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ARS Home » Pacific West Area » Logan, Utah » Poisonous Plant Research » Research » Research Project #424163

Research Project: Understanding and Mitigating the Adverse Effects of Poisonous Plants on Livestock Production Systems

Location: Poisonous Plant Research

2016 Annual Report

Objective 1: Develop and implement novel management protocols for establishing improved forage species on sites infested with known poisonous plants to reduce the risk of livestock mortality and morbidity, improve livestock performance, and improve rangeland resiliency and diversity. Specifically, develop science-based guidelines for grazing livestock on rangelands infested with Lupinus, Senecio, Delphinium and swainsonine and selenium-containing plants. Objective 2: Reduce the risks of livestock losses due to variations in quantitative and qualitative differences in toxin accumulation over time and plant species by quantifying the influence of endophytes, climate changes, and genotype on plant toxin accumulation (particularly swainsonine-containing plants and Delphinium and Lupinus species). Objective 3: Enhance feed and food safety by improving risk assessment and diagnosis of plant-induced poisoning to livestock by improving analytical methods for analyzing plant and animal tissues for toxins; measuring toxicokinetics, assessing carcinogenic and genotoxic potential, and identifying toxin metabolites and biomarkers of toxicoses. Objective 4: Develop improved procedures with guidelines for diagnostic and prognostic evaluation to reduce negative impacts of poisonous plants on livestock reproduction and embryo/fetal growth by improving early identification of poisoned animals, predicting poisoning outcomes, and management and treatment options through improved understanding of clinical, morphological and molecular alterations of plant-induced toxicosis. Objective 5: Develop guidelines to aid producers and land managers in making genetic-based herd management decisions to improve livestock performance and safety on grazed rangelands infested with poisonous plants through the use of identified animal genes, physiological pathways, and molecular mechanisms of action that underlie Conium, Cicuta, Delphinium, Lupinus, and Nicotiana, and other neurotoxic plant effects.

Livestock poisoning by plants results in over $503,000,000 lost to the livestock industry annually in the 17 western United States from death losses and abortions alone (Holechek, 2002). Plant poisonings extend worldwide to include 333 million poisonous plant-infested hectares in China and 60 million hectares in the central western region of Brazil, to name a few. There are over 6,000 species of pyrrolizidine alkaloid (PA)-containing plants, and over 350 individual PAs causing diseases in animals and humans have been identified. Economic losses are much larger as significant amounts of nutritious forage are wasted and management costs are increased due to the threat of toxic plant-related livestock losses. The Poisonous Plant Research Laboratory (PPRL) has provided worldwide leadership in poisonous plant research to the livestock industry and consumers including numerous solutions to toxic plant problems using an integrated, interdisciplinary approach (see Figure below). The research team investigates plant poisonings in a systematic matter by identifying the plant, describing the effects in animals, determining the toxin(s) and evaluating the mechanisms of action. The ultimate goal is to develop research-based solutions to reduce livestock losses from toxic plants. There are five coordinated objectives in this project plan providing guidelines for potential genetic-based management. This research will reduce livestock losses from plants and enhance the economic well-being of rural communities, improve rangeland health by combating invasive plant species, and help to provide safe animal products free from potential plant toxins for consumers.

