The effect of alkaloid composition of larkspur (Delphinium) species on the intoxication of Angus heifers1.

Cattle losses from larkspur (Delphinium spp.) toxicity are a long-term challenge on the rangelands of western North America. In addition to animal factors that affect livestock poisonings, plant alkaloid composition (chemotype) affects the intoxication of cattle because some chemotypes are significantly more toxic. Differences in larkspur chemotype toxicity are due to the ratios of N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids to non-MSAL-type alkaloids and the concentrations of those alkaloids in the plant material. The objective of this study was to compare the responses of 6 Angus heifers to 6 chemotypes of larkspur using a Latin square study design. These Angus heifers from the USDA-ARS, Meat Animal Research Center in Clay Center, NE, were chosen for this research because they are the most larkspur-susceptible cattle observed to date. The 6 heifers were given an oral dose of dried ground larkspur and tested for muscle weakness with an exercise test (i.e., walk time). The 6 chemotypes of larkspur had non-MSAL to MSAL-type alkaloid ratios ranging from 1.4:1 to 6:1 and were administered at an oral dose of 7.5 mg/kg MSAL-type alkaloids BW. There was a treatment effect due to larkspur chemotype (P < 0.0001), and period effects were not significant (P = 0.6). There were also significant correlations between the length of time walking on a dirt track at 5 to 6 km/h, and total alkaloid dose (r = -0.92, P = 0.0045) and alkaloid ratio (r = -0.81, P = 0.0258). Serum alkaloid concentrations at 24 h after dosing were representative of the relative abundance of the alkaloid in the plant material. Results from this work suggest that total alkaloid concentrations in combination with alkaloid ratios can be used together to accurately predict the plant risk component of larkspur poisoning to grazing cattle. Animal factors such as cattle age, breed, and sex must also be considered to comprehensively manage larkspur risk.

An agent-based model of cattle grazing toxic Geyer's larkspur.

By killing cattle and otherwise complicating management, the many species of larkspur (Delphinium spp.) present a serious, intractable, and complex challenge to livestock grazing management in the western United States. Among the many obstacles to improving our understanding of cattle-larkspur dynamics has been the difficulty of testing different grazing management strategies in the field, as the risk of dead animals is too great. Agent-based models (ABMs) provide an effective method of testing alternate management strategies without risk to livestock. ABMs are especially useful for modeling complex systems such as livestock grazing management, and allow for realistic bottom-up encoding of cattle behavior. Here, we introduce a spatially-explicit, behavior-based ABM of cattle grazing in a pasture with a dangerous amount of Geyer's larkspur (D. geyeri). This model tests the role of herd cohesion and stocking density in larkspur intake, finds that both are key drivers of larkspur-induced toxicosis, and indicates that alteration of these factors within realistic bounds can mitigate risk. Crucially, the model points to herd cohesion, which has received little attention in the discipline, as playing an important role in lethal acute toxicosis. As the first ABM to model grazing behavior at realistic scales, this study also demonstrates the tremendous potential of ABMs to illuminate grazing management dynamics, including fundamental aspects of livestock behavior amidst ecological heterogeneity.

Administering multiple doses of a non N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-containing tall larkspur (Delphinium occidentale) to cattle.

Larkspurs (Delphinium spp.) are a serious toxic plant problem for cattle in western North America. There are two chemotypes of D. occidentale, a more toxic and a less toxic chemotype. The objective of this study was to evaluate the acute toxicity of the less toxic chemotype when administered in multiple doses to cattle. These results suggest that cattle could consume enough of the less toxic chemotype to be poisoned in a range setting.

The Effect of Co-Administration of Death Camas (Zigadenus spp.) and Low Larkspur (Delphinium spp.) in Cattle.

In many rangeland settings, there is more than one potential poisonous plant. Two poisonous plants that are often found growing simultaneously in the same location in North American rangelands are death camas (Zigadenus spp.) and low larkspur (Delphinium spp.). The objective of this study was to determine if co-administration of death camas would exacerbate the toxicity of low larkspur in cattle. Cattle dosed with 2.0 g of death camas/kg BW showed slight frothing and lethargy, whereas cattle dosed with both death camas and low larkspur showed increased clinical signs of poisoning. Although qualitative differences in clinical signs of intoxication in cattle co-treated with death camas and low larkspur were observed, there were not any significant quantitative differences in heart rate or exercise-induced muscle fatigue. Co-treatment with death camas and low larkspur did not affect the serum zygacine kinetics, however, there was a difference in the larkspur alkaloid kinetics in the co-exposure group. Overall, the results from this study suggest that co-exposure to death camas and low larkspur is not significantly more toxic to cattle than exposure to the plants individually. The results from this study increase our knowledge and understanding regarding the acute toxicity of death camas and low larkspur in cattle.

