Toxic plants are a concern in equine management as they pose health risks to horses when ingested. These plants contain various compounds that can lead to adverse effects ranging from mild discomfort to severe illness or death. Horses may encounter toxic plants in pastures, hay, or during foraging. Common toxic plants include ragwort, yew, and oleander, each containing specific toxins that affect equine physiology differently. Understanding the identification, distribution, and toxicological impact of these plants is important for prevention and management. This page compiles peer-reviewed research studies and scholarly articles that explore the identification, toxic mechanisms, and management strategies of toxic plants in relation to equine health.
Pfister JA, Stegelmeier BL, Cheney CD, Gardner DR.Locoweed species (Astragalus and Oxytropis spp.) are a serious toxic plant problem for grazing livestock. Horses and sheep have been conditioned to avoid eating locoweed using the aversive agent LiCl. The objective of this study was to determine if previous locoweed intoxication affects food aversion learning in horses and sheep. Horses and sheep were divided into 3 treatment groups: control (not fed locoweed and not averted to a novel feed); locoweed-novel feed averted (fed locoweed and averted to a novel feed); and averted (not fed locoweed and averted to a novel feed). Animals in the locowe...
Johnson AL, Divers TJ, Freckleton ML, McKenzie HC, Mitchell E, Cullen JM, McDonough SP.Fourteen horses at a boarding stable in Virginia were diagnosed with hepatic disease and locally grown hay was implicated as the cause. Objective: Panicum dichotomiflorum, the predominant grass species in the hay, is hepatotoxic to horses. Methods: Naturally occurring cases were adult horses of various breeds. Two healthy adult horses and 2 healthy adult sheep were used in feeding trials. Methods: Blood and liver specimens collected from affected animals during the outbreak were analyzed. Some of the affected animals were treated supportively; the main intervention was hay withdrawal. Feeding ...
Binev R, Valchev I, Nikolov J.Monitoring of changes in some blood laboratory parameters in 34 horses after ingesting freshly harvested maize that was to be used for ensiling, heavily contaminated with young Datura stramonium plants, is described. For a 7-day period the following parameters were monitored: haemoglobin content (HGB), red blood cell counts (RBC), white blood cell counts (WBC), haematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), differential white cell counts (DWC), erythrocyte sedimentation rate (ESR), protein fractions, aspa...
Gerber R, Naudé TW, de Kock SS.Two out of a group of 23 mares exposed to tef hay contaminated with Datura ferox (and possibly D. stramonium) developed colic. The 1st animal was unresponsive to conservative treatment, underwent surgery for severe intestinal atony and had to be euthanased. The 2nd was less seriously affected, responded well to analgesics and made an uneventful recovery. This horse exhibited marked mydriasis on the first 2 days of being poisoned and showed protracted, milder mydriasis for a further 7 days. Scopolamine was chemically confirmed in urine from this horse for 3 days following the colic attack, whil...
Alward A, Corriher CA, Barton MH, Sellon DC, Blikslager AT, Jones SL.Ingestion of wilted red maple leaves by horses can result in severe hemolytic anemia and methemoglobinemia. Little is known about what factors influence the outcome of red maple leaf toxicosis in horses. Objective: Our hypothesis was that physical examination findings, clinicopathologic variables or therapeutic modalities may predict outcome in horses with red maple leaf toxicity. Methods: Horses with red maple leaf toxicosis presented to referral hospitals in the southeast region of the United States. Methods: A multi-institutional retrospective study was designed to identify factors that pre...
Finno CJ, Valberg SJ, Wünschmann A, Murphy MJ.To determine clinical signs, diagnostic findings, tissue tremetone concentrations, and clinical outcome or postmortem findings in horses evaluated for acute severe nonexertional rhabdomyolysis initially attributed to white snakeroot toxicosis. Methods: Retrospective case series. Methods: 14 horses. Methods: Records of the University of Minnesota Veterinary Medical Center or Diagnostic Laboratory were searched from 1998 to 2005. Inclusion criteria included serum creatine kinase (CK) activity > 45,000 U/L, severe nonexertional myonecrosis of proximal postural muscles at necropsy, or signs of wea...
Kite GC, Stoneham CA, Veitch NC, Stein BK, Whitwell KE.Liquid chromatography-mass spectrometry (LC-MS) analysis of methanol extracts of Oenanthe crocata roots revealed that oenanthotoxin co-eluted with another major polyalkyne, 2,3-dihydro-oenanthotoxin, using the existing high performance liquid chromatography (HPLC) method (isocratic elution from C18 with aqueous methanol) for investigating Oenanthe poisoning. Positive ES or APCI gave [(M+H)-H(2)O](+) and its methanol adduct as major ion species for oenanthotoxin, whereas 2,3-dihydro-oenanthotoxin formed [M+H](+) and its methanol adduct. The two polyalkynes could be chromatographically resolved ...
