Michael H. Ralphs

Locoweed Poisoning in Livestock

354 known species oi Astragalus and 22 species of Oxytropis. Most of these species are nontoxic and are important forages; however, several species are toxic to both livestock and wildlife. Historically toxic species are divided into three groups based on the toxic syndromes observed in livestock: 1) selenium poisoning, 2) nitrotoxin poisoning, and 3) locoism caused by the toxin swainsonine. Plant species associated with each toxic syndrome are listed in Table 1. In North America approximately 25 selenium accumulating species occur in the taxonomic family Astragalus (Table 1). These plants grow in soils with high concentra tions of selenium and are often used as indicators of

Swainsoninine Concentrations and Endophyte Amounts of Undifilum oxytropis in Different Plant Parts of Oxytropis sericea

Locoweeds are Astragalus and Oxytropis species that contain the toxic alkaloid swainsonine. Swainsonine accumulates in all parts of the plant with the highest concentrations found in the above ground parts. A fungal endophyte, Undifilum oxytropis, found in locoweed plant species, is responsible for the synthesis of swainsonine. By using quantitative PCR, the endophyte can be quantified in locoweed species. Endophyte amounts differ between plant parts and in some instances do not mirror the concentrations of swainsonine in the corresponding parts. Two groups of Oxytropis sericea were identified: one that accumulated high concentrations of swainsonine and another where swainsonine was not detected, or concentrations were near the detection threshold. The plants with high swainsonine concentrations had quantitatively higher amounts of endophyte. Alternatively, plants with low or no swainsonine detected had quantitatively lower endophyte amounts. In addition, swainsonine and endophyte concentrations were not distributed uniformly within the same plant when separated into stalks (leaves, scape(s), and flowers/pods). These findings provide evidence as to why plants in the same population accumulate different concentrations of swainsonine, and they have important implications for sampling of locoweed plants.

Influence of Phenological Stage on Swainsonine and Endophyte Concentrations in Oxytropis sericea

Locoweeds are defined as Astragalus and Oxytropis species that cause intoxication due to the alkaloid swainsonine. Swainsonine concentrations in Oxytropis sericea were influenced by location, plant part, and the developmental stage of the plant. Concentrations followed similar trends at each location, generally increasing over the growing season in above-ground parts until the plant reaches maturity with no change in concentration in the crowns. At the onset of senescence, swainsonine decreased in floral parts to less than half of the peak concentration. Similar to swainsonine concentrations, endophyte amounts were influenced by location, plant part, and the developmental stage of the plant. Likewise, endophyte amounts generally increased over the growing season in above ground parts and remained static in the crowns at all four locations. Swainsonine in Oxytropis sericea was positively associated with the endophyte Undifilum, which is responsible for swainsonine biosynthesis.

Alkaloid Profiles, Concentration, and Pools in Velvet Lupine (Lupinus leucophyllus) Over the Growing Season

Lupinus leucophyllus is one of many lupine species known to contain toxic and/or teratogenic alkaloids that can cause congenital birth defects. The concentrations of total alkaloids and the individual major alkaloids were measured in three different years from different plant parts over the phenological development of the plant. All of the alkaloids were found in the different plant tissues throughout the growing season, although their levels varied in different tissues. Concentrations of total alkaloids and the individual alkaloids varied on an annual basis and in their distribution in the different tissues. Anagyrine levels were highest in the floral tissue, lupanine and unknown F accumulated to the greatest level in the vegetative tissue, and 5,6-dehydrolupanine accumulated to the highest level in the stem. These alkaloids appear to be in a metabolically active state with the teratogenic alkaloid anagyrine accumulating to its highest level in the developing seed. The latter is, thus, the phenological stage posing the greatest danger to grazing livestock.

WHITE LOCOWEED TOXICITY IS FACILITATED BY A FUNGAL ENDOPHYTE AND NITROGEN-FIXING BACTERIA

Mutualistic interactions with fungal endophytes and dinitrogen-fixing bacteria are known to exert key biological influences on the host plant. The influence of a fungal endophyte alkaloid on the toxicity of a plant has been documented in Oxytropis sericea. Oxytropis sericea is a perennial legume responsible for livestock poisoning in western North America. Livestock poisoning is attributed to the alkaloid swainsonine, which is synthesized inside the plant by the fungal endophyte Embellisia sp. In this study, the ability of Oxytropis sericea to form a dinitrogen-fixing symbiosis with Rhizobium and the effects of this symbiosis on the production of swainsonine by Embellisia sp. were evaluated in a greenhouse environment. Seeds of O. sericea were grown in plastic containers. Twenty-week-old O. sericea seedlings were inoculated with four strains of Rhizobium. Twenty weeks after inoculation, plant growth and root nodulation by Rhizobium were measured. Dinitrogen fixation was confirmed using an acetylene reduction assay (ARA) on excised root nodules. Dry leaves were analyzed for swainsonine content. A second set of plants was treated with fungicide to evaluate the effect of reduced fungal endophyte infection on plant growth and swainsonine production. All inoculated plants produced indeterminate nodules. The ARA indicated that 98% of the excised nodules were fixing dinitrogen. Rhizobium-treated plants had greater swainsonine concentrations than the non-inoculated controls. Plants that established from seeds treated with fungicide had lower biomass than non-fungicide-treated controls and plants treated with foliar fungicide. Plants treated with foliar fungicide and the controls had greater swainsonine concentrations than the plants that received seed fungicide. This greenhouse study is the first report of nodulation and dinitrogen fixation in O. sericea. It also demonstrates that dinitrogen fixation increases the production of swainsonine in O. sericea plants infected with Embellisia sp. Results from this study suggest that dinitrogen fixation affects swainsonine production and has the potential to support the symbiosis between Embellisia sp. and O. sericea when soil nitrogen is limited. Oxytropis sericea competitiveness appears to be facilitated by an ability to simultaneously associate with Rhizobium and a fungal symbiont.