Progress Report
Progress was made on all 5 objectives and their sub-objectives, all of which fall under National Program 215, Component I, Rangeland Management Systems to Improve Economic Viability and Enhance the Environment. ARS scientists and support staff at the Poisonous Plant Research Lab (PPRL) in Logan, Utah, made significant progress on all five basic objectives as outlined in the project plan: 1) identify plants that cause poisoning and describe the etiology of poisoning; 2) characterize the secondary compounds (toxins) through chemical analyses; 3) define how the toxins cause poisoning through toxicology and pharmacology studies; 4) improve diagnosis and prognosis of poisoning; and 5) develop strategies and management recommendations for livestock producers and land managers to reduce losses. Studies have been completed and published regarding the co-exposure of livestock to multiple poisonous plants. Death camas and low larkspur were the first plants to be evaluated as they often grow in the same habitats and cattle and sheep graze both as part of their diet. Initial results suggest that ingestion of multiple poisonous plants may exacerbate toxicity as one might expect, however results have also suggested that certain toxins affecting the same organ system may compete with each other thus reducing the effect of one toxin over another. Evaluation of improved perennial grass species and forage Kochia varieties to reduce and compete with invasive species is continuing. After 3 years of research on the Channeled Scablands of eastern Washington, it appears that successful establishment of perennial grass and kochia species will prevent reinvasion of annual grasses in both replicated plots and demonstration plots. The most successful grass species were Vavilov II (an improved Siberian wheat grass), Hycrest (an improved crested wheat grass), Sherman Big Blue (a native grass) and two forage Kochia varieties (Immigrant and Sahro) Evaluation of plots in the 4th year after establishment demonstrated that these species would competitively prevent reinvasion of cheat grass, medusahead rye and poisonous plants. Furthermore, after these plots were grazed by cattle, data suggested that forage quality and biomass was significantly improved. Last year two ranchers initiated larger scale plantings on their respective ranches and one rancher has implemented a five-year plan to improve his entire ranch using this information and technology. Cattle and sheep losses have continued to occur on mine reclamation sites where soils contain high levels of selenium. Recent feeding trials in sheep determined that reproductive performance is significantly reduced when sheep ingest forage containing levels of selenium above the nutritional requirements and ranchers will need to remove animals from these grazing sites well in advance of the breeding season. Greenhouse studies were recently completed and data suggests that certain soil amendments may successfully reduce the level of selenium taken up by forage plants. Analytical methods developed by ARS scientists at Logan, Utah, were used to detect pyrrolizidine alkaloids (PAs) in contaminated food and feed supplies. Further progress has been made on the National Institute of Health (NIH) funded PA research including large scale isolation and purification of epimeric lycopsamine and intermedine and synthesis and purification of their amine oxides (N-oxides). Analytical methods to screen herbal products for PAs have been completed. Echimidine was isolated from Echium vulgare and purified and the N-oxide synthesized. Three separate commercial samples of butterbur root powder (Petasites spp.), an herbal remedy, were screened for PAs and one contained two dehydropyrrolizidine alkaloids (DHPAs). Locoweed poisoning was studied in numerous animal models and ARS scientists found that large differences in sensitivity, disease progression, lesions and lesion distribution exist between animal species. Recent research indicates this is largely due to swainsonine’s affinity to a species' mannosidase enzymes. Additional comparisons of mannosidase expression in tissues and correlation of that expression with lesion development continue. Dose response studies of swainsonine poisoning have been completed in goats and initial results suggest goat susceptibility is similar to that of horses and greater than sheep and cattle. Studies comparing the lesions in the brain and eyes of multiple livestock species is continuing and publications are being prepared. Additional progress and new information to aid livestock producers and land managers in making genetic-based grazing decisions to improve livestock performance and safety on grazed rangelands infested with poisonous plants is continuing. Results from genome sequencing experiments have calculated that cattle susceptibility to larkspur is 90% heritable and one-third of the heritability can be attributed to a single candidate gene. Animal genes, physiological pathways, and molecular mechanisms of action that underlie the effects of neurotoxic plants such as lupine, larkspurs, and poison hemlock have been identified. Different cattle herds are being tested for resistance or sensitivity and individual animals are being selected using the gene based criteria. The current focus is to identify male and female individuals that express the resistant gene and cross breed them to determine the heritability of this trait. This research is a collaborative project with Clay Center, Nebraska.

1. The effect of co-administration of death camas (Zigadenus spp.) and low larkspur (Delphinium spp.) in cattle. In most rangeland settings livestock are potentially exposed to multiple poisonous plants containing multiple toxins. ARS scientists at Logan, Utah, studied the effects of co-administration of death camas and low larkspur in several livestock species. It was determined that combinations of toxic plants and their toxins acted synergistically or competitively depending on the toxin and the organ systems they affect. The results from these studies provide an increased knowledge and understanding regarding the acute toxicity of death camas and low larkspur in sheep and cattle. This information will be useful in further developing livestock management recommendations for ranchers.