The effect of administering multiple doses of tall larkspur (Delphinium barbeyi) to cattle.

Larkspurs ( spp.) are one of the most serious toxic plant problems on foothill and mountain rangelands in the western United States. A considerable amount of research has been conducted over the years in both field and pen settings. The results of these research efforts have significantly increased our understanding of the poisoning of cattle by larkspurs. However, most of the pen studies conducted thus far have used a dosing regimen of a single bolus dose, which does not accurately mimic the manner by which cattle are poisoned by larkspur while grazing. Consequently, the objective of this study was to evaluate the acute toxicity of tall larkspur ( collected near Manti, UT) when administered in multiple doses, with the intent to identify a no observable adverse effect level (NOAEL). The adverse effect selected for this study was muscle weakness to the point the cattle could no longer remain ambulatory as would be required in a grazing environment, thus becoming sternally recumbent when exercised. Hereford steers were administered various doses of tall larkspur at 12-h intervals for 4 d or until they showed marked signs of muscle weakness. The results suggest that a dose of 2 mg kg∙d -(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids is the NOAEL for a tall larkspur population with a norditerpenoid alkaloid profile containing 4 mg MSAL-type alkaloids/g plant material and 12 mg non-MSAL-type alkaloids/g plant material. Additionally, a computer model was generated to simulate multiple-dosing regimens at the various doses as well as different dosing regimens. The results from this study suggest that a 500-kg steer can consume a daily dose of 1.25 kg of fresh tall larkspur (with a similar alkaloid profile) without becoming severely poisoned (suffering from muscle weakness to the point of recumbency). Additionally, these results indicate that a serum concentration of approximately 355 ng methyllycaconitine/mL may represent a toxic threshold.

The relative toxicity of Delphinium stachydeum in mice and cattle.

Larkspurs (Delphinium spp.) are poisonous plants on rangelands throughout the Western United States and Canada. Larkspur-induced poisoning in cattle is due to norditerpene alkaloids that are represented by two main structural groups of norditerpene alkaloids, the N-(methylsuccinimido) anthranoyllycoctonine type (MSAL-type) and the non-MSAL type. Information on the alkaloid composition and resulting toxicity in mice and cattle is lacking for a number of Delphinium species, including Delphinium stachydeum. The objective of this study was to determine the alkaloid composition of D. stachydeum and to characterize its relative toxicity in mice and cattle compared to two reference species Delphinium barbeyi and Delphinium occidentale. D. stachydeum contains the non-MSAL-type alkaloids but not the MSAL-type alkaloids. D. stachydeum was less toxic than D. barbeyi and D. occidentale in the mouse model. D. stachydeum was less toxic than the MSAL-containing D. barbeyi but much more toxic than the non-MSAL-containing D. occidentale in cattle as measured by heart rate and time of exercise. These results indicate that predictions of Delphinium toxicity can't be accurately made based solely on results from the mouse model or the absence of the MSAL-type alkaloids in the plant.

The effect of low larkspur (Delphinium spp.) co-administration on the acute toxicity of death camas (Zigadenus spp.) in sheep.

