Toxic Alkaloid Concentrations Research Articles

Mineral-salt supplementation to ameliorate larkspur poisoning in cattle.

Larkspurs (Delphinium spp.) are native forbs that are poisonous to cattle and cost livestock producers millions of dollars in losses each year. Macro and micro minerals are required for normal functioning of essentially all metabolic processes in ruminants. The role that mineral status may play in larkspur poisoning in cattle is not clear. In this study, we seek to determine the effects a mineral-salt supplement, commonly used by cattle producers, to potentially reduce cattle losses to larkspur. The ability of mineral-salt supplementation to alter susceptibility to larkspur toxicosis was evaluated in a pen study. Animals supplemented with mineral-salt were found to be less susceptible to larkspur poisoning than the non-supplemented animals. A separate group of animals were then grazed on larkspur infested rangelands. One group was supplemented with a mineral-salt mix and the other group did not receive any mineral-salt. Supplementing cattle with the mineral-salt mix did not alter larkspur consumption (P > 0.05). However, overall larkspur consumption was low and averaged 3 ± 1.0% and 2 ± 1.1% for cattle supplemented with mineral and non-supplemented, respectively. Serum was collected from animals once a week during the grazing study. Average and maximum serum concentrations of toxic larkspur alkaloids were numerically higher in mineral-salt supplemented cattle compared with the non-supplemented animals. Results from the pen study suggest that a good mineral supplementation program will provide a protective effect for animals grazing in larkspur-infested ranges. The mineral-salt supplemented steers, in the grazing study, were not observed to consume less larkspur than the non-supplemented animals; however, the mineral-salt supplemented animals had higher concentrations of larkspur alkaloids in their serum indicating they may be able to tolerate higher larkspur consumption. The data also indicate that mineral-salt supplementation must be continuous throughout the time the animals are grazing these rangelands as the positive effects can be lost within 30 d post supplementation.

Discovery of the directionally detoxification effect and chemical mechanism of Ginseng-Fuzi co-decoction based on real-time online filtration electrospray ionization mass spectrometry

BackgroundThe synergic action of compound prescriptions is an important feature and core advantage of traditional medicine. Ginseng-Fuzi decoction is a classic compatible phytomedicine in China, of which Ginseng can effectively reduce the toxicity of Fuzi in clinical, but the detoxification chemical mechanism is still unclear. PurposeDevelop a novel method for real-time tracking and monitoring of complex substances in the decoction system of traditional Chinese medicine to uncover the detoxification effect Ginseng on Fuzi and explore the possible chemical reaction mechanism of Ginseng-Fuzi co-decoction. MethodsA novel real-time monitoring system, online filtration electrospray ionization mass spectrometry, was developed for extremely complex substances analysis in the decoction of traditional medicine compounds to uncover the directionally detoxification effect and the mechanism of compatibility interaction. ResultsNine key alkaloids and 7 ginsenosides in Ginseng-Fuzi decoction were simultaneously in-situ monitoring in positive ion mode or negative ion mode respectively. Both types of targeted analytes had satisfactory MS signal response for real-time qualitative and quantitative analysis with high precision (RSD < 14.04%) and low LLODs (0.002 ng/ml-10 ng/ml). Through long-term tracking analysis, the exact detoxification and synergistic effect of Ginseng-Fuzi decoction were confirmed as the concentration of main toxic alkaloids decreased (e.g. the content of mesaconitine has been reduced by about 38%) and the main active monoester alkaloids increased obviously. More importantly, the possible molecular mechanism of the detoxification effect of Ginseng compatibility was revealed for the first time, which was the nucleophilic substitution reaction of diester alkaloids catalyzed by fatty acids. ConclusionThis study revealed the exact effect of co-decoction of Ginseng and Fuzi at the molecular level and the chemical reaction mechanism of fatty acid-catalyzed degradation of toxic diester-type alkaloids. The comprehensive multi-component real-time monitoring strategy for complex traditional medicine compounds developed and implemented here has important demonstration significance for revealing the scientific connotation of the compatibility of compound traditional medicine.

Tissue Accumulations of Toxic Aconitum Alkaloids after Short-Term and Long-Term Oral Administrations of Clinically Used Radix Aconiti Lateralis Preparations in Rats.

