• 14- Vs. 42-Paddock Rotational Grazing: Forage Quality

      Heitschmidt, R. K.; Dowhower, S. L.; Walker, J. W. (Society for Range Management, 1987-07-01)
      Research was initiated at the Texas Experimental Ranch in 1981 to quantify the effects of 2 livestock densities on forage quality in a rotational grazing (RG) treatment. Livestock densities evaluated were equivalent to 14 and 42-paddock RG treatments. Baseline data were collected in 1981 from 3 adjacent 30-ha paddocks in a 465-ha, 14-paddock, cell designed RG treatment stocked at a rate of 3.6 ha/cow/year. Near the beginning of the 1982 growing season the center paddock was subdivided into three, 10-ha paddocks to establish the RG-42 treatment. Herbage standing crop was harvested before and after each grazing event during the 40-month period, separated by species or species group into live and dead tissue, and each fraction analyzed for percentage crude protein (CP) and organic matter digestibility (OMD). Livestock density had minimial effect on forage quality. Live tissue was of higher quality than senesced tissue regardless of plant species. Increases and decreases in overall quality during grazing periods were positively associated with rates of plant growth. Number of periods when forage quality increased or decreased during grazing and magnitude of change were unaffected by treatment. Lack of significant treatment effects on forage quality is attributed to the general absence of significant treatment effects on forage production, species composition, and live/dead ratios.
    • A Dynamic Programming Application for Short-Term Grazing Management Decisions

      Rodriguez, A.; Roath, L. R. (Society for Range Management, 1987-07-01)
      This study emphasizes short-term management decisions that are made in a yearling cattle operation in northeastern Colorado. Empirical equations describing forage and animal growth were coupled with marketing and supplementation alternatives. Four cases were modeled with high and low stocking densities and partial or total sales strategies. Net present value of yearling steer sales were maximized using dynamic programming. Early sale of cattle was an economically favorable alternative because of decreasing daily gains toward the end of the grazing season (September-October) and decreasing steer prices. Supplementation during September-October was also profitable to offset the decreasing trend in average daily gain caused by declining forage quality. Under the high stocking density and partial sales strategy, early sales regulated standing crop left at the end of the grazing season. Under the low stocking density and partial sales strategy, early sales partially offset net return losses for those animals that had to be sold at the traditional marketing date. The total sales strategy favored sales of livestock 2 weeks before traditional marketing under low and high stocking density and partial sales strategy. Net present values per pasture were slightly larger for the total sales strategy than the partial sales strategy using both low and high stocking densities.
    • A New Sticky Trap for Monitoring Seed Rain in Grasslands

      Huenneke, L. F.; Graham, C. (Society for Range Management, 1987-07-01)
      The use of an inexpensive, commercially available device as a sticky trap for capturing dispersing seeds in the field is described. Trap performance in capturing seeds under various conditions is evaluated. The traps perform well in capturing small, lightweight seeds, particularly those with awns or ornamentation, as would be typical of many grassland plant species. The adhesive surface of the traps retains its effectiveness when moist, and in the hot, dusty conditions of the field. However, the traps have poor rates of capture for certain seed types, and for seeds dropped from considerable heights. These limitations of performance, which are probably shared with other types of sticky traps for seeds, must be considered when sticky traps are used to evaluate seed rain.
    • Allelopathic Effects of Kochia on Blue Grama

      Karachi, M.; Pieper, R. D. (Society for Range Management, 1987-07-01)
      The allelopathic effects of kochia aqueous extracts found in kochia (Kochia scoparia L. Roth.) on seed germination and seedling growth of blue grama (Bouteloua gracilis [H.B.K.] Lag.) were studied in laboratory experiments. Extracts were from regrowth, whole tops, leaves, and stems, representing the vegetative and reproductive phenologies. Inhibition of seed germination did not occur. However, seedling radicle and shoot growth were significantly (P<0.05) affected. Inhibition declined significantly with concentrations of the solutions and advancing phenological stage. Similarly, hot water extracts inhibited growth more than cold water extracts. The data suggest possible inhibitory effects of kochia litter under field conditions, but detailed studies are lacking.
    • An Updated Procedure for Cecal Cannulation in Sheep and Cattle