In most cases where livestock are poisoned by plants in a range setting, there is more than one potential poisonous plant in the same area. Two poisonous plants that are often found growing simultaneously in the same location are death camas (Zigadenus spp.) and low larkspur (Delphinium spp.). Sheep are known to be susceptible to death camas poisoning while they are thought to be resistant to larkspur. The objective of this study was to determine if co-administration of low larkspur would exacerbate the toxicity of death camas in sheep. A dose finding study was performed to find a dose of death camas that caused minimal clinical signs of poisoning. Sheep were observed for clinical signs of poisoning as well as changes in heart rate and muscle fatigue. Sheep dosed with 1.14 g of death camas per kg BW showed slight frothing and lethargy, whereas sheep dosed with death camas and low larkspur showed slightly more noticeable clinical signs of poisoning. Sheep dosed with only low larkspur, at 7.8 g/kg BW, showed no signs of poisoning. Although we observed a qualitative difference in clinical signs of intoxication in sheep co-treated with death camas and low larkspur we did not detect any quantitative differences in heart rate, exercise-induced muscle fatigue, or differences in serum zygacine kinetics. Consequently, the results from this study suggest that low larkspur does not affect the toxicity of death camas in sheep. The results from this study increase knowledge and understanding regarding the acute toxicity of death camas and low larkspur in sheep. As combined intoxications are most likely common, this information will be useful in further developing management recommendations for ranchers and in designing additional experiments to study the toxicity of death camas to other livestock species.

A toxicokinetic comparison of two species of low larkspur (Delphinium spp.) in cattle.

Low larkspurs have different toxic potentials to livestock due to variation in the individual alkaloids present in the plants. Two species, Delphinium nuttallianum and Delphinium andersonii were dosed to 10 Holstein steers at 10mg and 12 mg toxic alkaloids/kg, respectively. Blood samples were collected periodically for 96 h, analyzed for serum alkaloid concentrations and toxicokinetic parameters calculated for 16-deacetylgeyerline, 14-deacetylnudicauline, methyllycaconitine and geyerline/nudicauline which co-eluted in the serum analysis. The maximum serum alkaloid concentrations and area under the curve values for 16-deacetylgeyerline and geyerline/nudicauline were significantly different between the two groups due to the concentrations of the alkaloids in each larkspur species. The alkaloid elimination half-lives were similar for the two larkspur species. These results suggest the elimination rates of norditerpene alkaloids from different larkspur species in cattle are similar regardless of plant alkaloid composition. The determining factor for larkspur toxicity is the individual alkaloid composition of the plant.

Toxicokinetics of norditerpenoid alkaloids from low larkspur (Delphinium andersonii) orally administered to cattle.

OBJECTIVE: To determine the toxicokinetics of N-(methylsuccinimido)anthranoyllycoctonine-type low larkspur alkaloids in beef cattle. ANIMALS: 5 Black Angus steers and 35 Swiss Webster mice. PROCEDURES: -Low larkspur (Delphinium andersonii) was collected, dried, ground, and administered to 5 steers via oral gavage to provide a dose of 12 mg of N-(methylsuccinimido)-anthranoyllycoctonine alkaloids/kg. Steers were housed in metabolism crates for 96 hours following larkspur administration; heart rate was monitored continuously, and blood samples were collected periodically for analysis of serum concentrations of 16-deacetylgeyerline, methyllycaconitine, geyerline, and nudicauline and assessment of kinetic parameters. The LD(50) of a total alkaloid extract from D andersonii was determined in Swiss Webster mice. RESULTS: -The alkaloids were quickly absorbed, with a maximum serum concentration achieved within 18 hours after administration. Geyerline and nudicauline coeluted as 1 peak and were considered together for toxicokinetic analysis. Mean ± SD elimination half-life was 18.4 ± 4.4 hours, 15.6 ± 1.5 hours, and 16.5 ± 5.1 hours for 16-deacetylgeyerline, methyllycaconitine, and geyerline and nudicauline, respectively. There were significant differences in maximum serum concentration, amount absorbed, and distribution half-life among the 4 alkaloids. The mouse LD(50) was 9.8 mg/kg. CONCLUSIONS AND CLINICAL RELEVANCE: -Results suggested that clinical poisoning was likely to be most severe approximately 18 hours after exposure. Cattle should be closely monitored for at least 36 hours after initial exposure. Additionally, a withdrawal time of approximately 7 days would be required to clear > 99% of the toxic alkaloids from the serum of cattle that have ingested low larkspur.

Comparison of the toxic effects of two duncecap larkspur (Delphinium occidentale) chemotypes in mice and cattle.