Although Radix Aconiti Lateralis (Fuzi) is an extensively used traditional Chinese medicine with promising therapeutic effects and relatively well-reported toxicities, the related toxic aconitum alkaloid concentrations in major organs after its short-term and long-term intake during clinical practice are still not known. To give a comprehensive understanding of Fuzi-induced toxicities, current study is proposed aiming to investigate the biodistribution of the six toxic alkaloids in Fuzi, namely Aconitine (AC), Hypaconitine (HA), Mesaconitine (MA), Benzoylaconine (BAC), Benzoylhypaconine (BHA) and Benzoylmesaconine (BMA), after its oral administrations at clinically relevant dosing regimen. A ultra-performance liquid chromatography-tandem mass spectrometry (UPLC–MS/MS) method was developed and validated for simultaneous quantification of six toxic alkaloids in plasma, urine and major organs of Sprague Dawley rats after oral administrations of two commonly used Fuzi preparations, namely Heishunpian and Paofupian, at their clinically relevant dose for single and 15-days. Among the studied toxic alkaloids and organs, BMA demonstrated the highest concentrations in all studied organs with liver containing the highest amount of the studied alkaloids, indicating their potential hepatotoxicity. Moreover, tissue accumulation of toxic alkaloids after multiple dose was observed, suggesting the needs for dose adjustment and more attention to the toxicities induced by chronic use of Fuzi in patients.

Distasteful Nectar Deters Floral Robbery

Toxic nectar is an ecological paradox [1, 2]. Plants divert substantial resources to produce nectar thatattracts pollinators [3], but toxins in this rewardcould disrupt the mutualism and reduce plant fitness [4]. Alternatively, such compounds could protect nectar from robbers [2], provided that they do not significantly alter pollinator visitation to the detriment of plant fitness [1, 5-8]. Indeed, very few studies have investigated the role of plant toxins in nectar for defense against nectar robbers [4, 9, 10]. Here, we compared two Aconitum species (A.napellus and A.lycoctonum) that have flowers specialized for long-tongued bumblebee pollinators (Bombus hortorum) but are occasionally robbed by short-tongued bumblebees (B.terrestris) [6, 11-13]. Pollinator visits to flowers were much more frequent than by robbers, but visits correlated negatively with nectar alkaloid concentration and declined sharply between 200 and 380 ppm. However, alkaloid concentrations of>20 ppm were deterrent to B.terrestris, suggesting that robbers were less tolerant of nectar alkaloids. Nectar of both plant species contained similar concentrations of carbohydrates and toxic alkaloids, but A.lycoctonum was more likely to secrete nectar in each flower and was also visited more frequently by pollinators and robbers. We conclude that alkaloids in Aconitum spp. nectar affect rates ofboth pollinator visitation and robbery but may have co-evolved with nectar availability to maintain the fitness benefits of specialized plant-pollinator relationships. Chemical defense of nectar is, however, ultimately constrained by pollinator gustatory sensitivity.

Ecophysiological Responses of Tall Fescue Genotypes to Fungal Endophyte Infection, Elevated Temperature, and Precipitation

ABSTRACTTall fescue (Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.) can form a symbiosis with the fungal endophyte Epichloë coenophiala, whose presence often benefits the plant, depending on plant and fungal genetics and the prevailing environmental conditions. Despite this symbiosis having agricultural, economic, and ecological importance, relatively little is known regarding its response to predicted global climate change. We quantified the ecophysiological responses of four tall fescue genetic clone pairs, where each pair consisted of one endophyte‐infected (E+) and one endophyte‐free clone, to climate change factors of annually elevated temperature and seasonally increased precipitation. Endophyte presence increased fescue tillering and biomass production in the elevated temperature treatment and greatly enhanced the ability of two of the fescue clones to recover from the hot and unusually dry summer. Surprisingly, endophyte infection also stimulated biomass production and photosynthesis rates (for one clone) in the most mesic treatment (additional precipitation). Toxic ergot alkaloid concentrations increased in E+ individuals exposed to elevated temperatures, particularly in the fall, but the strength of the response varied across E+ genotypes. Overall, this study suggests that choice of plant and endophyte genetic material will be important in determining the productivity, toxicity, and resilience of tall fescue pastures under future climate conditions.

Warming reduces tall fescue abundance but stimulates toxic alkaloid concentrations in transition zone pastures of the U.S.