Naudé TW, Gerber R, Smith RJ, Botha CJ.Datura poisoning of horses is extensively reviewed. An outbreak of intractable impaction colic affecting 18 of 83 horses was stopped by withdrawing dried tef hay contaminated with young Datura plants. The dried, botanically identified Datura stramonium and D. ferox contained respectively 0.15% mass/mass (m/m) hyoscyamine as well as 0.16% m/m hyoscine (scopolamine) and only hyoscine at a concentration of 0.11% m/m. Immature, unidentifiable plants resembling D. stramonium, contained 0.14% m/m and 0.12% m/m of the 2 respective tropane alkaloids. The outbreak was characterised by protracted and re...
Tiwary AK, Puschner B, Kinde H, Tor ER.A 2-year-old bay Thoroughbred colt was found dead overnight in its stall without a known history of any illness, existing disease, or toxicant exposure. No information on the clinical signs before this animal's death was reported. A full necropsy was performed the next morning and revealed a mild to moderate degree of endocardial hemorrhages in both ventricles. Microscopic examination of the heart showed an acute mild multifocal necrosis of papillary muscles and ventricles. The stomach content contained approximately 2% Taxus alkaloids as determined by gas chromatography/mass spectrometry. In ...
Rohner Mächler M, Glaus TM, Reusch CE.In a Bearded Collie with acute weakness, hematemesis, melena, painful abdomen and pale mucous membranes a hematocrit of 13% and panhypoproteinemia were found. This combination of findings was the manifestation of severe gastrointestinal bleeding. Despite intensive laboratory and imaging investigations no systemic or local cause could be identified. After repeated client interrogation it was found that the dog had been receiving a food supplement for equines. It was further detected that this supplement besides a shell extract also contained willow (Salicaceae) and meadowsweet (Filipendula, Spi...
Cope RB, Camp C, Lohr CV.Despite the well-founded reputation of plants of the genus Taxus as being amongst the most toxic plants for domestic livestock in the US, there are surprisingly few published case reports of yew poisoning in horses. This report documents 2 acute fatalities in horses in the central Willamette Valley, OR associated with the consumption of Taxus sp. The predominant features of the intoxication were peracute death, with no signs of struggling or convulsions, in otherwise fit and well managed adult horses. The most significant gross necropsy findings were limited to pulmonary congestion and hemorrh...
Tukov FF, Rimoldi JM, Matthews JC.Repin, a major constituent in extracts of the plant Centaurea repens is thought to be the active principal responsible for the development of equine nigropallidal encephalomalacia (ENE), a fatal Parkinson-like neurodegenerative disorder in horses. Although the exact mechanism by which ingestion of this weed causes ENE is uncertain, a limited body of experimental evidence suggests a critical role for the glutathione redox system. In the present study, the mechanism of repin neurotoxicity was examined in PC12 cells with a focus on determining the role of glutathione (GSH) in repin-induced mitoch...
Woods LW, Filigenzi MS, Booth MC, Rodger LD, Arnold JS, Puschner B.Three horses died as a result of eating grass hay containing summer pheasant's eye (Adonis aestivalis L.), a plant containing cardenolides similar to oleander and foxglove. A 9-year-old thoroughbred gelding, a 20-year-old appaloosa gelding, and a 5-year-old quarter horse gelding initially presented with signs of colic 24-48 hours after first exposure to the hay. Gastrointestinal gaseous distension was the primary finding on clinical examination of all three horses. Two horses became moribund and were euthanatized 1 day after first showing clinical signs, and the third horse was euthanatized af...
Carmalt J, Rosel K, Burns T, Janzen E.Thirty-four mixed breed horses from two separate farms showed signs of abdominal discomfort, pyrexia and dehydration after being exposed to a new batch of 14% complete horse feed. A new batch of cattle feed from the same manufacturer resulted in dairy cows showing depression, a drop in milk production and diarrhoea. Examination of both diets revealed the presence of white kidney beans (Phaseolus vulgaris). Inclusion of raw beans of this genus in animal feeds is to be avoided.
Forrester MB, Stanley SK.A portion of calls handled by poison centers involve poisonings of animals; however, information on such calls is limited. This study used data from poison centers in Texas collected during 1998-2002 to document the epidemiology of animal poisoning calls. There were a total of 24,467 animal poisoning calls, representing 2.0% of all calls. Dogs were affected in 87% of the calls and cats in 11%. The exposures were unintentional in 99% of the cases, occurred via ingestion in 95% and involved dermal exposure in 5% of the cases. Exposures occurred at the owner's own residence 91% of the time and we...