OBJECTIVE: To compare the toxic effects of a Delphinium occidentale chemotype containing N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids and a D occidentale chemotype lacking MSAL-type alkaloids in mice and cattle. ANIMALS: 225 male Swiss Webster mice and 11 Black Angus steers. PROCEDURES: 4 collections of larkspur containing MSAL-type alkaloids and 4 collections of larkspur lacking MSAL-type alkaloids were used. From each collection, total alkaloid extracts (0.05 to 0.20 mL) were administered via tail-vein injection in 27 to 29 mice. Dried, finely ground plant material from 1 collection with and 1 collection without MSAL-type alkaloids (doses equivalent to 37.6 mg of total alkaloids/kg) were each administered to 8 cattle via oral gavage in a crossover experiment; 3 cattle received a single dose equivalent to 150.4 mg of total alkaloids/kg (no MSAL-type alkaloids). In mice, clinical effects were monitored; in cattle, heart rate was monitored before (baseline) and 24 hours after treatment. At the 24-hour time point, cattle were exercised as a measure of muscle weakness. RESULTS: In mice, mean LD(50) associated with alkaloid extracts prepared from plants that did or did not contain MSAL-type alkaloids was 2.3 and 54.2 mg/kg, respectively. In cattle at 24 hours after treatment, plant material containing MSAL-type alkaloids significantly increased heart rate from baseline and was associated with exercise-induced collapse; plant material lacking MSAL-type alkaloids had no similar effects. CONCLUSIONS AND CLINICAL RELEVANCE: Taxonomic classification of D occidentale alone was not a good indicator of the toxic risk to grazing cattle.

A toxicokinetic comparison of norditerpenoid alkaloids from Delphinium barbeyi and D. glaucescens in cattle.

Cattle are poisoned by N-(methylsuccinimido) anthranoyllycoctonine type (MSAL-type) and 7,8-methylenedioxylycoctonine type (MDL-type) norditerpenoid alkaloids in Delphinium spp. Alkaloids in D. glaucescens are primarily of the MSAL-type, while D. barbeyi is a mixture of MSAL and MDL-types. The objectives of this study were to determine and compare the toxicokinetics of selected alkaloids from D. glaucescens and D. barbeyi in cattle. The two species of larkspur were dosed to three groups of Angus steers via oral gavage at doses of 8 mg kg⁻¹ MSAL-type alkaloids for D. barbeyi and either 8.0 or 17.0 mg kg⁻¹ MSAL-type alkaloids for D. glaucescens. In cattle dosed with D. barbeyi, serum deltaline (MDL-type) concentrations peaked at 488 ± 272 ng ml⁻¹ at 3 h and serum methyllycaconitine (MSAL-type) concentrations peaked at 831 ± 369 ng ml⁻¹ at 6 h. Deltaline was not detected in the serum of cattle dosed with D. glaucescens. Serum methyllycaconitine concentrations peaked at 497 ± 164 ng ml⁻¹ at 18 h, and 1089 ± 649 ng ml⁻¹ at 24 h for the 8 mg kg⁻¹ and 17 mg kg⁻¹ doses of D. glaucescens respectively. There were significant differences between the maximum serum concentrations and the area under the curve for the two doses of D. glaucescens but not D. barbeyi. Results from this experiment support the recommendation that approximately 7 days are required to clear 99% of the toxic alkaloids from the serum of animals orally dosed with D. barbeyi or D. glaucescens, and that MDL-type alkaloids play an important role in the toxicity of Delphinium spp. in cattle.

Influence of 7,8-methylenedioxylycoctonine-type alkaloids on the toxic effects associated with ingestion of tall larkspur (Delphinium spp) in cattle.

OBJECTIVE: To determine the contribution of 7,8-methylenedioxylycoctonine (MDL)-type alkaloids to the toxic effects of tall larkspur (Delphinium spp) consumption in cattle. ANIMALS: Sixteen 2-year-old Angus steers. PROCEDURES: Plant material from 3 populations of tall larkspur that contained different concentration ratios of MDL-type-to-N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids was collected, dried, and finely ground. For each plant population, a dose of ground plant material that would elicit similar clinical signs of toxicosis in cattle after oral administration was determined on the basis of the plants' MSAL-type alkaloid concentration. Cattle were treated via oral gavage with single doses of ground plant material from each of the 3 populations of tall larkspur; each animal underwent 1 to 3 single-dose treatments (> or = 21-day interval between treatments). Heart rate was recorded immediately before (baseline) and 24 hours after each larkspur treatment. RESULTS: Tall larkspur populations with a lower MDL-type-to-MSAL-type alkaloid concentration ratio required a greater amount of MSAL-type alkaloids to cause the expected clinical signs of toxicosis (including increased heart rate) in cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the typically less toxic MDL-type alkaloids contributed in a significant manner to the toxic effects of tall larkspur in steers. Consequently, both the concentration of MSAL-type alkaloids and the total concentration of MSAL- and MDL-type alkaloids should be determined when assessing the relative toxicity of tall larkspur populations. These results provide valuable information to determine the risk of toxicosis in cattle grazing on tall larkspur-infested rangelands.