2. Comparison of the serum toxicokinetics of larkspur toxins in cattle, sheep and goats. Larkspur plants (Delphinium spp.) are acutely toxic to cattle, and as such they cause a significant number of cattle death losses every year. ARS scientists in Logan, Utah, compared the serum toxicokinetic profiles of toxic larkspur alkaloids from D. barbeyi in cattle, goats, and sheep. Cattle and sheep are the two livestock species that are most often exposed to larkspur-infested rangelands, with cattle being more susceptible and sheep more resistant to larkspur toxicosis. Goats were also included, as goats are often used as a small ruminant model to study poisonous plants. It was determined that the increased resistance of goats and sheep to poisoning by larkspur could be due to differences in the toxicokinetics of the toxic larkspur alkaloids. This information will be used to evaluate risk when cattle graze larkspur.

3. Relative toxicity of the swainsonine-containing plants Ipomoea carnea and Astragalus lentiginosus in goats. The Brazilian plant Ipomoea carnea contains both the indolizidine alkaloid swainsonine and the nortropane alkaloids calystegines, whereas the U.S. locoweed A. lentiginosus contains only swainsonine. A dosing study was conducted by ARS scientists at Logan, Utah, in collaboration with Brazilian colleagues using goats to determine the relative contribution of swainsonine and calystegines to intoxication and resulting pathology in goats. The results of this study demonstrated that swainsonine contributed to the majority of the overt toxicity and histopathological lesions. Calystegines do not appear to be major toxins in livestock poisoning from Ipomoea carnea. This information is important to livestock producers in the U.S. and Brazil who graze animals on rangelands where Ipomoea carnea or locoweeds grow.

4. Consumption of larkspur by resistant and susceptible cattle. ARS scientists in Logan, Utah, screened cattle to provide groups of resistant and susceptible cattle to tall larkspur poisoning. Cattle were grazed on a larkspur-infested rangeland in southeastern Idaho during the summer for 2 years. Susceptible animals initially consumed more larkspur than did resistant animals both years, provoking clinical signs of intoxication. However, results at the end of the first summer trials showed there were few differences in larkspur consumption between resistant and susceptible cattle; in the latter portion of the second grazing trial, resistant steers consumed more larkspur than did susceptible steers, but with no fatalities. This information is important to livestock producers in the U.S. who graze animals on rangelands where larkspurs are an important component of the vegetation.

5. Neurological effects of water hemlock on animals. ARS scientists at Logan, Utah, completed a toxicology study of water hemlock (Cicuta spp.) in a cultured cell line. The pharmacological mechanism of action was identified and characterized. Interestingly, the toxic effects were reversed with two drugs used in human and veterinary medicine that prevent seizures (midazolam and benzodiazepine). This information is important in diagnosing and preventing water hemlock poisoning in animals.

6. Biological mechanism of piperidine alkaloids from poisonous plants. ARS scientists in Logan, Utah, compared the toxic effects of different piperidine alkaloid toxins from poisonous plants on neurological selected receptors. Specialized cell lines (TE-671 and SHSY-5Y cells) were used to understand and characterize the mechanism of action. These cells have fetal characteristics and were used to model crooked calf syndrome. This information will increase understanding why these plants cause birth defects and animal deaths.

7. Breed specific resistant to teratogenic lupine species. ARS scientists at Logan, Utah, demonstrated that breed differences exist in how cattle respond to plant toxins that cause birth defects. Pregnant Holstein heifers appear to eliminate the toxins faster and have lower serum concentrations of the lupine teratogen anagyrine than Angus heifers when dosed one time orally with ground lupines. Under these conditions, fetal movement in Angus heifers was inhibited more and longer than Holstein heifers. This information is important to livestock producers and scientists to select individual animals or breeds that may be resistant to plant poisoning.

8. The use of biomarkers to identify cattle resistant to poisoning by plants. ARS scientists from Logan, Utah, and Clay Center, Nebraska, identified resistant Angus bulls and Angus steers to the larkspur toxins. This was accomplished using a large DNA genotyping assay to identify specific genes for resistance. Angus bulls expressing the resistant genes were selected for progeny testing. This information will benefit ranchers in regions where larkspur and other neurotoxic plants infest the rangelands and will allow producers to make genetic-based grazing decisions to select replacement heifers and bulls for resistance and reduce cattle losses.