Tall fescue pastures cover extensive acreage in the eastern half of the United States and contribute to important ecosystem services, including the provisioning of forage for grazing livestock. Yet little is known concerning how these pastures will respond to climate change. Tall fescue's ability to persist and provide forage under a warmer and wetter environment, as is predicted for much of this region as a result of climate change, will likely depend on a symbiotic relationship the plant can form with the fungal endophyte, Epichloë coenophiala. While this symbiosis can confer environmental stress tolerance to the plant, the endophyte also produces alkaloids toxic to insects (e.g., lolines) and mammals (ergots; which can cause “fescue toxicosis” in grazing animals). The negative animal health and economic consequences of fescue toxicosis make understanding the response of the tall fescue symbiosis to climate change critical for the region. We experimentally increased temperature (+3°C) and growing season precipitation (+30% of the long-term mean) from 2009–2013 in a mixed species pasture, that included a tall fescue population that was 40% endophyte-infected. Warming reduced the relative abundance of tall fescue within the plant community, and additional precipitation did not ameliorate this effect. Warming did not alter the incidence of endophyte infection within the tall fescue population; however, warming significantly increased concentrations of ergot alkaloids (by 30–40%) in fall-harvested endophyte-infected individuals. Warming alone did not affect loline alkaloid concentrations, but when combined with additional precipitation, levels increased in fall-harvested material. Although future warming may reduce the dominance of tall fescue in eastern U.S. pastures and have limited effect on the incidence of endophyte infection, persisting endophyte-infected tall fescue will have higher concentrations of toxic alkaloids which may exacerbate fescue toxicosis.

Independent Recruitment of a Flavin-Dependent Monooxygenase for Safe Accumulation of Sequestered Pyrrolizidine Alkaloids in Grasshoppers and Moths

Several insect lineages have developed diverse strategies to sequester toxic pyrrolizidine alkaloids from food-plants for their own defense. Here, we show that in two highly divergent insect taxa, the hemimetabolous grasshoppers and the holometabolous butterflies, an almost identical strategy evolved independently for safe accumulation of pyrrolizidine alkaloids. This strategy involves a pyrrolizidine alkaloid N-oxygenase that transfers the pyrrolizidine alkaloids to their respective N-oxide, enabling the insects to avoid high concentrations of toxic pyrrolizidine alkaloids in the hemolymph. We have identified a pyrrolizidine alkaloid N-oxygenase, which is a flavin-dependent monooxygenase, of the grasshopper Zonocerus variegatus. After heterologous expression in E. coli, this enzyme shows high specificity for pyrrolizidine alkaloids of various structural types and for the tropane alkaloid atropine as substrates, a property that has been described previously for a pyrrolizidine alkaloid N-oxygenase of the arctiid moth Grammia geneura. Phylogenetic analyses of insect flavin-dependent monooxygenase sequences suggest that independent gene duplication events preceded the establishment of this specific enzyme in the lineages of the grasshoppers and of arctiid moths. Two further flavin-dependent monooxygenase sequences have been identified from Z. variegatus sharing amino acid identities of approximately 78% to the pyrrolizidine alkaloid N-oxygenase. After heterologous expression, both enzymes are also able to catalyze the N-oxygenation of pyrrolizidine alkaloids, albeit with a 400-fold lower specific activity. With respect to the high sequence identity between the three Z. variegatus sequences this ability to N-oxygenize pyrrolizidine alkaloids is interpreted as a relict of a former bifunctional ancestor gene of which one of the gene copies optimized this activity for the specific adaptation to pyrrolizidine alkaloid containing food plants.

Cattle Grazing Toxic Delphinium andersonii in South-Central Idaho

Abstract Anderson larkspur ( Delphinium andersonii A. Gray) is a toxic plant responsible for cattle death losses in the western United States. The objectives of the present study were to determine when cattle consumed Anderson larkspur in relation to plant phenology and toxicity, and to determine if animal age influenced selection of Anderson larkspur. These grazing studies were conducted on semiarid sagebrush rangeland near Picabo, Idaho. Eight 6–7-yr-old mature Angus cows were used in 2008, whereas during 2009, 12 Angus cattle were used, including six yearling heifers and six 4-yr-old cows. The overall density of Anderson larkspur was 2.8 plants · m −2 during 2008, and 4.9 plants · m −2 during 2009. Total toxic alkaloid concentrations in Anderson larkspur plants were near or above 5 mg · g −1 during both studies. During 2008 consumption peaked during the late flower and pod stage of growth. Overall in 2008 cows ate 3% of their bites as larkspur. During 2009 heifers ate about twice as much Anderson larkspur as did mature cows (5.1% of bites vs. 2.9%, respectively). Heifers repeatedly consumed sufficient larkspur that they collapsed; however, no animals were fatally intoxicated. Heifers appeared to become transiently averted to larkspur; however, heifers resumed consumption of D. andersonii after a period of one to several days of low or no consumption. Livestock management to reduce losses to Anderson larkspur should include timed grazing to avoid infested pastures during full flower to pod phenological stages, and grazing with older animals rather than yearling heifers.

