Stephen T. Lee

Larkspur poisoning: toxicology and alkaloid structure-activity relationships

Abstract Systematic approaches to taxonomic classifications of the tall larkspur spp. have been developed using traditional chemical methods to profile alkaloids, comparison of relative toxicity of individual alkaloids, plant morphology/taxonomy and molecular genetics. Using these methods (papers published in this series) toxicology of three distinct species of tall larkspurs including Delphinium glaucum, Delphinium barbeyi and Delphinium occidentale is described. Tall larkspurs (Delphinium spp.) continue to be the most serious cause of cattle losses on mountain rangelands in the western US. Over 40 norditerpenoid alkaloids have been reported in species of larkspurs and toxicology data on 25 of these have been reported by the authors. These alkaloids can be classified into three general types based on their structural characteristics and toxicity: the N-(methylsuccinyl) anthranoyl lycoctonine (MSAL)-type, having high toxicity; the lycoctonine-type, with moderate toxicity; and the 7,8-methylenedioxylycoctonine (MDL)-type, of low toxicity. The structural importance of the methylsuccinimido anthranilic acid ester group at the C18 position is evident in the high toxicity of MSAL alkaloids, particularly methyllycaconitine (MLA), Nudicauline (NUD) and 14-deacetylnudicauline (14-DAN). Other structural aspects of these alkaloids such as the C14 functionality are also important, as demonstrated by the reduced toxicity of barbinine. MLA is the alkaloid of most importance in toxicity of larkspurs on mountain rangelands because of its prevalence in most larkspurs and high toxicity. While NUD and 14-DAN also possess high toxicity, they are relatively minor components in few larkspur species (generally the plains and low larkspurs), but when present at concentrations approaching 1xa0mg/g dry weight they contribute significantly to overall toxicity. Deltaline (DLT) is often found in high concentrations in many larkspurs but because of low toxicity, its contribution to larkspur poisoning in the field is relatively minor and it will probably not cause toxicosis in the absence of the MSAL-type alkaloids.

Cattle Consumption of Velvet Lupine (Lupinus leucophyllus) in the Channel Scablands of Eastern Washington

Abstract Certain lupines (Lupinus spp.) contain alkaloids that cause contracture-type skeletal birth defects and cleft palate (“crooked calf syndrome”) when consumed by cows during the 40th to 70th day of gestation. The objective of this study was to determine when cattle graze velvet lupine (Lupinus leucophyllus Dougl.) during its phenological development, and whether this period overlaps the critical period of gestation. Grazing studies were conducted in 2001, 2002, and 2003 in the same 100 ha pasture in eastern Washington. A second objective was addressed in 2001 to determine if cows with crooked calves consumed more lupine than cows with normal calves. Five mature Hereford cows with crooked calves at their side and 6 mature Hereford cows with normal calves grazed together for the summer. There was no difference (Pu2009=u20090.17) in the amount of lupine consumed between groups, and all cows consumed some lupine. In 2002, 10 3-year-old Hereford cows with normal calves were used, and in 2003, 8 of the same cows from the 2002 study with normal calves were used. In all 3 years, cows started consuming lupine in July and August after annual grasses dried and annual forbs matured. Lupine is a deep-rooted perennial that remained green and succulent longer into the summer than the associated forages. Concentration of the teratogenic alkaloid anagyrine declined as lupine seeds shattered in late June and early July. Lupine consumption occurred during the critical period of gestation in 2 of the 3 years, but no crooked calves were produced. Apparently, the cows did not ingest sufficient amounts of anagyrine over the susceptible period of time to produce crooked calves. The management recommendation for this site is to restrict access to lupine during July when cattle begin to graze lupine and anagyrine levels may still be relatively high. Once the seeds shatter, toxicity greatly declines.

The effect of body condition on serum concentrations of two teratogenic alkaloids (anagyrine and ammodendrine) from lupines (Lupinus species) that cause crooked calf disease.

Several species of lupine (Lupinus spp.) are toxic to livestock, causing death losses in sheep and cattle but more commonly crooked calf disease in pregnant range cows. The major toxic alkaloids in lupine are of the quinolizidine alkaloid group and include the teratogen anagyrine, which is primarily responsible for crooked calf disease. Lupines also contain teratogenic piperidine alkaloids including ammodendrine. Previous work in sheep has shown that lupine alkaloid clearance may be influenced by the animals physiological status. Therefore, the purpose of this study was to determine if differences in body condition of cattle would alter the absorption and elimination of anagyrine or ammodendrine given in a single oral dose as Lupinus leucophyllus or Lupinus sulphureus, respectively. Mature non-lactating cows in low body condition (LBC, n = 4) and high body condition (HBC, n = 4) received a single dose of dry ground lupine plant (2.0 g/kg of BW) via oral gavage. Lupinus leucophyllus (anagyrine) was dosed first; then after 21 d the same animals were dosed with L. sulphureus (ammodendrine). Blood samples were taken via jugular venipuncture 0 to 60 h after dosing. Serum anagyrine and ammodendrine concentrations were evaluated. The concentration of anagyrine was greater (P = 0.001) in the HBC group and peaked 2 h after dosing versus 12 h in LBC cows. Similarly for ammodendrine, the alkaloid concentration peaked at 3 h after dosing for the HBC group compared with 6 h for the LBC group (P = 0.001). Area under the curve tended to differ (P <or= 0.11) for both alkaloids in the HBC group compared with the LBC group. There were also differences in the maximum serum anagyrine (P = 0.02) and ammodendrine (P = 0.06) concentrations. Elimination half-life (E1/2) tended to differ (P = 0.12) between the HBC and LBC groups for ammodendrine. The kinetic profiles suggest that body condition influenced the disposition of these alkaloids. This study also suggests that body condition may impact the risk of toxicity, teratogenicity, or both of these alkaloids.