9. A survey of North American Astragalus and Oxytropis taxa for swainsonine (the locoweed toxin). A systematic examination for swainsonine in these species provided a definitive reference in regard to species containing swainsonine and is a valuable reference for land managers. ARS researchers in Logan, Utah, conducted a systematic examination of swainsonine in multiple species. Twenty-two Astragalus species representing ninety-three taxa and four Oxytropis species representing eighteen taxa were screened for swainsonine using chemical analytical techniques. Swainsonine was detected in forty-eight Astragalus taxa representing thirteen species and five Oxytropis taxa representing four species. The list of swainsonine-containing taxa reported here will serve as an essential reference for risk assessment and avoidance of livestock poisoning.

10. Seasonal variation of the toxins in low larkspur. The toxic alkaloids in Delphinium (larkspur) species are divided into two classes based on the chemical structures, i.e., highly toxic or moderately toxic. ARS researchers in Logan, Utah, studied alkaloid concentrations of low larkspur (D. nuttallianum) and found that alkaloid concentrations differed between vegetative and reproductive tissues. The vegetative tissues had significantly lower alkaloid concentrations than reproductive tissues. Understanding how alkaloid concentrations change at different stages of plant growth and different plant parts in a given larkspur species is important to developing management strategies to reduce livestock losses.

11. Effects of selenium on reproduction in sheep. ARS scientists in Logan, Utah, fed alfalfa pellets containing selenium concentrations to mimic that found in forages on certain soil sites. High levels of selenium in the diet resulted in decreased reproductive rates in sheep by up to forty percent. Lower conception rates and early embryonic loss during the first thirty days of gestation resulted. The information obtained from this study suggests that producers grazing in regions where forages are high in selenium should manage their flocks to avoid grazing these forages prior to or during the breeding season.

12. Monofluoroacetate in Palicourea and Arrabidaea species in South America. Several plant species in Brazil cause sudden death in cattle due to the toxic principle monofluoroacetate. ARS researchers in Logan, Utah, in collaboration with scientists in Brazil, reported for the first time that two species of Palicourea cause sudden death in cattle and contain monofluoroacetate. In addition, they corrected literature that a species of Arrabidaea previously reported to cause sudden death does not contain monofluoroacetate. A knowledge of taxa that contain monofluoroacetate will serve as reference for risk assessment and diagnostic purposes for livestock producers, fellow scientists and veterinarians.

13. A massive death loss in cattle fed weed infested alfalfa hay. ARS scientists in Logan, Utah, investigated a case of cattle poisoning in Colorado where 170 cows of a herd of over 500 died after feeding weed infested alfalfa hay. The cause of death was determined to be acute liver failure incident to unknown toxicosis. Subsequent liver biopsies of some of the survivors indicated significant liver damage had occurred in all cows ingesting the hay. ARS scientists used a bioassay guided chemical extraction process to identify the toxin and the poisonous plant in the hay. This research will provide important information to veterinarians for diagnosis and to livestock and hay producers to prevent poisonings in the future.

14. Improvement of rangelands in eastern Washington State infested with medusahead, cheatgrass and lupine. Vegetation on the Channeled Scablands of eastern Washington has been altered to a community dominated by medusahead, cheatgrass, lupine and other invasive weeds. Lupine is poisonous and causes crooked calf syndrome in cattle, and this problem is exacerbated by the invasion of annual grasses. ARS scientists in Logan, Utah, demonstrated that improved perennial grasses will establish in this region and will compete with and replace medusahead and cheatgrass, thus improve range conditions. These cool-season grasses will improve forage quality, increase forage production, reduce consumption of lupine and enhance the economic viability of the rural livestock producers in this region.