Traits for predator selection on Pentaclethra macroloba seeds

Pentaclethra macroloba (Fabaceae: Mimosoidea) is a dominant species of canopy tree in Costa Rica’s Caribbean lowlands, constituting up to 40% of the local tree population in some areas. It has been suggested that P. macroloba’s dominance is due in part to low post-dispersal seed depredation, as few terrestrial seed predators can tolerate the high concentration of toxic alkaloids and free amino acids. Seeds are not immune from depredation, however. Several species of parrots and squirrels have been observed depredating pre-dehiscent legumes and may present selective pressure on P. macroloba recruitment. In this study, we assessed depredation patterns in P. macroloba to (1) determine if predators use legume and seed traits to select food items, (2) determine if such patterns represent an optimal foraging strategy for vertebrate predators, and (3) explore potential consequences of depredation on P. macroloba. Seed depredation was not correlated with legume valve side, legume size, seed number, or seed compartment size, though seeds at the distal end of legumes were more often extracted. Depredation patterns do not indicate that seed predators are foraging optimally and may be quickly satiated due to their low toxicity tolerance the abundance of seeds. Despite a lack of predator selection of various legume and seed characteristics, legume damage caused by depredation may interfere with the explosive dehiscence of P. macroloba and constitute a significant recruitment barrier.

Consumption of Low Larkspur (Delphinium nuttallianum) by Grazing Sheep

Abstract Low larkspur ( Delphinium nuttallianum Pritz.) poisoning causes serious economic loss to livestock producers that graze cattle on foothill and mountain ranges in western North America. In general, all Delphinium spp. are five times less toxic to sheep than to cattle. Because low larkspurs are less toxic to sheep than cattle, grazing sheep before cattle on rangelands with dense populations of low larkspur can reduce larkspur density and risk of poisoning to grazing cattle. All previous published work on sheep and larkspur interactions has involved tall larkspurs. This series of studies was conducted to determine if sheep would consume sufficient low larkspur to reduce subsequent risk to cattle. Four summer trials were conducted in Collbran, Colorado, and Soda Springs, Idaho on pastures with dense (> 9 plants · m −2 ) low larkspur populations. In all trials, sheep ate very little low larkspur ( −1 for 9 d), sheep consumed little low larkspur, but animals appeared to trample much of the low larkspur. Toxic alkaloid concentrations in low larkspur ranged from 1.1 mg · g −1 to 1.6 mg · g −1 in all trials. The use of sheep to graze low larkspurs to reduce subsequent consumption by grazing cattle does not appear to be a viable option.

HPLC‐MS analysis of toxic norditerpenoid alkaloids: refinement of toxicity assessment of low larkspurs (Delphinium spp.)

The low larkspurs (Delphinium nuttallianum and D. andersonii) are two toxic plant species that are often fatally ingested by cattle on western USA rangelands. To assess the potential toxicity of the plants, methods are needed to identify and quantify the toxic N-methylsuccinimidoanthranoyllycacontine type alkaloids in the plant. To compare normal-phase and reverse-phase HPLC-MS methods of analysis for detection and identification of toxic alkaloids in two species of toxic larkspur plants and to define the toxic alkaloids found in Delphinium nuttallianum and D. andersonii collected from several sites in the western USA. The major toxic alkaloids found in the low larkspurs included methyllycaconitine, nudicauline, 14-deacetylnudicauline and geyerline. Other toxic alkaloids detected at lower concentrations included 16-deacetylgeyerline, grandiflorine, bearline, 14-acetylbearline, barbinine, 16-demethylnudicauline and three additional isomers of bearline. Total toxic alkaloid concentrations ranged from 0.72 mg/g (d.w.) to 7.02 mg/g determined by reverse-phase HPLC-MS. The low larkspurs contain a number of toxic alkaloids in addition to the alkaloid methyllycaconitine that need to be assessed when considering the toxicity of the plant. Both normal-phase and reverse-phase HPLC methods are adequate to detect and quantify the alkaloids. The reverse-phase separation may be preferred due to readily available columns, reduced solvent use and simplicity of the electrospray ionisation source.

