 mm) summer rainstorms recharged soil water to field capacity. Thus it is concluded that maintenance of a vegetative cover that will trap snow for potential snowmelt infiltration is critical to soil water recharge of these ecosystems. Any grazing management regime that enhances litter accumulation and carryover should facilitate such snowmelt soil water recharge.
    • Invasive potential of ashe juniper after mechanical disturbance

      Owens, M. K.; Schliesing, T. G. (Society for Range Management, 1995-11-01)
      Reinvasion of mechanically disturbed juniper communities is possible through contributions from the soil seedbank, seed rain, and the juvenile seedling bank. We compared spatial distribution of the seedbank and seed rain of undisturbed communities to sites where trees were deliberately left as single trees, small mottes of less than 5 trees per group, or large mottes of 5-10 trees per group. Seed density in the litter layer ranged from 1,197 to 1,436 seeds m-2 and in the soil layer from 318 to 617 seeds m-2. Seed rain ranged from 275 to 366 seeds m-2 over all tree arrangements. The treatment associated with single trees caused the litter layer to be removed resulting in the removal of that portion of the seedbank, consequently most seeds (>80%) were found under the canopy of mature, seed-producing trees. Soil disturbance was less severe in small and large motte arrangements, so only 65% of the soil seed bank was under mature trees. In undisturbed communities, the seed population was distributed evenly under tree canopies and in interspaces. Viability and germinability within the seedbank were low (4% and 0%, respectively). Viability of new seed was 47% and germinability was approximately 5%. The juvenile seedling bank contained a sufficient number of seedlings (408 seedlings ha-1) for ashe juniper to regain dominance on the site through growth. There was no advantage to any spatial pattern of tree distribution in terms of invasive potential when fewer than 10 trees ha-1 were left on a site. However, when 20-50 trees ha-1 are left on a site, tree spatial arrangement has a significant effect on reinvasion rates.
    • Mountain big sagebrush browse decreases dry matter intake, digestibility, and nutritive quality of sheep diets

      Ngugi, R. K.; Hinds, F. C.; Powell, J. (Society for Range Management, 1995-11-01)
      A metabolism study evaluated the influence of increasing quantities (0-30% dry matter basis) of mountain big sagebrush (Artemisia tridentata ssp. vaseyana Rydb. Beetle) on dry matter intake and in vivo digestibility of wether diets. Diets consisted of hand-harvested, coarse-ground and frozen current year's growth of mountain big sagebrush leaves and twig tips mixed with chopped native grass hay. Dry matter intake decreased from 93 to 23 g dry matter day-1 kg metabolic weight-1 and in vivo dry matter digestibility from 59 to 0% with increasing levels of sagebrush in the diet. With increasing levels of sagebrush in the diet, water, lignin, and nitrogen contents increased in the diet, but decreased in the dung, while fiber components decreased in both the diet and dung. Total nitrogen intake decreased from 1.58+/-0.041 to 0.406+/-0.070 g day-1 kg metabolic weight-1, and nitrogen retention decreased from 0.80 g day-1 kg metabolic weight-1 with no sagebrush to a slight loss of nitrogen with 30% sagebrush in the diet. Mountain big sagebrush was not readily consumed by wethers when fed together with grass; as low as 10% sagebrush in the diet seems to adversely influence intake and digestibility. Therefore, when other more favorable forages are not available, sheep and other ruminants with similar physiological responses to mountain big sagebrush may not meet their nutrient requirements through increased sagebrush consumption.
    • Observations on spread and fragmentation of blue grama clones in disturbed rangeland

      Samuel, M. J.; Hart, R. H. (Society for Range Management, 1995-11-01)
      Establishment of blue grama (Bouteloua gracilis [H.B.K.] Lag ex. Steud.) depends on adequate precipitation at critical times and on reduced competition from associated vegetation. These conditions rarely occur on Central Plains rangelands. Therefore, rapid vegetative spread of new seedlings is desirable for colonizing disturbed rangeland. Blue grama genotypes selected for rapid spread would also be desirable for rangeland seeding. For 6 years, we followed the rate of spread of 19 blue grama clones originating from seedlings which emerged in 1980 and grew under natural competition. We observed a 4.5-fold difference in basal area and a 16.3-fold difference in above-ground biomass of these clones, perhaps because of genetic differences among clones and varying levels of competition. Clones must be tested under uniform competition with clonal replication to obtain reliable estimates of their capacity to spread.
    • Phosphorus supplementation of replacement heifers in the Northern Great Plains

