• Germination response of hand-threshed Lehmann lovegrass seeds

      Hardegree, S. P.; Emmerich, W. E. (Society for Range Management, 1993-05-01)
      Germination of Lehmann lovegrass (Eragrostis lehmanniana Nees) was increased by seed after-ripening and by mechanical scarification of the seed coat. Hand-threshed seeds collected from 5 sites in southern Arizona were periodically germinated over the water potential range of 0 to -1.55 MPa for 98 weeks after harvest. Nonscarified seeds exhibited very low germination at all water potentials for the entire length of the study. Total percent germination of scarified seeds peaked after 34 weeks. Seeds scarified before the after-ripening requirement was met germinated without further scarification at 46 weeks after harvest. Measurements of water uptake rates indicate that seed cost permeability to water contributes little to the increased germinability of scarified seeds.
    • Influence of handling methods on fecal NIRS evaluations

      Pearce, R. A.; Lyons, R. K.; Stuth, J. W. (Society for Range Management, 1993-05-01)
      Experiments were conducted to investigate efficiency in analysis of fecal samples by near infrared reflectance spectroscopy (NIRS) to predict cattle forage diet quality. Stability of fecal samples during shipping and methods of reducing analysis time were evaluated. In experiments with actual and simulated shipping, no difference was found between predictions from samples shipped fresh or frozen, allowing analysis time to be reduced by 1 day. Drying procedures were developed which allowed sample analysis 24 hours after arrival in the lab for an additional reduction of 1 day in analysis time. Minimal effects on NIRS predictions were observed for simulated shipping delays up to 12 days for crude protein and 14 days for digestible organic matter.
    • Influence of rest-rotation cattle grazing on mule deer and elk habitat use in east-central Idaho

      Yeo, J. J.; Peek, J. M.; Wittinger, W. T.; Kvale, C. T. (Society for Range Management, 1993-05-01)
      Elk (Cervus elaphus Linnaeus), mule deer (Odocoileus hemionus Rafinesque), and cattle (Bos taurus Linnaeus) distributions were determined year round from 1975-1979 on a rest-rotation grazing system established in steep mountainous terrain. Following implementation of the grazing system, cattle progressively used higher elevations and steeper slopes in each succeeding year. Elk preferred rested pastures during the grazing season (June-October) and avoided habitat frequented by cattle by using higher elevations and steeper slopes. Few mule deer used the allotment during summer, but during the winter, deer selected habitats grazed previously by cattle. Elk appeared to adjust to the grazing system by making greater use of pastures with cattle present, although preference for pastures without cattle continued.
    • Influence of ruminally dispensed monensin and forage maturity on intake and digestion

      Fredrickson, E. L.; Galyean, M. L.; Branine, M. E.; Sowell, B.; Wallace, J. D. (Society for Range Management, 1993-05-01)
      Eight ruminally cannulated crossbred steers (average weight 336 kg) grazing native blue grama (Bouteloua gracilis [H.B.K.]) rangeland were used in a repeated measures design to evaluate effects of monensin ruminal delivery devices (MRDD) and forage phenology on ruminal digestion. Three periods were assessed: mid-August (Aug.), early October (Oct.), and mid-November (Nov.). One MRDD was placed in the reticulum of 4 steers via the ruminal cannula 21 days before each period. Intake was estimated using total fecal collections. Diet samples were collected using 3 esophageally fistulated steers. Ruminal fill was measured by ruminal evacuation; rate and extent of in situ ruminal neutral detergent fiber disappearance were estimated before ruminal evacuations. Ruminal passage rates, retention time, and apparent total tract organic matter digestibility were estimated using indigestible neutral detergent fiber. In vitro organic matter disappearance of esophageal masticate did not differ (P > .05) in Aug. and Oct. (average of 53.7%), but declined (P < .05) in Nov. (48.7%), whereas organic matter digestibility was greater (P < .10) in Aug. (62.3%) than in either Oct. (55.2%) or Nov. (53.9%). Release of monensin from the bolus (68 mg day-1) was less than expected (100 mg day-1). Intake, organic matter digestibility, ruminal passage rates, retention time, pH, and ammonia were not affected (P > .10) by MRDD. In situ neutral detergent fiber disappearance at 96 hours was decreased (P < .10) by MRDD (68 vs 65% for control and MRDD, respectively). As the grazing season progressed, intake declined (P < .10), whereas ruminal fill and retention time increased (P < .05), and passage rate of indigestible neutral detergent fiber decreased (P < .05). At 48 hours in situ neutral detergent fiber was greatest (P < .05) in Aug. and least (P < .05) in Nov.
    • Nutrient composition of whitetop

      McInnis, M. L.; Larson, L. L.; Miller, R. F. (Society for Range Management, 1993-05-01)
      Whitetop or heart-podded hoary cress (Cardaria draba (L.) Desv.) is an Eurasian native of the Cruciferae actively invading rangelands throughout western North America. The plant is reported to be unpalatable to livestock and contain potentially toxic glucosinolates. Practical experience indicates sheep consume whitetop during its early growth stages and cattle ingest large quantities of seedheads. Chemical analysis of whole plants from rosette to hard seed, respectively, indicated the following trends: crude protein (28.8 to 7.9%), neutral detergent fiber (13.1 to 52.8%), acid detergent fiber (12.0 to 41.8%), cellulose (9.9 to 32.1%), lignin (1.9 to 9.4%), ether extract (1.6 to 2.4%), in vitro organic matter digestibility (77.3 to 49.1%), digestible energy (2.9 to 1.8 Mcal/kg), and total glucosinolates (28.4 to 84.0 micromoles/g). Leaves were higher than stems in crude protein, ether extract, in vitro organic matter digestibility, and digestible energy. Analysis of 11 micro- and macroelements revealed sulfur (S) levels ranged from 0.73 to 2.69% and were therefore higher than the reported maximum tolerable level (0.4%). High S levels likely reflected the S moiety of glucosinolates and their hydrolysis products. Whitetop has some forage value, but until further research establishes the toxicity of this species to sheep and cattle, prudence suggests managers use caution when allowing animals to graze whitetop-infested rangelands by providing supplemental iodine, utilizing mature and nonlactating animals, and reducing opportunities for animals to consume the plant.
    • Plant structure and the acceptability of different grasses to sheep