Toxic Alkaloid Concentrations in Delphinium Nuttallianum, Delphinium Andersonii, and Delphinium Geyeri in the Intermountain Region

Low larkspurs (Delphinium nuttalliunum Pritz., Delphinium andersonii Gray) and plains larkspur (Delphinium geyeri Greene) often poison cattle grazing on western North American rangelands. The dominant toxic alkaloid in larkspur is methyllycaconitine (MLA); other very toxic alkaloids in low and plains larkspurs are nudicauline and geyerline. Toxic alkaloid concentrations in larkspur near or above 3 mg · g−1 present significant risk to grazing cattle. D. nuttallianum from Utah and Colorado, D. andersonii from northern Arizona, and plains larkspur (D. geyeri) from Wyoming were collected for analysis. Concentrations of MLA in D. nuttallianum ranged from 0.8 to 4.5 mg · g−1 in Utah and Colorado; total toxic alkaloid concentrations were often above 3 mg · g−1. D. nuttallianum differed (P = 0.09) in MLA concentration between locations but not phenological stages (P = 0.41). Concentrations of nudicauline ranged from 0.7 to 4 mg · g−1 in D. nuttallianum and were different (P = 0.01) between locations and phenological stages (P = 0.004). D. andersonii was consistently toxic because the total toxic alkaloid concentration fluctuated from 3 to 6 mg · g−1 over the growing season. The concentration of geyerline in D. andersonii was equal to or greater than MLA at each phenological stage, thus adding to the toxicity. The concentration of toxic alkaloids in D. geyeri was typically highest (2–4 mg · g−1) in immature plants, although toxic alkaloid concentrations in plants during the pod stage of growth sometimes increased. Only trace amounts of nudicauline were found in D. geyeri, as most of the alkaloid fraction was other N-(methylsuccinimido) anthranoyllycoctonine (MSAL) alkaloids. Total alkaloid concentration (MSAL and non-MSAL alkaloids) in D. geyeri sometimes exceeded 15 mg · g−1. Concentrations of toxic alkaloids in D. nuttalliunum, D. andersonii, and D. geyeri often did not significantly decline during the growing season as typically found in tall larkspurs. Thus, risk to grazing cattle may remain high until these plants are dormant.

Distribution of norditerpene alkaloids in tall larkspur plant parts through the growing season.

Previous research showed that toxic and total alkaloid pools in tall larkspur (Delphinium barbeyi) increased during early growth, then declined precipitously during the late flower and pod stage of growth. The objective of this study was to measure the concentration and pools of toxic and total alkaloids in tall larkspur plant parts, including roots, and to evaluate the changes in these pools over the growing season as an estimate of diterpenoid alkaloid kinetics in tall larkspur. Twenty entire plants were harvested at each phenological stage: beginning of growth in the spring, early flower, early pod, late pod, and senescence. The plants were separated into their respective parts, freeze-dried, extracted, and analyzed for toxic and total alkaloid concentration, and alkaloid pools were calculated. Concentration of toxic and total alkaloids in leaves and stems declined as the plants matured, while concentration in flowers and pods increased (P < 0.004). Concentration of alkaloids in the root declined in the early growth, then increased at the end of the season (P = 0.002). Alkaloid pools in the root decreased during early growth, with a corresponding increase of pools in foliar parts. In the late flower and pod stage, alkaloid pools in the leaves and stems declined rapidly, while the pool in the crown and roots tended to increase.

Management of three toxic Delphinium species based on alkaloid concentrations

A systematic approach to the taxonomic classification of the tall larkspur complex (Delphinium spp.) has been developed and implemented using molecular genetics, plant morphology, and alkaloid profiles, as shown in other papers in this series. This approach supports the classification of three distinct species ( D. glaucum, D. barbeyi and D. occidentale), as the species differ in genetics and toxicity. Toxic alkaloid concentrations over the growing season were integrated with data on diet selection to make management recommendations on a species-specific basis to reduce the risk of poisoning cattle. Alkaloid concentrations in tall larkspurs in excess of 3 mg/g impart moderate or high risk to grazing cattle if sufficient quantities are consumed. D. glaucum is most toxic, with toxic alkaloid concentrations that exceed 3 mg/g throughout the grazing season until late maturity. Cattle should be denied access to dense patches of this species throughout the grazing season until after seed shatter. Concentration of toxic alkaloids in D. barbeyi is highest in vegetative plants, but D. barbeyi is unpalatable to cattle until flowering racemes begin to elongate. We recommend grazing D. barbeyi ranges early in the season when it is not palatable, then removing cattle from early flowering stage through mid-pod stage when cattle are most likely to be poisoned. Cattle can again safely graze D. barbeyi late in the season when the toxic alkaloid concentration typically declines below 3 mg/g. Some populations of D. occidentale and the D. barbeyi× D. occidentale hybrids do not contain toxic alkaloids, and pose little risk of poisoning throughout the year. Toxicity of northern populations of D. occidentale varies from year-to-year for unknown reasons. Cattle