      Karn, J. F. (Society for Range Management, 1995-11-01)
      Studies were initiated in 1980 and 1984 to compare animal performance, dietary P levels, and serum mineral levels of P supplemented and unsupplemented replacement beef heifers (Bos taurus). Phosphorus supplementation levels averaged 4 g day-1 from 14 November 1980 and 24 January 1984, respectively, until 1 September 1980 and 15 October 1984, respectively, when supplemental P was raised to 6 g day-1. Heifers in both studies received mixed hay, primarily smooth bromegrass (Bromus inermis Leyss.), and rolled oats during their first winter and hay only the second winter. During the summer they grazed on native pastures which contained primarily western wheatgrass (Pascopyrum smithii (Rydb.) A. Love), needleandthread (Stipa comata Trin. and Rupr.), green needlegrass (S. viridula Trin.), blue grama (Bouteloua gracilis (H.B.K.) Griffiths), and upland sedges (Carex spp.). Hereford and Hereford-Angus cross heifers in the first study showed no weight gain or serum P response to supplemental P, but conception rate over the 2 studies was lower (P<0.05) for the unsupplemented heifers and 75% of the open heifers occurred in the first study. Hereford-Simmental heifers used in the second study demonstrated an immediate weight gain response (P<0.06) to supplemental P which persisted to the end of the study in 1985, but there was only 1 open heifer in the unsupplemented group in this study, compared to 3 in the first study. Serum P was higher (P<0.06) for P supplemented than control heifers only when they were removed from summer pasture in the second study. Diet P (2.10 g kg-1) for unsupplemented Hereford-Simmental heifers during the winter of 1984 was mar- ginal, but diet P (2.53 g kg-1) for unsupplemented Hereford and Hereford-Angus heifers during the winter of 1980-1981 was clearly above recommended levels. Modest weight gain differences in the second study, serum P data and differences in conception rate suggest that Northern Great Plains forages are marginal to deficient in P for replacement beef heifers, but P supplementation would be expected to produce small and variable benefits
    • Plant response to soils, site preparation, and initial pine planting density

      Pearson, H. A.; Wolters, G. L.; Thill, R. E.; Martin, A.; Baldwin, V. C. (Society for Range Management, 1995-11-01)
      This study described the effects of soils, site preparation, and initial pine regeneration spacings on tree growth and the associated understory woody and herbaceous plant succession. Although Sawyer soils appeared more productive than Ruston soils before the harvest and regeneration treatments, woody and herbaceous plant differences were not apparent between the soils after regeneration. During the first 3 years after treatment, the mechanical site preparation method (shear-windrow-burn) reduced woody plant heights more than the underplant-release method; however, these height differences disappeared by the 6th year of post-treatment. Woody plant densities decreased initially, increased by the 6th year after treatment, and decreased to pretreatment levels by the 10th year. Herbage yields increased significantly after site preparation and pine regeneration through the 3rd year, decreased by the 6th year, and declined to levels below pretreatment by the 10th year. initial pine planting densities did not significantly influence the understory herbage yields during the first 10 years as a result of the confounding effects of the other woody plant growth.
    • Rainwater harvesting for increasing livestock forage on arid rangelands of Pakistan

      Suleman, S.; Wood, M. K.; Shah, B. H.; Murray, L. (Society for Range Management, 1995-11-01)
      This study determined forage production and cover of several plant species resulting from the use of water harvesting catchments with catchment: cultivated area ratios of 1:1 and 1.25:1 and contributing aprons with 7, 10, and 15% slope gradients. Plots with 1.25:1 ratios produced more forage and had more cover than plots with 1:1 and 0:1 ratios. Plots with 7, 10, and 15% slope gradients had similar forage production and cover. Tuft planted plots produced more forage and cover than seeded plots. Ghorka (Elionurus hirsutus (Vahl) Munro), blue panicum (Panicum antidotale Retz.), and buffer (Cenchrus ciliaris L.) grasses produced similar forage and cover, which was higher than khev grass (Sporobolus helvolus (Trin.) Th. Dur. & Schinz) production and cover.
    • Relative abundance and diet composition of Chacoan cavies in relation to range condition

      Rosati, V. R.; Bucher, E. H. (Society for Range Management, 1995-11-01)
      The relative abundance and dietary botanical composition of the Chacoan cavy (Pediolagus salinicola) was studied on sites of very good, good, and poor range condition in the Western Chaco, Argentina. Pellet count data showed that Chacoan cavy densities varied (P<0.001) among these areas. In both seasons, the highest number of pellets was found in the area of poor condition. This area was characterized by an absence of grasses, dense cover of a creeping fern (Selaginella sellowii), thorny shrubs and a scarcity of dicot herbs. In contrast, a decrease (P<0.05) in Chacoan cavy densities was found in the good and very good range condition areas, coincident with the increase of grass and forb cover. Fecal analysis showed that Chacoan cavy diets were greatly influenced by the amount of forage available, which varied according to the condition of the rangeland. Forbs were the main forage class consumed in all range conditions, but the species composition differed among condition classes. For example, several species of dicot forbs were consumed in areas of very good and good range condition, but Selaginella sellowii was the main dietary forb when the range condition was poor. We concluded that range condition affected the relative abundance and diet of Chacoan cavies of Western Chaco, Argentina. High Chacoan cavy density should be considered as an indicator of vegetation depletion caused by other factors rather than a primary cause of savanna degradation.
    • Response to comment: Ungulate herbivory on willows on Yellowstone's northern winter range