      O'Reagain, P. J. (Society for Range Management, 1993-05-01)
      Plant structure should be an important determinant of species acceptability to grazing ungulates functioning under various time-energy constraints. The acceptability of 9 grasses to sheep grazing a secondary grassland community in spring, summer, and autumn in South Africa was related to the following species attributes: plant height, leaf table height, tussock diameter, stemminess, percent leaf, leaf density, percent dry matter (DM), leaf tensile strength, and leaf crude protein (CP). Species acceptability over the grazing season was positively related to tussock diameter (P less than or equal to 0.05) but negatively related (P less than or equal to 0.01) to leaf tensile strength and DM. Discriminant function analysis successfully discriminated between species in different acceptability classes in summer (P less than or equal to 0.05) and autumn (P less than or equal to 0.01) using a combination of plant structure and leaf quality attributes. Correspondence analysis indicated that preferred species were generally short and nonstemmy and had leaves of low DM, low tensile strength, and high crude protein content. Conversely, avoided species tended to be tall and stemmy with a high leaf table height, and had leaves of high DM and tensile strength but low CP levels. It is concluded that, for sheep, acceptability is determined by a combination of plant structure and leaf quality attributes.
    • Technical Notes: Botanical components of annual Mediterranean grassland as determined by point-intercept and clipping methods

      Glatzle, A.; Mechel, A.; Va, M. E. (Society for Range Management, 1993-05-01)
      Three methods for determining proportions of botanical components, i.e., grasses, legumes, and forbs (nonleguminous dicots), of continuously grazed Mediterranean pastures were compared. Percentage contribution to dry matter yield was determined by sample clipping and separating into botanical components. Both percentage of sward and specific contribution were determined by the point-intercept method. These were defined by the relative contribution of 1 botanical component to the total number of counted intercepts between 200 pins inserted vertically into the sward and all botanical components. For specific contribution only the number of pins contacted by the various botanical components were considered, whereas for percentage of sward even multiple contacts between a pin and plant parts of a particular botanical component were taken into account. Percentage contribution was highly significantly correlated with percentage of sward (R = 0.92) and specific contribution (R = 0.93) running the analyses across all botanical components, although there was a significant trend to underestimate forbs and overestimate legumes by the point-intercept methods. It is concluded, however, that for most practical purposes determination of specific contribution, the least laborious method, should give satisfactory estimates of percentage contribution.
    • Viewpoint: Selection for improved drought response in cool-season grasses

      Johnson, D. A.; Asay, K. H. (Society for Range Management, 1993-05-01)
      Water limits the establishment, growth, and production of cool-season grasses on semiarid rangelands, and plant improvement programs for these areas must be capable of screening breeding lines for response to drought. Although many techniques to evaluate various morphological and physiological characteristics have been proposed, few have been used successfully in plant breeding programs. Consequently, a need exists to identify and develop rapid, reliable screening techniques that can assess integrated plant response to drought in large plant populations. Improved seedling emergence has been achieved in Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] by selecting for emergence from a deep seeding depth and long coleoptiles. Water uptake by roots is critical, and screening for enhanced seedling root growth in cool-season grasses offers considerable promise. In spite of the important role that stomatal control has in regulating plant water loss, limited success has been achieved in incorporating desirable stomatal characteristics into improved grass cultivars. Although osmotic adjustment appears beneficial in some crop species, more research is needed before cool-season grasses should be selected based on osmotic adjustment. Selection for improved water-use efficiency in cool-season grasses based on carbon isotope discrimination is a promising approach. Successful incorporation of these various traits into improved cool-season grass cultivars necessitates close cooperation between breeders and physiologists.
    • Water quality effects on stability and phytotoxicity of picloram and clopyralid

      Whisenant, S. G.; Bovey, R. W. (Society for Range Management, 1993-05-01)
      Water quality effects on stability of picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) and clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were evaluated by determining their concentrations in spray mixtures 0, 48, and 168 hours after mixing. Gas chromatography was used to evaluate picloram and clopyralid concentrations in spray solutions mixed with different water sources or buffered water solutions. At 168 hours picloram concentrations in water from La Copita and Midland, Texas, were 11 and 12% lower than at 0-hour and 5 and 6% lower than picloram concentrations in distilled water at 168 hours. Water quality effects on phytotoxicity to honey mesquite (Prosopis glandulosa) were evaluated at 0 and 168 hours after mixing the spray solution. Water quality had no effect on clopyralid phytotoxicity to honey mesquite at either 0 or 168 hours after mixing. Phytotoxicity to honey mesquite was reduced 42% when picloram mixtures were used 168 hours after mixing with water from La Copita. This indicates the potential for reduced phytotoxicity from picloram when prepared spray solutions are not used for 7 days.