15. Protein supplementation enhances forage utilization by cattle on annual grass-dominated rangelands. The annual invasive grass, medusahead, has replaced much of the native vegetation on the Channeled Scablands of eastern Washington resulting in poor range conditions, reduced forage availability for cattle, increased consumption of poisonous weeds and a decline in productivity. ARS scientists in Logan, Utah, supplemented cattle with protein during the summer grazing months. The protein supplementation increased consumption of medusahead by cattle. Therefore, protein supplements can be used by livestock producers to increase utilization of medusahead and potentially reduce the consumption of poisonous plants.

16. Detection of pyrrolizidine alkaloids in herbal products. ARS scientists in Logan, Utah, completed the development of analytical methods to screen herbal products for the liver toxins, dehydropyrrolizidine alkaloids (DHPA’s). Large scale isolation of three major DHPA’s and their amine oxides (N-oxides) was completed. DHPA’s were detected in one of three commercially available herbal products (butterbur root powder (petasites spp.)). This is in addition to the detection of the multiple DHPA’s in many comfrey products commonly found in herbal remedies.

17. Poisoning in cattle from fiddleneck (Amsinckia spp.) in Arizona. Fiddleneck (Amsinckia spp.) contain the liver toxins, pyrrolizidine alkaloids (PA’s). A case of poisoning in cattle where over fifty cows died was reported to ARS scientists in Logan, Utah. They investigated the poisoning, collected and identified the suspect plants as Amsinckia, and performed chemical analyses on the plant material and tissues from the dead cows. Multiple PA’s were detected in the plant material and this was compared with fiddleneck collected in Washington State. This information was provided to the livestock producers and veterinarians with recommendations to prevent further losses.

18. Toxicity of pyrrolizidine alkaloids (PAs). Pyrrolizidine alkaloids (PAs) often contaminate feed, food, and medicinal or herbal products poisoning livestock, wildlife and humans. ARS scientists in Logan, Utah, previously demonstrated that riddelliine induced tumors at increased incidences regardless of dose or exposure duration and the type of tumor differed by exposure. ARS scientists also identified PA metabolites or adducts from livers of animals that were exposed to PAs providing information useful in identifying clinically poisoned animals. This research provides important information to animal and human health care providers.