Lupine-Induced Crooked Calf Disease: The Last 20 Years

Summary Many of the incidences report only calves that are destroyed. In our experience, there are substantial numbers of affected calves with minor to moderate leg deformities that eventu-ally recover, and perform adequately in the feedlot with minor growth retardation. The real economic losses are not only calf deaths. Costs due to dystocia, caesarian sections, cow deaths, and added veterinary care are also signifi cant. In many cases, lupine-infested pastures are abandoned or grazing is restricted so that potential forage is lost, and other forage must be purchased, thus adding to the eco-nomic toll. The emotional strain on humans from crooked calf losses and expenses is also substantial but diffi cult to quantify for both individual ranch families and their associ-ated communities. Many ranchers that contributed to this report related the emotional stress they felt in anticipating the birth of more deformed calves. Acknowledgments We appreciate the assistance of numerous anonymous ranchers who contributed to this report. We thank Terrie Wierenga, Kermit Price, Andrea Dolbear, and Clint Stonecipher for technical assistance. We appreciate M. E. Barkworth, Director, and K. M. Piep, Assistant Curator, of the Intermountain Herbarium at Utah State University, Logan, Utah, for taxonomic confi rmation of plant specimens.

Cattle Grazing as a Biological Control for Broom Snakeweed: Vegetation Response

Abstract Broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) increases and dominates rangelands following disturbances, such as overgrazing, fire, and drought. However, if cattle can be forced to graze broom snakeweed, they may be used as a biological tool to control it. Cattle grazed broom snakeweed in May and August 2004–2007. Narrow grazing lanes were fenced to restrict availability of herbaceous forage to force cattle to graze broom snakeweed. They used 50–85% of broom snakeweed biomass. Mature broom snakeweed plant density declined because of prolonged drought, but the decline was greater in grazed lanes. At the end of the study, density of mature plants in grazed lanes was 0.31 plants · m−2, compared with 0.79 plants · m−2 in ungrazed pastures. Spring precipitation in 2005 was 65% above average, and a new crop of seedlings established following the spring grazing trial. Seedling establishment was greater in the spring-grazed lanes in which the soil had been recently disturbed, compared with the ungrazed transects and summer-grazed lanes. The cattle were not able to use the large volume of new broom snakeweed plants in the spring-grazed pasture. They did reduce the number of seedlings and juvenile plants in the summer-grazed pasture. Intense grazing pressure and heavy use did not adversely affect crested wheatgrass (Agropyron cristatum [L.] Gaertn.) cover, and it was actually higher in the summer grazed lanes than the ungrazed control transects. In moderate stands of broom snakeweed, cattle can be forced to graze broom snakeweed and reduce its density without adversely affecting the associated crested wheatgrass stand.

The characterization and absolute stereochemistry of barbaline, a diterpenoid alkaloid from Delphinium barbeyi

The structure and absolute stereochemistry of a new diterpenoid alkaloid, barbaline, was determined by NMR spectroscopy techniques and single-crystal X-ray diffraction analysis.

Broom Snakeweed (Gutierrezia sarothrae): Toxicology, Ecology, Control, and Management

Abstract Broom snakeweed is a native weed widely distributed on rangelands of western North America. It often increases to near monocultures following disturbance from overgrazing, fire, or drought. This paper presents an up-to-date review of broom snakeweed toxicology, seed ecology, population cycles, succession, and management. The greatest ecological concern is that broom snakeweed displaces desirable forage for livestock or wildlife and greatly reduces biodiversity. It also is toxic and can cause abortions in all species of livestock. Propagation usually is pulse-driven in wet years, allowing large expanses of even-aged stands to establish and dominate plant communities. Snakeweed can be controlled by prescribed burning or spraying with herbicides. A weed-resistant plant community dominated by competitive grasses can prevent or minimize its reinvasion. Nomenclature: Broom snakeweed, Gutierrezia sarothrae (Pursh) Britton & Rusby GUESA Interpretive Summary: Broom snakeweed is an invasive native subshrub that is distributed widely across rangelands of western North America. In addition to its invasive nature, it contains toxins that can cause death and abortions in livestock. It establishes in years of above-average precipitation following disturbance by fire, drought, or overgrazing. This allows widespread, even-aged stands to develop that can dominate plant communities. Although its populations cycle with climatic patterns, it can be a major factor impeding succession of plant communities. Snakeweed can be controlled with prescribed burning and herbicides; however, a weed-resistant plant community should be established and/or maintained to prevent its reinvasion. Proper grazing management to maintain competitive grasses is essential for suppression of this invasive weed.

Selected Common Poisonous Plants of the United States' Rangelands

Selected Common Poisonous Plants of the United States’ Rangelands DOI:10.2458/azu_rangelands_v31i1_davis