      Caton, J. S.; Krysl, L. J.; Freeman, A. S.; Ruttle, J. L.; Branine, M. E. (Society for Range Management, 1987-07-01)
      Fifteen cattle (236-500 kg) and 38 sheep (36-55 kg) were fitted with 2 types of indwelling cecal cannulae. Cannulae were made of either clear silicone or plastic tubing. The surgery was conducted in a one-step procedure that involved pharmaceuticals and equipment that were readily available. Results indicated a success rate of 67% (33% failure due to inability to locate the cecum at the time of surgery) in cattle and 100% in sheep. Both cannula types tested were acceptable, but the cannula made from plastic tubing was more desirable because it was less bulky, more durable, and easier to construct. Animals fitted with cecal cannulae appeared to be healthy and to have normal life spans.
    • Application of Herbicides on Rangelands with a Carpeted Roller: Timing of Treatment in Dense Stands of Honey Mesquite

      Mayeux, H. S. (Society for Range Management, 1987-07-01)
      Several herbicides were evaluated for control of honey mesquite (Prosopis glandulosa Torr.) when applied with a tractor-mounted carpeted roller. Experiments were placed in stands with relatively high honey mesquite densities (2,850 to 4,930 plants/ha). An ester of 2,4,5-T was ineffective at concentrations ranging from 3 to 240 g/L when applied monthly from April through September. Equal-ratio mixtures of 2,4,5-T and picloram provided up to 80% mortality (root-kill) when applied at a total concentration of 24 g/L in June, but did not control honey mesquite if applied in September. Mortality obtained with picloram applied alone in June as a 12 g/L solution varied with year and location from 42 to 61%. Picloram provided 61 to 91% mortality at a concentration of 60 g/L when applied in June, and up to 99% mortality when applied as a 120 g/L solution. Picloram was highly effective when applied in July and August in a year of favorable growing conditions, providing 94 and 96% mortality as 60 g/L solutions, respectively. Mortality was reduced to a maximum of 79% when picloram was applied from April through September in a drought year. Clopyralid and a 1:1 mixture of picloram and clopyralid were usually equal or superior to picloram in effectiveness.
    • Cattle Grazing White Locoweed: Diet Selection Patterns of Native and Introduced Cattle

      Ralphs, M. H.; Mickelsen, L. V.; Turner, D. L. (Society for Range Management, 1987-07-01)
      Cattle preference for immature white locoweed (Oxytropis sericea Nutt.) seed pods reported in a previous intensive grazing study was confirmed using free-ranging cows under natural grazing conditions. Diets were quantified by bite count. The succulent immature seed pod was palatable and preferentially selected until its supply was exhausted. Locoweed flowers or mature seed pods were not grazed and very few locoweed leaves were consumed. Native cows (born and raised on the range) and introduced 2-year-old replacement heifers (raised in another part of the state with no prior grazing experience with locoweed) consumed similar amounts of locoweed pods.
    • Cattle Grazing White Locoweed: Influence of Grazing Pressure and Palatability Associated with Phenological Growth Stage

      Ralphs, M. H. (Society for Range Management, 1987-07-01)
      Understanding the conditions in which livestock consume poisonous plants is necessary to develop management strategies to reduce losses. Three 10-day grazing trials were conducted to observe consumption of white locoweed (Oxytropis sericea Nutt.) by cattle. The trials corresponded to the phenological growth stages of white locoweed: (1) flower; (2) immature seed pod; and (3) mature seed pod/seed shatter. Six esophageally fistulated Hereford steers were used to collect diet samples. In trial 1, steers selected the locoweed flower only when supplies of grass and other forbs were depleted. In trial 2, steers voluntarily selected the immature pod, which comprised 50% of their diet by the middle of the trial. There was very little consumption of locoweed in trial 3. Few locoweed leaves were consumed throughout the experiment. Immature locoweed pods were palatable and readily selected by cattle. By restricting access at the immature pod growth stage and insuring adequate forage is available at other times, cattle consumption of white locoweed on this site should be minimized.
    • Diet and Forage Intake of Cattle on Desert Grassland Range

      Hakkila, M. D.; Holechek, J. L.; Wallace, J. D.; Anderson, D. M.; Cardenas, M. (Society for Range Management, 1987-07-01)
      Cattle production on desert grassland ranges in southern New Mexico has been low, although limited research shows diet nutritional quality of cattle is adequate to meet production needs during most seasons. Forage intake data are lacking for cattle on desert grassland ranges. Five esophageal-fistulated steers were used to evaluate diet quality and botanical composition on desert grassland range in southern New Mexico. Another 6 steers were used to collect feces to determine intake. Cattle changed their diet with seasonal advance to maximize diet quality. Crude protein concentrations of cattle diets were well above those needed for lactation and daily gain during spring and summer. Diet samples were high in neutral detergent fiber (66-81%), suggesting low energy in the forage. Low forage intake was the main nutritional constraint identified. Even during the summer growing season, organic matter intake never exceeded 1.5% of body weight. We speculate low intakes may have resulted from high summer temperatures that reduced grazing time. During the late fall and winter, low forage quality appears to explain suppressed intake. Protein supplementation in late fall and winter, and energy supplementation in spring, should be advantageous. We caution that data on diet quality without information on forage intake may poorly describe nutritional status of range cattle.
    • Economic Returns from Treating Sand Shinnery Oak with Tebuthiuron in West Texas