A swainsonine survey of North American Astragalus and Oxytropis taxa implicated as locoweeds.

Swainsonine, an indolizidine alkaloid with significant physiological activity, is an α-mannosidase and mannosidase II inhibitor that causes lysosomal storage disease and alters glycoprotein processing. Swainsonine is found in a number of plant species worldwide, and causes severe toxicosis in livestock grazing these plants, leading to a chronic wasting disease characterized by weight loss, depression, altered behavior, decreased libido, infertility, and death. Swainsonine has been detected in 19 Astragalus and 2 Oxytropis species in North America by thin layer chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry and a jack bean α-mannosidase inhibition assay. In addition, 5 species in North America are presumed to contain swainsonine based upon reports from field cases. Many of these plant species have not been analyzed for swainsonine using modern instrumentation such as gas or liquid chromatography coupled with mass spectrometry. To provide clarification, 22 Astragalus species representing 93 taxa and 4 Oxytropis species representing 18 taxa were screened for swainsonine using both liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. Swainsonine was detected in 48 Astragalus taxa representing 13 species and 5 Oxytropis taxa representing 4 species. Forty of the fifty-three swainsonine-positive taxa had not been determined to contain swainsonine previously using liquid or gas chromatography coupled with mass spectrometry. The list of swainsonine-containing taxa reported here will serve as a reference for risk assessment and diagnostic purposes.

Influence of grazing pressure on cattle consumption of the teratogenic plant velvet lupine

ABSTRACT Lupine species may contain teratogenic alkaloids that cause birth defects called crooked calf syndrome. If pregnant cows ingest toxic lupine between d 40 and 100 of gestation, fetal movement is impaired and irreversible skeletal defects occur. To prevent ingestion of this toxic forb during the critical period of gestation, there is a need to determine the time and conditions in which cattle graze velvet lupine (Lupinus leucophyllus Dougl. ex Lindl.). Intensive grazing trials were conducted to evaluate cattle consumption of lupine in its stages of phenological development through the growing season, in relation to increasing grazing pressure in eastern Washington. Ten Hereford cows and a bull grazed velvet lupine-infested rangeland in 3 grazing pressure trials each year. Pastures were fenced to limit forage availability to the amount required for 6-d trials in 2007 and 10-d trials in 2008. Diets were estimated by bite count. Linear and quadratic regression was used to describe the relationship between forage allowance (the reciprocal of grazing pressure) and lupine consumption. In May, cattle preferred green cheatgrass (Bromus tectorum L.) and immature forbs at the beginning of the trial and did not graze lupine until all other forage was depleted. There was a negative linear relationship between declining forage allowance and increasing lupine consumption (r 2 xa0= 0.91 and 0.78 for 2007 and 2008, respectively). In June, cheatgrass was dry and cattle preferred forbs that were flowering. As availability of palatable forbs declined, cows started eating lupine, and this declined as its availability declined. Quadratic regressions were not strong (r 2 xa0= 0.10 and 0.53 for 2007 and 2008, respectively). In July when annual forbs matured and became fibrous and unpalatable, cattle ate lupine at the beginning of the trial and reverted to dry cheatgrass as lupine became limited. There was a quadratic regression in 2007 (r 2 xa0= 0.37) and a positive linear regression in 2008 (r 2 xa0= 0.69). We conclude that lupine is not palatable early in the growing season in May and early June, but cattle can be forced to graze it as availability of green cheatgrass and other forbs declines. Intensive grazing systems that force cattle to use all forage may enhance the risk of crooked calf disease by forcing cattle to graze lupine throughout the grazing season.

The effect of intermittent dosing of Nicotiana glauca on teratogenesis in goats

Sustained inhibition of fetal movement in livestock species, induced by several poisonous plants, can result in numerous skeletal-contracture malformations. Lupines are responsible for a condition in cattle referred to as crooked calf syndrome that occurs when pregnant cattle graze teratogenic lupines. Similar malformations are also seen in animals poisoned by Conium maculatum (coniine) and Nicotiana glauca (anabasine). A proposed management strategy to limit these types of birth defects includes utilizing an intermittent grazing schedule to allow short durations of grazing lupine-infested areas interrupted by movement to a lupine-free pasture. The objective of this study was to use a goat model to determine if an intermittent schedule of five continuous days on treatment followed by two days off treatment would be sufficient to decrease, or prevent, the incidence of anabasine-induced malformations. The data from this study suggest that, for N. glauca in goats, the intermittent grazing program of five days exposure with two days of non-exposure is insufficient to prevent significant skeletal malformations from occurring. However, this study did demonstrate an inverse relationship between the amount of serum anabasine in the dam and the extent of fetal movement.