Predicting toxicity of tall larkspur (Delphinium barbeyi): measurement of the variation in alkaloid concentration among plants and among years.

Tall larkspur (Delphinium barbeyi) is the principal mountain larkspur responsible for the majority of cattle deaths on mountain rangelands in western Colorado and central and southern Utah in the United States. Ten plants in each of two tall larkspur populations in the mountains near Ferron and Salina, Utah, were marked, and single stalks were harvested periodically through the growing season for 4 yr. Toxic alkaloid concentration [alkaloids containing the N-(methylsuccimimido)-anthranilik ester group] was determined by Fourier transform infrared (FTIR) spectroscopy. Individual larkspur plants varied in alkaloid concentrations, especially in early growth (14-38 mg/g). As the concentration declined over the growing season, variation among plants also declined. There were yearly differences in alkaloid concentration among individual plants (P < 0.01) and populations (P < 0.001), even after accounting for differences in phenological growth between years. Variables such as precipitation, temperature, days since snow melt, growing degree days (sum of mean temperature each day from snow melt), and plant height and weight were all considered in a Mallows Cp multiple regression selection procedure to predict alkaloid concentration. The mixed model procedure in SAS adjusted the regression equation for locations and years. Growing degree days was the best single predictor of alkaloid levels: In y = (3.581 - 0.00423 GDD), R2 = 0.85. Internal validation of this equation within individual years and locations from which the equation was developed, produced correlations between observed versus predicted values ranging from r = 0.73 to 0.93. External validations on nine other larkspur populations produced correlations ranging from r = 0.76 to 0.99. This predictive equation can provide a tool for ranchers and land managers to make management decisions of when to graze cattle in larkspur areas.

Clipping and precipitation influences on locoweed vigor, mortality, and toxicity

White locoweed (Oxytropis sericea Nutt. in TG) is widespread throughout the short-grass prairies and mountain grasslands and causes chronic poisoning of cattle, sheep, and horses. The objective of this study was to determine the effect of clipping (simulated grazing) on vigor, mortality and toxic alkaloid concentration of white locoweed. One hundred locoweed plants were marked at each of 3 locations (New Mexico, Colorado, and Utah). Plants were stratified into 2 age/size classes: young/small &lt; 5 stalks; older/large &gt; 7 stalks (n = 50 in each class). Pairs of plants within each age class that were as similar as possible were selected, and 1 of each pair (n = 25) was clipped at ground level annually for 4 years. Vigor indices included number of stalks, number of flowering heads, leaf length, and flowering head height. Mortality was recorded and the toxic alkaloid swainsonine was measured. Clipping did not consistently reduce vigor. Flowering heads/plant declined in most clipped plants (P &lt; 0.05), but stalks/plant declined only in large clipped plants in Utah and small clipped plants in New Mexico (P &lt; 0.01), and clipping did not greatly affect leaf length or flowering head height. Clipping did not increase mortality, and did not affect swainsonine concentration. However, there was a natural die-off that may have been related to precipitation. There were negative correlations between precipitation and locoweed mortality (r = -0.42 to -0.84), with most of the marked plants dying during the recent drought. Grazing locoweed for short periods would likely not affect its vigor or toxicity, but its population dynamics were affected by drought.

Influence of defoliation on toxic alkaloid concentration and alkaloid pools in tall larkspur.