Review Publications
Adrien, M.L., Gardner, D.R., Pfister, J.A., Marcolongo-Pereira, C., Riet-Correa, F., Schild, A.L. 2014. Conditioning food aversions to Ipomoea carnea var. Fistulosa in sheep. Ciência Rural. 44(2):362-367.
Beck, J.J., Porter, N., Cook, D., Griffith, C., Gee, W.S., Rands, A.D., Truong, T.V., Smith, L., San Roman, I. 2015. In-field volatile collection and analysis method utilizing a portable GC-MS: in situ headspace analysis of intact and damaged yellow starthistle flower heads. Phytochemical Analysis. 26:395-403.
Becker, M., Carneiro, F.M., Oliveira, L.P., Silva, M.I., Riet-Correa, F., Lee, S.T., Pescador, C.A., Nakazato, L., Colodel, E.M. 2016. Induction and transfer of resistance to poisoning by Amorimia pubiflora in sheep with non-toxic doses of the plant and ruminal content. Ciencia Rural. 46(4):674-680.
Brito, L.B., Albuquerque, R.F., Rocha, B.P., Albuquerque, S.S., Lee, S.T., Medeiros, R.M., Riet-Correa, F., Mendonca, F.D. 2016. Spontaneous and experimental poisoning of cattle by Palicourea aeneofusca in the region of Pernambuco and introduction of conditioned food aversion. Ciencia Rural. 46(1):138-143.
Brown, A.W., Stegelmeier, B.L., Colegate, S.M., Gardner, D.R., Panter, K.E., Knoppel, E.L., Hall, J.O. 2016. The comparative toxicity of a reduced, crude comfrey (Symphytum officinale) alkaloid extract and the pure, comfrey-derived pyrrolizidine alkaloids, lycopsamine and intermedine in chicks (Gallus gallus domesticus). Journal of Applied Toxicology. 36:716-725.
Brown, A.W., Stegelmeier, B.L., Colegate, S.M., Panter, K.E., Knoppel, E.L., Hall, J.O. 2015. Heterozygous P53 knockout mouse model for dehydropyrrolizidine alkaloid-induced carcinogenesis. Journal of Applied Toxicology. 35(12):1557-1563.
Carvalho, F.K., Cook, D., Lee, S.T., Taylor, C.M., Oliveira, J.B., Riet-Correa, F. 2016. Determination of toxicity in rabbits and corresponding detection of monofluoroacetate in four Palicourea (Rubiaceae) species from the Amazonas state, Brazil. Toxicon. 109:42-44.
Colegate, S.M., Boppre, M., Monzon, J., Betz, J.M., Panter, K.E. 2015. Pro-toxic dehydropyrrolizidine alkaloids in the traditional Andean herbal medicine "asmachilca". Journal of Ethnopharmacology. 172:179-194.
Colegate, S.M., Gardner, D.R., Betz, J.M., Fischer, O.W., Liede-Schumann, S., Boppre, M. 2016. Pro-toxic 1,2-Dehydropyrrolizidine alkaloid esters, including unprecedented 10-membered macrocyclic diesters, in the medicinally-used Alafia cf. caudata and Amphineurion marginatum (Apocynaceae: Apocynoideae: Nerieae and Apocyneae). Phytochemical Analysis. 27(5):257-276.
Collett, M.G., Stegelmeier, B.L., Tapper, B.A. 2014. Could nitrile derivatives of turnip (Brassica rapa) glucosinolates be hepato- or cholangiotoxic in cattle? Journal of Agricultural and Food Chemistry. 62(30):7370-7375.
Cook, D., Gardner, D.R., Lee, S.T., Pfister, J.A., Stonecipher, C.A., Welsh, S.L. 2016. A swainsonine survey of North American Astragalus and Oxytropis taxa implicated as locoweeds. Toxicon. 118:104-111.
Cook, D., Gardner, D.R., Pfister, J.A., Grum, D.S. 2014. Biosynthesis of natural products in plants by fungal endophytes with an emphasis on swainsonine. Recent Advances in Phytochemistry. 44:23-42.
Cook, D., Slominski, A., Gardner, D.R., Pfister, J.A., Irwin, R.E. 2016. Seasonal variation in the secondary chemistry of foliar and reproductive tissue of Delphinium nuttallianum. Biochemical Systematics and Ecology. 65:93-99.
Davis, T.Z., Stegelmeier, B.L., Lee, S.T., Green, B.T., Evans, T.J., Grum, D.S., Buck, S., Meyerholtz, K.A. 2016. White snakeroot poisoning in goats: Variations in toxicity with different plant chemotypes. Research in Veterinary Science. 106:29-36.