Effects of Experience and Lactation on Lupine Consumption by Cattle

Abstract Lupines (Lupinus spp.) are widespread range plants that are often toxic to livestock. Some reports suggest that naïve, younger animals might consume more lupine than more experienced, older cattle. Further, lactational stress might alter forage selection, and lactating cows might eat more lupine than nonlactating cows. Thus, the objectives of these trials were to examine the influence of experience and lactation on lupine intake. Both study areas were near Ritzville, Washington, on rangeland dominated by cheatgrass or downy brome (Bromus tectorum L.), with abundant velvet lupine (Lupinus leucophyllus Dougl.). During the first trial, six naïve and six experienced Hereford cows were grazed together for 25 d during summer. There was no difference (Pu200a>u200a0.5) in consumption of lupine by naïve and experienced cows. Consumption peaked at 10%–14% of daily bites. During the second trial, six lactating and six nonlactating cows grazed a lupine-infested pasture for 18 d. There was no difference (Pu200a>u200a0.6) in consumption between lactating and dry cows. Lupine consumption gradually increased and peaked at 10%–15% of the diets. Our results suggest that experience and lactation status are probably minor considerations in livestock management schemes to reduce losses to lupine.

A Screen for Swainsonine in Select North American Astragalus Species

Swainsonine is found in several plant species worldwide, and causes severe toxicosis in livestock grazing these plants, leading to a chronic condition characterized by weight loss, altered behavior, depression, decreased libido, infertility, and death. Swainsonine has been detected in 13 North American Astragalus species of which eight belong to taxa in four taxonomic sections, the Densifolii, Diphysi, Inflati, and Trichopodi. These sections belong to two larger groups representing several morphologically related species, the Pacific Piptolobi and the small‐flowered Piptolobi. The objective of this study was to screen the other 31 species for swainsonine in sections Densifolii, Diphysi, Inflati, and Trichopodi previously not known to contain swainsonine. Furthermore, to broaden the scope further, 21 species within the 8 sections of the Pacific Piptolobi and the small flowered Piptolobi were screened for swainsonine. Swainsonine was detected for the first time in 36 Astragalus taxa representing 29 species using liquid and gas chromatography coupled with mass spectrometry. Several taxonomic sections were highly enriched in species that contain swainsonine while others were not. A systematic examination for swainsonine in these species will provide important information on the toxic risk of these species and may be a valuable reference for diagnosticians and land managers.

A study on embryonic death in goats due to Nicotiana glauca ingestion.

Numerous plants are known to be teratogenic in livestock. In addition to causing malformations, several plants can also cause embryonic death. These losses decrease the reproductive efficiency of animals exposed to these plants. The aim of this study was to determine if teratogenic plants such as lupines or tobaccos cause embryonic losses. A goat model using the plant Nicotiana glauca was used in this study, as this model has been used to characterize the mechanism of Lupinus, Conium, and Nicotiana-induced terata. Four groups of goats were dosed from gestational day 1-10, 11-20, 21-30, and 31-40. Goats were evaluated via ultrasound imaging for pregnancy after completion of the dosing regimen and kids were evaluated for malformations at the time of parturition. Overall, there was no evidence from this study that N. glauca (anabasine) at this dose (2 g/kg/day) would cause embryonic losses in goats. However, the dose of N. glauca used in this study was at the lower threshold that would be expected to produce terata. Therefore it is possible that higher doses of anabasine could cause embryonic loss. Further work is also needed to characterize the kinetic profile of anabasine, and other teratogenic alkaloids, in the fetal compartments.

Selected Poisonous Plants Affecting Animal and Human Health

Plant-associated toxins can be synthesized by the plant, produced by associated microorganisms, or simply incorporated and accumulated by the plant. These toxins are found in nearly all plants, many of which are generally considered “safe” to use as feed and food. Some are potent carcinogens. Others only cause mild inconvenience, such as tainted milk or replacement and loss of other desirable forages. Toxin concentrations and subsequent plant toxicity also vary between plants and even within populations, and between seasons and years. This variation in some situations is related to environmental conditions, but often the cause is unknown. This variation makes it difficult to predict toxicity and subsequent risk of poisoning. Most intoxications affect grazing livestock and wildlife; however, human and companion animal poisoning also occurs. This is generally due to plant or toxin contamination of prepared feeds, food, medicines, and herbal products. The objectives of this chapter are to introduce some common toxic plants and describe some of the pathologic changes relating to their poisoning in animals and humans, with a focus on livestock intoxication.