• Tannin and in vitro digestibility of tropical browse: predictive equations

      Conklin, N. L. (Society for Range Management, 1994-09-01)
      Summative equations to predict digestibility of tropical browse species for cattle were tested by comparison to in vitro digestibility. Four equations were used for the comparison: first the 2 Van Soest equations, 1 using sulfuric acid lignin and the other using permanganate lignin, neither of which have a correction for tannins. And second, the 2 Horvath equations, each using 1 of the 2 above mentioned lignin values and both include a value for tannin content. The Van Soest equation using permanganate lignin and the Horvath equation using sulfuric acid lignin predicted the in vitro digestibilities of the leaf species quite well (r = 0.89 for both). The same Horvath equation predicted the digestibility of the high tannin species better than the Van Soest equation (r = 0.93 versus 0.84). For initial evaluation and ranking of browse species suitable for future research efforts, either equation suitable.
    • Technical Note: Mechanical despining of plains pricklypear

      Mueller, D. M.; Forwood, J. R. (Society for Range Management, 1994-09-01)
      Plains pricklypear cactus (Opuntia polyacantha L.) is abundant on the Central Great Plains, producing dry matter yields from 1,500 to 2,000 kg/ha. Although pricklypear is high in energy and palatable, long sharp spines make it, and vegetation immediately surrounding it, unavailable to livestock. The possibility of simultaneously controlling and feeding plains pricklypear led to development of machinery for harvesting and despining cactus. The mechanical despiner described here adequately removed spines from pads during periods of low relative humidity. Softening of cactus spines due to high relative humidity resulted in failure of the despiner to adequately remove spines. Cattle readily ate despined cactus in the winter when green forage was unavailable.
    • Toxic alkaloid levels in tall larkspur (Delphinium barbeyi) in western Colorado

      Pfister, J. A.; Manners, G. D.; Gardner, D. R.; Ralphs, M. H. (Society for Range Management, 1994-09-01)
      Consumption of tall larkspur (Delphinium barbeyi L. Huth.) can be fatal to cattle grazing mountain rangeland during summer. Tall larkspur contains many alkaloids, but virtually all the toxicity is caused by methyl succidimido anthranoyl lycoctonine-type (MSAL) diterpenoid alkaloids. We measured the concentration of MSAL alkaloids (% of dry matter) in tall larkspur in various phenological stages during 1990, 1991, and 1992 near Yampa, Colorado. The site represented tall larkspur-infested rangelands on the western slope of the Rocky Mountains. Toxic alkaloid concentrations were greatest (0.4 to 0.6%) early in the growing season (bud stage). Toxic alkaloid concentrations were generally static during the flower and pod stages, or increased during the pod stage. Immature leaves had greater MSAL alkaloid concentrations early in the growing season compared to flowering parts. Alkaloid concentrations in pods were greater than in leaves (P<0.05; pod stage), as pod concentrations increased to 0.4% late in the growing season. In 2 of 3 years, plant parts did not differ in MSAL alkaloid concentrations, although weather conditions differed each year. Concentrations of toxic alkaloids did not seem to influence amounts of tall larkspur consumed by grazing cattle on the same sampling dates. Many livestock producers defer grazing of tall larkspur ranges until the plant is in the pod stage because of a general belief that toxicity is greatly reduced. Our results suggest that grazing tall larkspur ranges during the pod stage may exacerbate cattle losses if MSAL alkaloid concentrations do not decrease, yet consumption by cattle increases.
    • Understanding cause/effect relationships in stocking rate change over time

      Rowan, R. C.; White, L. D.; Conner, J. R. (Society for Range Management, 1994-09-01)
      Decisions made by Texas ranchers over a 10 year period (1980-1990) concerning stocking rate levels were dominated by perceptions about weather. A regression model explained 64% of the variability in stocking rate change over time, with the rainfall/drought variable explaining the majority of variability. As ranchers' perception of a positive rainfall effect increased, so did stocking rates, and vice versa. Although the presence or absence of rainfall cannot be managed per se, proactive stocking decisions should include a strategy for adjusting stocking levels in response to changing environmental conditions. Other factors with significant (alpha = 0.05), albeit trivial, path coefficients on stocking rate change were age, grazing rights (owned vs. leased), traditional stocking rate factors, traditional grazing program factors, and weed/brush information factors. Older ranchers (> 65 years) and ranchers who leased all of their rangeland tended to decrease stocking rates over time. Rangeland operators indicated they considered "improved livestock performance" as the most important benefit from initiating a grazing program. Evidence also suggested that ranchers who rely on their neighbors for advice about weed/brush decisions are not benefitting from the latest technology information. Adoption of economic factors (cost/benefits) for selection of weed/brush technology did not have a significant impact on stocking rates over the 10 year period.
    • Variation of BLM employee attitudes toward environmental conditions on rangelands

      Richards, R. T.; Huntsinger, L. (Society for Range Management, 1994-09-01)
      Using survey data collected as part of a comprehensive reevaluation of the Vale Rangeland Rehabilitation Project in eastern Oregon, this exploratory study examined variation in attitudes of Bureau of Land Management (BLM) employees toward rangeland environmental conditions. Almost one-half of the BLM employees surveyed believed the loss of streamside vegetation (48%) and streambank erosion (42%) were widespread problems on Vale rangelands. Approximately a quarter of the respondents believed rangeland soil loss (24%) and overgrazing (26%) were problems, while only a tenth believed water pollution (10%) was a problem on many or most areas. A composite scale of these attitude toward environmental conditions on rangelands was developed and assessed. The composite scale was regressed on respondents' regional affiliation, length of service, and ideological attitudes towards government role in natural resource management. In contrast to findings from studies for USFS employees, attitudes toward range environmental conditions were not determined by regional affiliation or length of service (P > 0.05). Rather, BLM employee attitudes toward range environmental conditions were found to vary by the interaction of length of service in the agency and attitude toward government's role in regulating water quality (P < 0.05) and managing livestock grazing (P < 0.01). As length of service increases, core beliefs, professional norms, or client constituencies may not polarize employee attitudes but rather moderate them over time. The accumulation of environmental knowledge may also tend to influence environmental attitudes so that ideological attitudes may have a weaker effect as time passes and expertise expands.
    • Water balance in pure stand of Lehmann lovegrass

      Frasier, G. W.; Cox, J. R. (Society for Range Management, 1994-09-01)
      Lehmann lovegrass (Eragrostis lehmanniana Nees), an introduced warm season grass, has invaded grasslands in southern Arizona, in many areas replacing the native warm-season grasses. A water balance evaluation in a pure stand of Lehmann lovegrass showed that more soil water was used through evapotranspiration than occurred as precipitation during 2 years of a 3-year study period. During the winter season, an appreciable amount of water was used by Lehmann lovegrass or lost by evaporation from the soil surface. The remaining available soil water was used in the spring dry period. In the dry early spring the soil water contents (to depths of 120 cm) were less than the traditional wilting point tension of -1.5 MPa. The invasion of Lehmann lovegrass into grasslands of southern Arizona is partially related to its ability to utilize soil water during parts of the year when the native species are dormant and also to extract water from the soil profile to very low water contents.