This study was replicated at two locations in the mountains of central Utah. In 1997, ten uniform plants of tall larkspur (Delphinium barbeyi) in the early bud stage (40 cm in height) were selected at each site and clipped at 5 cm above soil level. In 1998, one stalk from each plant was harvested on a weekly basis; in 1999, one stalk was harvested at four times during its phenological development. Toxic and total alkaloid concentrations were measured and alkaloid pools in the entire stalk were calculated. Clipping reduced stalk height to less than 50 cm in 1998 and 65 cm in 1999, compared to over 100 cm in unclipped control plants. Alkaloid concentration was similar to control plants, but toxic alkaloid pools were 70% lower than control plants, because of the reduction in biomass of the stalks. Clipping reduced subsequent vigor and the amount of toxic and total alkaloids in tall larkspur.

Alkaloid levels in Duncecap (Delphinium occidentale) and Tall larkspur (D. barbeyi) grown in reciprocal gardens: separating genetic from environmental influences.

The objective of this study was to determine whether differences in toxicity between Tall larkspur (Delphinium barbeyi) and Duncecap larkspur (D. occidentale) were genetically inherent within the species, or due to environmental influences unique to the different regions where they grow. There was no difference in the concentration of the toxic alkaloids between the two species when grown in common gardens. However, both species had higher concentration of toxic alkaloids when grown in the southern Rocky Mountain region which is characterized by summer monsoonal thunderstorms, compared to summer drought in the north. In a unique occurrence where Duncecap larkspur grew beside Tall larkspur, toxic alkaloids were very low in Duncecap larkspur, but total alkaloid concentration was often higher than in Tall larkspur.

Late Season Toxic Alkaloid Concentrations in Tall Larkspur (Delphinium spp.)

Tall larkspurs [Delphinium barbeyi (L. Huth), D. occidentale (Wats.), D. glaucescens (Rydb.), D. glaucum (Wats.)] pose a serious poisoning threat to cattle on many summer ranges. Livestock producers often defer grazing until larkspur is mature, but spe cific information is lacking on toxic alkaloid concentrations in larkspur from pod stage to senescence. Tall larkspur leaves and seed pods were collected about every 2 weeks during the pod stage to senescence from marked plants in locations in Utah (Logan and Salina), Idaho (Ashton, Humphrey, and Oakley), Colorado (Yampa and Montrose), and California (Carson Pass) from 1995 to 1997. Toxic alkaloid concentions in pods (x ‐ = 2.9 mg/g) exceeded leaf alkaloid concentrations (x = 1.5 mg/g in all species, but the magnitude of the difference varied among the 4 species. Leaves showed a more rapid decrease in toxic alkaloid concentration with plant maturity compared to pods. Seed pods did not begin to lose substantial amounts of toxic alkaloid until larkspur matured and pods began to dessicate. At seed shatter, D. glaucescens pods retained more toxic alkaloid than the other species, and alkaloid concentration was sufficiently high after pods had shattered (3.5 mg/g) to pose a moderate grazing risk. After seed shatter, the toxic alkaloid concentrations in leaves and pods of D. barbeyi, D. occidentale , and D. glaucum were generally less than 2 mg/g; thus, risk of losing cattle would be low for the remainder of the grazing season.

Late season toxic alkaloid concentrations in tall larkspur (Delphinium spp.)

Tall larkspurs [Delphinium barbeyi (L. Huth), D. occidentale (Wats.), D. glaucescens (Rydb.), D. glaucum (Wats.)] pose a serious poisoning threat to cattle on many summer ranges. Livestock producers often defer grazing until larkspur is mature, but specific information is lacking on toxic alkaloid concentrations in larkspur from pod stage to senescence. Tall larkspur leaves and seed pods were collected about every 2 weeks during the pod stage to senescence from marked plants in locations in Utah (Logan and Salina), Idaho (Ashton, Humphrey, and Oakley), Colorado (Yampa and Montrose), and California (Carson Pass) from 1995 to 1997. Toxic alkaloid concentions in pods (average= 2.9mg/g) exceeded leaf alkaloid concentrations (average= 1.5 mg/g in all species, but the magnitude of the difference varied among the 4 species. Leaves showed a more rapid decrease in toxic alkaloid concentration with plant maturity compared to pods. Seed pods did not begin to lose substantial amounts of toxic alkaloid until larkspur matured and pods began to dessicate. At seed shatter, D. glaucescens pods retained more toxic alkaloid than the other species, and alkaloid concentration was sufficiently high after pods had shattered (3.5 mg/g) to pose a moderate grazing risk. After seed shatter, the toxic alkaloid concentrations in leaves and pods of D. barbeyi, D. occidentale, and D. glaucum were generallyless than 2 mg/g; thus, risk of losing cattle would be low for the remainder of the grazing season