De Lima, F.G., Lee, S.T., Pfister, J.A., Miyagi, E.S., Costa, G.L., De Silva, R.D., Fioravanti, M.S. 2015. The effect of ensiling and haymaking on the concentrations of steroidal saponin in two Brachiaria grass species. Ciencia Rural. 45(5):858-863.
Duarte, A.L., Medeiros, R.M., Carvalho, F.K., Lee, S.T., Cook, D., Pfister, J.A., Costa, V.M., Riet-Correa, F. 2014. Induction and transfer of resistance to poisoning by Amorimia (Mascagnia) septentrionalis in goats. Journal of Applied Toxicology. 34(2):220-223.
Galbraith, M.L., Vorachek, W.R., Estill, C.T., Whanger, P.D., Bobe, G., Davis, T.Z., Hall, J.A. 2016. Rumen microorganisms decrease bioavailability of inorganic selenium supplements. Biological Trace Element Research. 171(2):338-343.
Gardner, D.R., Cook, D. 2016. Analysis of swainsonine and swainsonine N-oxide as trimethylsilyl derivatives by Liquid Chromatography-Mass Spectrometry and their relative occurrence in plants toxic to livestock. Journal of Agricultural and Food Chemistry. 64(31):6156-6162.
Golo, P.S., Gardner, D.R., Grilley, M.M., Takemoto, J.Y., Krasnoff, S., Pires, M.S., Fernandes, E.K., Bittencourt, V.R., Roberts, D.W. 2014. Production of destruxins from metarhizium spp. fungi in artificial medium and in endophytically colonized cowpea plants. PLoS One. 9(8):e104946.
Gotardo, A.T., Pfister, J.A., Raspantini, P.C., Gorniak, S.L. 2016. Maternal ingestion of Ipomoea carnea: Effects on goat-kid bonding and behavior. Toxins. 8(3):74.
Green, B.T., Brown, D.R. 2016. Interactions between bacteria and the gut mucosa: Do enteric neurotransmitters acting on the mucosal epithelium influence intestinal colonization or infection? Advances in Experimental Medicine and Biology. 874:121-141.
Green, B.T., Goulart, C., Welch, K.D., Pfister, J.A., Mccollum, I.J., Gardner, D.R. 2015. The non-competitive blockade of GABAA receptors by an aqueous extract of water hemlock (Cicuta douglassi) tubers. Toxicon. 108:11-14.
Green, B.T., Lee, S.T., Welch, K.D., Cook, D., Kem, W.R. 2016. Activation and desensitization of peripheral muscle and neuronal nicotinic acetylcholine receptors by selected, naturally-occurring pyridine alkaloids. Toxins. doi: 10.1016/j.toxicon.2015.09.015.
Green, B.T., Lee, S.T., Welch, K.D., Gardner, D.R., Stegelmeier, B.L., Davis, T.Z. 2015. The serum concentrations of lupine alkaloids in orally-dosed Holstein cattle. Research in Veterinary Science. 100:239-244.
Green, B.T., Panter, K.E., Lee, S.T., Welch, K.D., Pfister, J.A., Gardner, D.R., Stegelmeier, B.L., Davis, T.Z. 2015. Differences between Angus and Holstein cattle in the Lupinus leucophyllus induced inhibition of fetal activity. Toxicon. 106:1-6.
Lima, E.F., Medeiros, R.M., Cook, D., Lee, S.T., Kaehler, M., Santos-Barbosa, J.M., Riet-Correa, F. 2016. Studies in regard to the classification and putative toxicity of Fridericia japurensis (Arrabidaea japurensis) in Brazil. Toxicon. 115:22-27.
Lopes, J.R., Riet-Correa, F., Cook, D., Pfister, J.A., Medeiros, R.M. 2014. Elimination of the tremorgenic toxin of Ipomoea asarifolia by milk. Pesquisa Veterinaria Brasileira. 34(11):1085-1088.
Maia, L.A., Macedo Pessoa, C.R., Rodrigues, A.F., Colegate, S.M., Dantas, A.M., Medeiros, R.T., Riet-Correa, F. 2014. Duration of an induced resistance of sheep to acute poisoning by Crotalaria retusa seeds. Ciência Rural. 44(6):1054-1059.
Mott, I.W., Cook, D., Lee, S.T., Stonecipher, C.A., Panter, K.E. 2016. Phylogenetic examination of two chemotypes of Lupinus leucophyllus. Biochemical Systematics and Ecology. 65:57-65.
Nascimento, E.M., Medeiros, R.M., Lee, S.T., Riet-Correa, F. 2014. Poisoning by Poiretia punctata in cattle and sheep. Pesquisa Veterinaria Brasileira. 34(10):963-966.
Oliveira, C.A., Riet-Correa, G., Lima, E., Leite, D.M., Pfister, J.A., Cook, D., Riet-Correa, F. 2015. Feeding preferences of experienced and naïve goats and sheep for the toxic plant Ipomoea carnea subsp. fistulosa. Ciencia Rural. 45(9):1634-1640.