Pfister JA, Stegelmeier BL, Gardner DR, James LF.Spotted locoweed (Astragalus lentiginosus var. diphysus) is a toxic, perennial plant that may, if sufficient precipitation occurs, dominate the herbaceous vegetation of pinyon-juniper woodlands on the Colorado Plateau. Six cow/calf pairs and four horses grazed a 20-ha pasture with dense patches of locoweed in eastern Arizona during spring 1998. Locoweed density was 0.7 plants/m2 in the pasture. Locoweed averaged 30.4% NDF and 18.4% CP. Concentrations of the locoweed toxin, swainsonine, fluctuated from 1.25 to 2 mg/g in locoweed. Horses ate more (P < 0.01) bites of locoweed than did cows (15...
Loretti AP, Colodel EM, Gimeno EJ, Driemeier D.This study reports a neurological disease unrecognised until now in ponies in southern Brazil. Objective: Epidemiological data strongly suggests that the ingestion of Sida carpinifolia is involved in the aetiology. We tested the hypothesis that it is an acquired lyosomal storage disease. Methods: Following the death of 3 ponies, all ponies from the premises were closely monitored; epidemiological data and clinical findings carefully recorded. Fragments of several organs, including CNS, were fixed in neutral formalin and embedded in paraffin-wax. Sections were stained with haematoxylin and eosi...
Botha CJ, Naudé TW.Well-known plant poisonings such as 'dunsiekte' (seneciosis) and 'jaagsiekte' (crotalariosis) of horses in southern Africa are briefly reviewed. Relatively unfamiliar mycotoxicoses such as stachybotryotoxicosis and perennial rye grass staggers and potentially occurring exotic intoxications such as equine nigropallidal encephalomalacia and ergot alkaloid poisoning are also discussed. This article is aimed at informing the southern African equine practitioner about probable poisonings that might occur locally in horses.
Dirikolu L, Hughes C, Harkins D, Boyles J, Bosken J, Lehner F, Troppmann A, McDowell K, Tobin T, Sebastian MM, Harrison L, Crutchfield J, Baskin SI....The epidemiological association between black cherry trees and mare reproductive loss syndrome has focused attention on cyanide and environmental cyanogens. This article describes the toxicokinetics of cyanide in horses and the relationships between blood cyanide concentrations and potentially adverse responses to cyanide. To identify safe and humane blood concentration limits for cyanide experiments, mares were infused with increasing doses (1-12 mg/min) of sodium cyanide for 1 h. Infusion at 12 mg/min produced clinical signs of cyanide toxicity at 38 min; these signs included increased heart...
McGorum BC, Anderson RA.To test the hypothesis that equine grass sickness may be associated with the ingestion of cyanogenic glycosides from white clover (Trifolium repens), the concentrations of whole blood cyanide, and plasma and urinary thiocyanate, the main metabolite of cyanide, were measured in 12 horses with acute grass sickness and 10 horses with subacute grass sickness, and in 43 control horses, of which 21 were co-grazing with cases of acute grass sickness, 12 grazed pastures where grass sickness had not been reported, and 10 were stabled horses. The healthy horses which grazed with cases of acute grass sic...
Copetti MV, Santurio JM, Boeck AA, Silva RB, Bergermaier LA, Lubeck I, Leal AB, Leal AT, Alves SH, Ferreiro L.This article reports an outbreak of intoxication of female horses with Claviceps purpurea in southern Brazil. The outbreak affected twelve pregnant mares which were fed with black oat (Avena strigosa) during the pre-delivery period. Underdevelopment of the mammary gland in the pre-delivery period resulting in post-delivery agalactia was the most pronounced finding. These mares delivered weak and unviable foals, which showed no suckling reflex and died within a few hours of birth. Laboratory analysis of oat samples fed to the animals resulted in the identification of Claviceps purpurea scleroti...
Pfister JA, Stegelmeier BL, Cheney CD, Ralphs MH, Gardner DR.Locoweed (Oxytropis sericea) is a serious poisoning problem for horses grazing on infested rangelands in the western United States. Our objectives were to determine 1) whether lithium chloride or apomorphine would condition aversions to palatable foods, and at what doses, and 2) whether horses could be averted to fresh locoweed in a pen and grazing situation. Apomorphine was not an acceptable aversive agent because at the dose required to condition an aversion (> or = 0.17 mg/kg BW), apomorphine induced unacceptable behavioral effects. Lithium chloride given via stomach tube at 190 mg/kg BW...