Effects of larkspur (Delphinium barbeyi) on heart rate and electrically evoked electromyographic response of the external anal sphincter in cattle.

OBJECTIVE-To determine whether larkspur-derived N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids alter heart rate and electrically evoked electromyographic (eEMG) response of the external anal sphincter (EAS) in cattle and whether these effects can be reversed by acetylcholinesterase inhibitors. ANIMALS-12 beef heifers and 4 cows. PROCEDURES-3 or 4 heifers were used in 1 or 2 of 7 dose-response experiments; heart rate and EAS eEMG response were assessed before and 24 hours after oral treatment with larkspur (doses equivalent to 0.5 to 15 mg of MSAL-type alkaloids/kg). In 3 subsequent experiments, 3 heifers (1 of which was replaced with another heifer in the control experiment) each received 10 mg of MSAL-type alkaloids/kg and were injected IV with physostigmine (0.04 mg/kg), neostigmine (0.04 mg/kg), or saline (0.9% NaCl) solution 24 hours later, prior to assessment. Additionally, EAS eEMG response was measured in 4 cows before and after epidural administration of 2% lidocaine hydrochloride. RESULTS-Larkspur-treated heifers developed dose-related increases in heart rate and decreases in EAS eEMG response. Twenty-four hours after administration of MSAL-type alkaloids, neostigmine decreased heart rate but did not affect eEMG response, whereas physostigmine did not affect heart rate but caused a 2-fold increase in eEMG response. In cows, epidural anesthesia did not alter eEMG response, suggesting that transdermal stimulation of the EAS pudendal innervation did not occur. CONCLUSIONS AND CLINICAL RELEVANCE-In cattle, cardiac effects and muscle weakness or loss of EAS eEMG response induced by larkspur-derived MSAL-type alkaloids were reversed by neostigmine or physostigmine, respectively. Treatment with anticholinesterase inhibitors may alter the clinical effects of larkspur poisoning in cattle.

A QSAR toxicity study of a series of alkaloids with the lycoctonine skeleton.

A QSAR toxicity analysis has been performed for a series of 19 alkaloids with the lycoctonine skeleton. GA-MLRA (Genetic Algorithm combined with Multiple Linear Regression Analysis) technique was applied for the generation of two types of QSARs: first, models containing exclusively 3D-descriptors and second, models consisting of physicochemical descriptors. As expected, 3D-descriptor QSARs have better statistical fits. Physicochemical-descriptor containing models, that are in a good agreement with the mode of toxic action exerted by the alkaloids studied, have also been identified and discussed. In particular, TPSA (Topological Polar Surface Area) and nC=O (number of -C(O)- fragments) parameters give the best statistically significant mono- and bidescriptor models (when combined with lipophilicity, MlogP) confirming the importance of H-bonding capability of the alkaloids for binding at the receptor site.

Catastrophic cattle loss to low larkspur (Delphinium nuttallianum) in Idaho.

Low larkspur (Delphinium nuttallianum) is a toxic plant found on many western US rangelands. Episodes of fatal poisoning are often related to the abundance and toxicity of the low larkspurs. This report documents the fatal intoxication of 53 cattle in a herd of 404 animals in south-central Idaho during Spring 2002. Low larkspur had a toxic alkaloid concentration of 8.26 mg/g. Several factors were involved in a loss of this magnitude, including climatic conditions ideal for low larkspur growth, poor grass growth during the spring, the high alkaloid concentration in larkspur, and the deaths of many cattle while being moved from the pasture. It is important for livestock owners and managers to recognize toxic plants growing in their area. If there is an unusual abundance of larkspur or other toxic plants, correct identification can provoke caution in grazing management.

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.