Oliveira, C.A., Riet-Correa, G., Tavares, C., Souza, E., Cerqueira, V.D., Pfister, J.A., Cook, D., Riet-Correa, F. 2014. Conditioned food aversion to control poisoning by Ipomoea carnea subsp. fistulosa in goats. Ciencia Rural. 44(7):1240-1245.
Panter, K.E., Welch, K.D., Gardner, D.R., Green, B.T. 2013. Poisonous plants: Effects on embryo and fetal development. Birth Defects Research Part C: Embryo Today: Reviews. 99:223-234.
Pfister, J.A., Green, B.T., Welch, K.D., Provenza, F.D., Cook, D. 2016. Impacts of toxic plants on the welfare of grazing livestock. In:Villalba, J.J., editor. Animal Welfare in Extensive Production Systems. Sheffield, U.K.:5m Publishing. p. 78-102.
Pfister, J.A., Panter, K.E., Lee, S.T., Moterram, E. 2014. Crude protein supplementation to reduce lupine consumption by pregnant cattle in the scablands of eastern Washington. International Journal of Poisonous Plant Research. 3(1):26-32.
Rincon, D.F., Diaz, G.J., Gardner, D.R. 2016. Detection of Ptaquilosides in different phenologic stages of Bracken fern (Pteridium aquilinum) and analysis of milk samples in farms with hematuria in Tolima, Colombia. Revista de Medicina Veterinaria. 11(1):72-77.
Rocha, B.P., Reis, M.O., Driemeier, D., Cook, D., Camargo, L.M., Riet-Correa, F., Evencio-Neto, J., Mendonca, F.S. 2016. Liver biopsy as diagnostic method for poison¬ing by swainsonine-containing plants. Pesquisa Veterinaria Brasileira. 36(5):373-377.
Silva Negreiros Neto, T.D., Gardner, D.R., Hallwass, F., Jessica Matias Leite, A., Guimaraes De Ameida, C., Nunes Silva, L., Araujo Roque, A.D., Gobbi De Bietncourt, F., Guimaraes Barbosa, E., Tasca, T., Jose Macedo, A., Veira De Almeida, M., Brandt Giordani, R. 2016. Activity of pyrrolizidine alkaloids against biofilm formation and Trichomonas vaginalis. Biomedicine and Pharmacotherapy. 83:323-329.
Stewart, W.C., Whitney, R.R., Scholljegerdes, E.J., Naumann, H.D., Cherry, N.M., Muir, J.P., Lambert, B.T., Walker, J.W., Adams, R.P., Welch, K.D., Gardner, D.R., Estell, R.E. 2015. Effects of juniperus species and stage of maturity on nutritional, in vitro digestibility, and plant secondary compound characteristics. Journal of Animal Science. 93(8):4034-4047.
Stonecipher, C.A., Panter, K.E., Villalba, J.J. 2016. Effect of protein supplementation on forage utilization by cattle in annual grass-dominated rangelands in the Channel Scablands of Eastern Washington. Journal of Animal Science. 94(6):2572-2582.
Welch, K.D., Cook, D., Green, B.T., Gardner, D.R., Pfister, J.A., Mcdaneld, T.G., Panter, K.E. 2015. Adverse effects of larkspur (Delphinium spp.) on cattle. Agriculture. 5:456-474.
Welch, K.D., Gardner, D.R., Green, B.T., Stonecipher, C.A., Cook, D., Pfister, J.A. 2016. Comparison of the serum toxicokinetics of larkspur toxins in cattle, sheep and goats. Toxicon. 119:270-273.
Welch, K.D., Green, B.T., Gardner, D.R., Cook, D., Pfister, J.A. 2015. The effect of administering multiple doses of tall larkspur (Delphinium barbeyi) to cattle. Journal of Animal Science. 93(8):4181-4188.
Welch, K.D., Green, B.T., Gardner, D.R., Stonecipher, C.A., Pfister, J.A., Cook, D. 2016. The effect of co-administration of death camas (Zigadenus spp.) and low larkspur (Delphinium spp.) in cattle. Toxins. doi: 10.3390/toxins8010021.
Welch, K.D., Lee, S.T., Panter, K.E., Gardner, D.R. 2014. A study on embryonic death in goats due to Nicotiana glauca ingestion. Toxicon. 90:64-69.
Welch, K.D., Parsons, C., Gardner, D.R., Deboodt, T., Shreder, P., Cook, D., Pfister, J.A., Panter, K.E. 2015. Evaluation of the seasonal and annual abortifacient risk of western juniper trees on Oregon rangelands: Abortion risk of western juniper trees. Rangelands. 37(4):139-143.