      Ethridge, D. E.; Pettit, R. D.; Neal, T. J.; Jones, V. E. (Society for Range Management, 1987-07-01)
      Net returns from control of sand shinnery oak (Quercus havardii) with tebuthiuron [N-(5-1,1-dimethylethyl 1,3,4,-thiadiazol-2-yl)-N, N′-dimethylurea] were evaluated for Southern High Plains ranges. A forage yield function was estimated with regression using 5 years of herbage yield data from the region. The present value of production was determined for 3 calf prices, 3 discount rates, and 4 tebuthiuron treatment rates. Discounted net returns were generally positive with high and moderate calf prices and low and moderate discount rates. The optimum tebuthiuron treatment rate varies with calf prices, discount rate, and treatment cost.
    • Ecotypic Variation in Selected Fourwing Saltbush Populations in Western Texas

      Petersen, J. L.; Ueckert, D. N.; Potter, R. L.; Huston, J. E. (Society for Range Management, 1987-07-01)
      Fourwing saltbush [Atriplex canescens (Pursh) Nutt.] seedlings from 4 western Texas tetraploid populations were established in uniform nurseries at San Angelo, Barnhart, and Marfa, Texas, in 1981 to determine relative adaptability to these respective environments. Survival and canopy development of the ecotypes were similar at the site with the most favorable growing conditions (San Angelo), but the ecotype originating nearest the planting site tended to have greatest survival and canopy size where site conditions were less favorable. Additional shrub attributes evaluated at the San Angelo site included: leaf, current year's stem, and wood phytomass, seasonal nutrient concentrations, and floral development and phenotype. Prediction equations utilizing plant canopy measurements were used to estimate weights of plant components. Variation in canopy size and yields among individual plants within ecotypes masked detection of significant (P lesser than or equal to 0.05) differences among ecotypes, but ecotypes from arid environments tended to be larger and to have greater yields than those from more mesic environments. Concentrations of crude protein (CP), phosphorus (P), and digestible organic matter (DOM) of leaves and stems were similar among the 4 ecotypes. Floral development of the ecotype from the most mesic environment progressed at a faster rate than that of ecotypes from more xeric environments. Ecotypes from xeric environments tended to have fewer staminate plants, but more plants with no sex expression than ecotypes from more mesic areas.
    • Estimating Shrub Production from Plant Dimensions

      Hughes, H. G.; Varner, L. W.; Blankenship, L. H. (Society for Range Management, 1987-07-01)
      Relationships between current season plant production and plant measurements (crown width and volume) were investigated for 4 South Texas shrubs collected during July, 1978. Shrubs investigated were blackbrush (Acacia rigidula), guajillo (A. berlandieri), shrubby blue sage (Salvia ballotaeflora), and kidneywood (Eysenhardtia texana). Regressions of production available to white-tailed deer on both crown width and crown volume yielded coefficients of determination of 25-97%. Log-log and quadratic equations provided better results than linear, logarithmic, or exponential equations. One plant measurement (maximum crown width as an independent variable) produced results comparable to those from crown volume. Range site (sandy loam or gray sandy loam) did not affect plant production:plant measurements relationships, but mechanical treatment (shredding) did. Selecting plants representing the full range of shrub shapes and sizes is critical to the proper use of this method, and treatments which greatly modify plant form will probably require regression equations separate from those for undisturbed vegetation.
    • Modeling Variation in Range Calf Growth Under Conditions of Environmental Uncertainty

      VanTassell, L. W.; Heitschmidt, R. K.; Conner, J. R. (Society for Range Management, 1987-07-01)
      Functional relationships between calf weights and various managerial and environmental factors were developed using 19 years of performance data from 8 cow-calf herds at the Texas Experimental Ranch. Six models were developed to estimate weights at (1) the first weighing at approximately 75 days of age, (2) the second weighing at approximately 152 days of age, (3) the second weighing, using the first weight as a dependent variable, (4) weaning at approximately 237 days of age, (5) weaning, using the first weight as a dependent variable, and (6) weaning, using the second weight as a dependent variable. R2 values for the equations were .79, .83, .90, .84, .89, and .89, respectively. Equations were functions of the grazing treatment (heavy continuous vs. moderate continuous vs. rotational grazing), level of winter supplementation, age of calf at weighing, crossbreeding, linear and quadratic accumulated production year precipitation, and winter/spring temperatures. Performance of the equations was examined by stochastically simulating them for 360 iterations using 36 years of historical precipitation.
    • Nitrogen and Carbohydrate Partitioning in 'Caucasian' and 'WW-Spar' Old World Bluestems