      Singer, F. S.; Cates, R. G. (Society for Range Management, 1995-11-01)
    • Technical Note: Datalogger control of environmental chambers for variable-temperature germination experiments

      Hardegree, S. P.; Burgess, M. D. (Society for Range Management, 1995-11-01)
      Environmental conditions in the seedbed are much more variable than have historically been simulated in laboratory germination experiments. This paper describes a laboratory control system for real-time simulation of seedbed temperature regimes. The system is composed of a set of small refrigerators that have been enhanced with incandescent and fluorescent lights, fans and electrical-resistance heaters. The germination chambers are regulated by an electronic data acquisition/control system that allows each chamber to vary internal temperature on a continuous basis. Field temperatures can be transmitted to the laboratory and the germination chambers programmed in near-real-time for simultaneous laboratory germination/field emergence studies.
    • Technical Note: Effect of substrate drying method on in vitro dry matter disappearance in moose

      Faber, W. E.; Pehrson, Å.; Jordan, P. A. (Society for Range Management, 1995-11-01)
      One identified potential source of error in nutritional evaluations using the in vitro technique is the drying method used on test substrates. This study was conducted to determine what effect, if any, different drying methods have on the dry matter disappearance of 4 browse species in moose (Alces alces L.) inoculum. Browse species were Scots pine (Pinus sylvestris L.), birch (Betula pendula Roth, Betula pubescens Ehrh.), willow (Salix spp.), and sweetgale (Myrica gale L.). In addition, we determined the effects of drying method on neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) concentration of the browse species. Each species was either freeze-dried (-40 degrees C) or oven-dried at 35 degrees, 60 degrees and 105 degrees C, respectively. High drying temperatures significantly depressed (P<0.0001) in vitro dry matter disappearance (WDMD) in all browse species tested except of Scats pine. High temperatures also reduced NDF (P<0.05) in all the species, while ADF and ADL were elevated (P<0.05) in all specks except Scats pine. We conclude that freeze-drying is the most preferable method to be used on forage and browse samples being evaluated for nutritional quality.
    • Technical Note: Root-plowing effects on nutritional value of browse and mast in south Texas

      Ruthven, D. C.; Hellgren, E. C. (Society for Range Management, 1995-11-01)
      Leaf and mast material was collected from mesquite (Prosopis glandulosa Torr.), huisache (Acacia smallii Isely), granjeno (Celtis pallida Torr.), and hog plum (Colubrina texana (T.& G.) Gray) on both root-plowed and untreated sites in south Texas. Forages were analyzed for nitrogen (N), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD). Forages differed among species for N, NDF, and IVDMD. Leaf IVDMD of huisache and hog plum was higher on untreated sites. Huisache mast was higher in N and NDF concentrations, but not IVDMD, on untreated sites. Browsers on root-plowed sites may be forced to use forages of fewer digestible nutrients than on untreated sites. The cause of changes in browse quality following brush manipulation should be examined.
    • Water erosion prediction project (WEPP) rangeland hydrology component evaluation on a Texas range site

      Savabi, M. R.; Rawls, W. J.; Knight, R. W. (Society for Range Management, 1995-11-01)
      The USDA-Water Erosion Prediction Project (WEPP) is a new technology based on the fundamentals of hydrology, soil physics, plant science, hydraulics, and erosion mechanics. WEPP hydrology includes simulation of excess rainfall using the Green and Ampt infiltration equation, surface runoff routing, evapotranspiration, percolation, and surface drainage. Hydrometeorological, soil, topography, and vegetation data from a range in Texas were used to test the WEPP rangeland hydrology model. Measured surface runoff and root zone soil water content from the site were compared with the simulated results of the WEPP model. The results indicate that the WEPP model (version 93.0) is capable of simulating soil water content and storm runoff. The Nash and Sutcliffe coefficient, NSR, between measured and simulated root zone soil water content and storm runoff was .88 and .84, respectively, for the bare ground plots. However, for the plots with herbaceous vegetation the discrepancy between model simulated storm runoff and soil water content was more than expected (NSR = .46 and NSR = .53, respectively).