T. Zane Davis

Toxicokinetics and pathology of plant-associated acute selenium toxicosis in steers

Sixteen of approximately 500 yearling steers died of acute selenium (Se) toxicosis after grazing on a Se-contaminated range for only a few days. Field studies and chemical analyses identified the predominant toxic plant as western aster (Symphyotrichum ascendens, previously Aster ascendens), which contained over 4,000 ppm Se (dry weight). Several dead animals that were necropsied had acute severe myocardial necrosis characterized by edema and myocyte swelling, with hypereosinophilia, clumping, and coagulation of myocardial proteins. Whole blood from 36 surviving steers was collected and analyzed, and 10 steers with elevated Se concentrations were selected for close monitoring and clinical evaluations. Each steer was weighed, and serum, blood, liver, skeletal muscle, and hair were regularly collected after removal from the Se-contaminated range. One animal that died 18 days after exposure was necropsied and exhibited severe multifocal myocardial fibrosis with extensive hepatic congestion, degeneration, and hemosiderosis. At 180 days postexposure, 2 of the 10 steers were euthanized, and tissue samples were collected. Both steers had rare, small fibrotic foci in their hearts. The Se elimination half-lives from serum, whole blood, liver, and muscle of the recovering steers were 40.5 ± 8.2, 115.6 ± 25.1, 38.2 ± 5.0, and 98.5 ± 19.1 days, respectively. The Se concentration in hair reached a peak of 11.5 ± 5.3 ppm at 22 days postexposure. The findings indicate that cattle are sensitive to acute Se toxicosis caused by ingestion of Se-accumulator plants, with myocardial necrosis as the primary lesion. Some poisoned animals may develop congestive heart failure weeks after the toxic exposure, and in the current study, Se was slowly excreted requiring a relatively long withdrawal time.

Serum elimination profiles of methyllycaconitine and deltaline in cattle following oral administration of larkspur (Delphinium barbeyi).

OBJECTIVE To describe the simple elimination kinetics of methyllycaconitine (MLA) and deltaline and evaluate the heart rate response in cattle following oral administration of larkspur. ANIMALS 5 healthy Angus steers that were habituated to metabolism crates. PROCEDURES Tall larkspur (Delphinium barbeyi) in the early flowering stage was collected, dried, and ground. Each steer received a single dose of larkspur that was equivalent to 10.4 mg of MLA/kg and 11.0 mg of deltaline/kg via oral administration. Steers were housed in metabolism crates during a 96-hour period following larkspur administration; heart rate was monitored continuously, and blood samples were collected periodically for analysis of serum MLA and deltaline concentrations as well as assessment of pharmacokinetic parameters. RESULTS No overt clinical signs of poisoning developed in any steer during the experiment. Mean +/- SE heart rate reached a maximum of 79.0 +/- 5.0 beats/min at 17 hours after larkspur administration. Serum MLA concentration was correlated directly with heart rate. Mean times to maximal serum concentration of MLA and deltaline were 8.8 +/- 1.2 hours and 5.0 +/- 0.6 hours, respectively. Mean elimination half-life values for MLA and deltaline were 20.5 +/- 4.1 hours and 8.2 +/- 0.6 hours, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Following larkspur administration in 5 healthy steers, maximum serum concentrations of MLA and deltaline were detected within 10 hours, and changes in serum MLA concentration and heart rate were correlated. Results indicated that cattle that have consumed larkspur will eliminate 99% of MLA and deltaline from serum within 144 hours.

Tremetone and Structurally Related Compounds in White Snakeroot (Ageratina altissima): A Plant Associated with Trembles and Milk Sickness

Ingestion of white snakeroot ( Ageratina altissima ) can cause trembles in livestock and milk sickness in humans. The toxicity has been associated with tremetol, a relatively crude, multicomponent lipophilic extract of the plant. In this study, 11 different compounds were isolated from white snakeroot-derived lipophilic extracts from 18 collections. Six of the isolated compounds have not been previously reported to be found in white snakeroot. High-performance liquid chromatography (HPLC) analysis indicated that there are three different chemotypes of white snakeroot from the plant samples analyzed. Elucidation of these chemotypes may explain the sporadic and unpredictable toxicity of white snakeroot to livestock and humans.

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.

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. Published in 2010 by John Wiley & Sons, Ltd.

Experimental Rayless Goldenrod (Isocoma pluriflora) Toxicosis in Goats

Rayless goldenrod (Isocoma pluriflora) sporadically poisons livestock in the southwestern United States. Similarities with white snakeroot (Ageratina altissima) poisoning and nearly identical chemical analyses led early researchers to conclude that tremetol, a mixture of benzofuran ketones, is the rayless goldenrod toxin. The toxicity of these ketone toxins have not been fully characterized nor are the pathogenesis and sequelae of poisoning completely understood. The objective of the current study was to characterize and describe the clinical and pathologic changes of rayless goldenrod toxicity in goats. Fifteen goats were gavaged with rayless goldenrod to obtain benzofuran ketone doses of 0, 10, 20, 40, and 60 mg/kg/day. After 7 treatment days, the goats were euthanized, necropsied, and tissues were processed for microscopic studies. After 5 or 6 days of treatment, the 40-mg/kg and 60-mg/kg goats were reluctant to move, stood with an erect stance, and became exercise intolerant. They had increased resting heart rate, prolonged recovery following exercise, and increased serum aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatinine kinase activities. All treated animals developed skeletal myopathy with dose-related distribution and severity. The goats dosed with 20 mg/kg and higher also developed myocardial degeneration and necrosis. Although skeletal myonecrosis was patchy and widely distributed, the quadriceps femoris was consistently damaged, even in low-dosed animals. Myocardial lesions were most severe in the papillary muscles of 60-mg/kg—dosed animals. This indicates that goats are highly susceptible to rayless goldenrod poisoning, and that the characteristic lesion of poisoning is skeletal and cardiac myonecrosis.

Differences in Ponderosa Pine Isocupressic Acid Concentrations Across Space and Time

Differences in Ponderosa Pine Isocupressic Acid Concentrations Across Space and Time DOI:10.2458/azu_rangelands_v32i3_cook

Livestock Poisoning With Pyrrolizidine-Alkaloid–Containing Plants (Senecio, Crotalaria, Cynoglossum, Amsinckia, Heliotropium, and Echium spp.)

Livestock Poisoning With Pyrrolizidine-Alkaloid–Containing Plants (Senecio, Crotalaria, Cynoglossum, Amsinckia, Heliotropium, and Echium spp.) DOI:10.2458/azu_rangelands_v31i1_Stegelmeier2

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

The Effect of Poisonous Range Plants on Abortions in Livestock

The Effect of Poisonous Range Plants on Abortions in Livestock DOI:10.2458/azu_rangelands_v31i1_welch