      Coyne, B. I.; Bradford, J. A. (Society for Range Management, 1987-07-01)
      Total nonstructural carbohydrates (TNC) and nitrogen (N) in 'WW-Spar' (Bothriochloa ischaemum) and 'Caucasian' (B. caucasica) Old World bluestems were monitored in field experiments during spring-summer and summer-fall growth cycles. The objectives were to determine seasonal partitioning of TNC and N among biomass compartments and to determine relationships between concentrations and pool sizes of TNC and N in the perennating storage organs (stem bases and roots). Average TNC concentrations during the growing season were highest in the leaf sheaths and enclosed stems followed by leaf blades>stem bases>roots. Total TNC was highest in the roots>stem bases>stem plus sheaths>leaf blades. Average N concentrations were highest in the leaf blades>roots>stems plus sheaths>stem bases while the rank for total N was root>stem base>leaf blade>stems plus sheaths. Thus, the perennating organs (stem bases, roots) represented the largest reservoirs for both TNC and N reserves. Reserve cycles were similar in both grass species. Differences were primarily in the perennating organs as WW-Spar bluestem stored more TNC and N in stem bases and Caucasian bluestem stored more of both constituents in roots It is often assumed that plant vigor is related to TNC and N reserves and that management of forage-based livestock production systems can be keyed to reserve cycles. Therefore, we sought to answer the question of whether concentrations alone could adequately predict relative vigor or whether pool sizes must be known. Our analysis showed that concentrations tracked pool sizes of TNC extremely well in the roots, but that the relationship was not as strong in the stem bases. The relationship for N concentration and total N was highly significant for roots, but not as good as for TNC. Concentrations of N were not good predictors of total N in stem bases. Fluctuations in total N were much greater than for concentration. Although nitrogen-use efficiency increased linearly with season, N investment per unit leaf blade area declined. This suggested that nitrogen limitation was the main cause for reduced rates of increase in TNC-use efficiency during the last third of the first growing cycle. This was a time when TNC investment per unit leaf blade area was increasing. In these Old World bluestems, management decisions related to plant vigor can apparently be keyed to TNC concentrations thereby eliminating the more laborious tasks required to determine TNC pool sizes. Further study is necessary to determine the feasibility and economics of using nitrogen fertilizer applications in the final third of a growing cycle to reverse the loss in leaf TNC-use efficiency observed in this study.
    • Radiometric Reflectance Measurements of Northern Great Plains Rangeland and Crested Wheatgrass Pastures

      Aase, J. K.; Frank, A. B.; Lorenz, R. J. (Society for Range Management, 1987-07-01)
      Calculated reflectance factors and vegetation indices derived from radiometric reflectance measurements were used in regression analyses to test for a single relationship between canopy reflectance characteristics and measured vegetation parameters from 1 moderately grazed and 1 heavily grazed native rangeland pastures and 1 crested wheatgrass [Agropyron desertorum (Fisch. ex Link) J.A. Schultes] pasture. The study was located on a Williams loam (fine-loamy mixed, Typic Argiboroll) near Mandan, North Dakota. Reflectance measurements were made near solar noon once a week during the 1983 and 1984 growing seasons. There was a statistically significant relationship (r=0.76**) between leaf area index and dry green matter among pastures and years. However, each pasture exhibited a unique relationship (statistically significant) between vegetation indices developed from the reflectance measurements and leaf area index or dry green matter. Based on the techniques and wavebands used in this study, over a given geographic region and with pasture management practices known, it may be possible to remotely estimate green dry matter.
    • Responses of Fecal Coliform in Streamwater to Four Grazing Strategies

      Tiedemann, A. R.; Higgins, D. A.; Quigle, Quigley T. M.; Sanderson, H. R.; Marx, D. B. (Society for Range Management, 1987-07-01)
      Concentrations and loadings (output, number day-1 km-2) of fecal coliform (FC) indicator bacteria were measured from 1979 through 1984 in streamflow from 13 forested watersheds under the following range management strategies: (A) no grazing; (B) grazing without management for livestock distribution; (C) grazing with management to obtain livestock distribution, and (D) grazing with management to obtain livestock distribution and cultural practices to increase forage. Both FC concentrations (number/100 ml) and instantaneous loadings differed significantly among strategies, seasons, and water years. Differences among strategies for mean concentrations were A<C=B<D. For instantaneous loadings, significant differences were A<C, B or D; and C<D. FC concentrations were the same for winter and for snowmelt runoff seasons but concentrations of both were significantly lower than during the summer period. Loadings were different for each season with winter<summer<snowmelt runoff. A definite relationship was established between the presence of cattle on the pastures and FC concentrations. Elevated FC counts in strategy D watersheds and loadings in excess of 10^4 organisms day-1 km-2 in the winter season provide evidence that organisms live into and through the winter period in animal feces, sediment, and soil. Results provide evidence that livestock removal may not provide an immediate solution to elevated levels of FC in streamwater.
    • Seasonal Growth Rates of Tallgrass Prairie After Clipping

      Gillen, R. L.; McNew, R. W. (Society for Range Management, 1987-07-01)
      Intensive rotation grazing is dependent on the proper timing of livestock movement for success. The timing of livestock movement is in turn dependent on the rate of forage growth, but quantitative information on growth rates of tallgrass prairie is limited. The objective of this study was to develop information on seasonal growth parameters of tallgrass prairie following uniform clipping. Plots were mowed to 10 cm on various starting dates during the growing season and sampled weekly for live standing crop for 10 weeks following mowing. Four and five regrowth trials were completed in 1984 and 1985, respectively. Regrowth trials were analyzed by fitting second degree polynomial regression models to the weekly standing crop data and calculating several growth parameters from the fitted models. The maximum standing crop of forage regrowth declined significantly as the time of initial clipping was delayed (2,300-280 kg ha-1, 1984; 2,400-1,130 kg ha-1, 1985). The maximum net growth rate also declined significantly with season (52-0 kg ha-1 d-1, 1984; 36-16 kg ha-1 d-1, 1985). The time required to reach maximum regrowth standing crop or maximum net growth rate did not vary significantly with season. If livestock movement under rotation grazing was based strictly on the time to reach maximum net growth rate, the length of the rest period for a given pasture would remain constant or even decrease slightly with season. The attainment of a given level of forage in a pasture as a criterion for livestock movement would result in a better balance between forage livestock production than the use of the time to maximum net growth rate.
    • Soil and Vegetation Responses to Simulated Trampling

      Abdel-Magid, A. H.; Trlica, M. J.; Hart, R. H. (Society for Range Management, 1987-07-01)
      An artificial hoof was used to simulate trampling effects on native shortgrass sods in a greenhouse experiment. Severe to moderate trampling was applied to sods maintained under 3 soil water regimes. Trampling was done either throughout a 32-day period to represent a continuous grazing system, or only during the last 4 of the 32 days to simulate a short-duration grazing system. Soil bulk density increased 3%, and infiltration rate declined 57% under severe trampling. Trampling throughout the 32-day period resulted in 4% higher bulk density than did a similar level of trampling that was applied only during the last 4 days of the trial. Dead vegetation was more easily removed by hoof action than was living vegetation, and severe water stress made plant material more brittle. Aboveground biomass production was 7% greater under trampling that simulated short-duration grazing, and 17% more forage remained in the standing crop under this treatment. About 38% more vegetation was detached by hoof action under simulated continuous grazing as compared with the short-duration grazing treatment.
    • Soil Bulk Density and Water Infiltration as Affected by Grazing Systems

      Abdel-Magid, A. H.; Schuman, G. E.; Hart, R. H. (Society for Range Management, 1987-07-01)
      The influences of continuous, rotationally deferred, and short-duration rotation grazing systems on soil compaction and water infiltration were assessed. Bulk density and water infiltration were measured to evaluate the effects of the 3 grazing systems at moderate and heavy stocking rates. Measurements were made in the spring before grazing and at the end of the grazing season in 1983 and 1984. Bulk density was not affected by grazing systems or stocking rate; bulk density was greater in the fall than in spring of 1984, but not in 1983. Infiltration was significantly lower under the heavy stocking rate than under the moderate stocking rate at the end of the grazing season. The average water infiltration was significantly less in the fall than in the spring for the heavy stocking rate but showed no seasonal effect for the moderate stocking rate. Infiltration was significantly greater under continuous grazing than under rotational deferment but no different from that under short-duration grazing in 1983. However, in 1984 the relationship was reversed. The grazing systems evaluated did not affect soil bulk density and water infiltration in a consistent manner; however, the stocking rate resulted in reduced infiltration during the grazing season.