Barr AC, Reagor JC.Horses poisoned by a plant may show a myriad of clinical signs. Awareness of the poisonous plants growing in a given area and those that are likely to appear in hay and their associated clinical signs can be instrumental in making diagnoses. More importantly, the information can be shared with clients to help prevent plant poisonings in horses.
Lee ST, Stegelmeier BL, Gardner DR, Vogel KP.Switchgrass (Panicum virgatum L.) has been reported to be hepatotoxic, causing photosensitization in lambs and horses. In this study we show the presence of steroidal saponins in two samples of switchgrass that has been implicated in the poisonings of sheep and horses. After hydrolysis of the saponins, diosgenin was determined to be the major sapogenin in both switchgrass samples. We also confirmed the presence of diosgenin in kleingrass after hydrolysis of saponins extracted from it.
Miyazaki S, Fukumura M, Yoshioka M, Yamanaka N.From 1997 to 1999, 29 cases of disorders were detected in cattle and horses that had been fed ryegrass straw imported from the U.S.A. These animals showed symptoms resembling ryegrass staggers and the clinical signs disappeared after removal of the straw. Endophytic hyphae were detected in the seeds of all straw samples that were responsible for the clinical cases. Lolitrem B concentrations in the straw ranged between 972 and 3740 ppb. Ergovaline concentrations were between 355 and 1300 ppb. Even though the concentrations of lolitrem B were lower than the toxic threshold proposed by Oregon Sta...
Pessoa CR, Pessoa AF, Maia LA, Medeiros RM, Colegate SM, Barros SS, Soares MP, Borges AS, Riet-Correa F.The effects and susceptibility of donkeys to Crotalaria juncea and Crotalaria retusa poisoning were determined at high and low doses. Seeds of C. juncea containing 0.074% of dehydropyrrolizidine alkaloids (DHPAs) (isohemijunceines 0.05%, trichodesmine 0.016%, and junceine 0.008%) were administered to three donkeys at 0.3, 0.6 and 1 g/kg body weight (g/kg) daily for 365 days. No clinical signs were observed and, on liver and lung biopsies, the only lesion was a mild liver megalocytosis in the donkeys ingesting 0.6 and 1 g/kg/day. Two other donkeys that received daily doses of 3 and 5 g seed/...
Thomsen ME, Davis EG, Rush BR.A 5-y-old Paint horse gelding was evaluated for acute laminitis after exposure to black walnut shavings. The gelding's feet were previously soaked in an ice bath continuously for approximately 24 h. Treatment consisted of anti-inflammatory and vasodilator therapy. Serial radiographs revealed progressive palmar deviation of the third phalanx and subsolar abscesses in both forefeet. The gelding developed purulent discharge from the right coronary band and the hoof wall detached circumfrentially. Euthanasia was elected after 54 days. Continual exposure of the gelding's feet to ice water temperatu...
Nicholson SS.Grasses that are essential components of livestock grazing programs sometimes are the source of tremorgenic toxicants to the animals consuming them. Morbidity can be high but mortality need not be if management closely observes the cattle daily and removes them at first sign of trouble. Specific treatment generally is not available nor needed. Survivors recover completely within a few days or weeks, except in chronic phalaris poisoning, where sheep and cattle may die after prolonged illness--or at least not make an economical recovery. Certain poisonous plants are responsible for tremorgenic s...
Sanders SG, Tucker RL, Bagley RS, Gavin PR.Magnetic resonance imaging (MR) was used to make a diagnosis of equine nigropallidal encephalomalacia in a horse. Equine nigropallidal encephalomalacia is a neurodegenerative disease that has many characteristics with Parkinson-like diseases in humans. Historically, horses were euthanized based on clinical signs and exposure to the toxic weed, yellow star thistle (Centaurea solstitialis). Previously, the disease has only been confirmed on necropsy. MR imaging can provide accurate and sensitive visualization of typical lesions seen in the brain of horses affected with equine nigropallidal encep...
Bony S, Durix A, Leblond A, Jaussaud P.The toxicokinetics of ergovaline (an ergopeptine mycotoxin present in some grasses infected with endophytic fungus of the genus Neotyphodium) were studied after intravenous administration of a single dose of 15 microg/kg bwt in four gelding horses. Plasma ergovaline concentrations were measured by high performance liquid chromatography, and the kinetic data were described by a three-compartment model. The elimination half-life and the total clearance of ergovaline were found to be 56.83 +/- 13.48 min and 0.020 +/- 0.004 L/min x kg, respectively. According to the toxicological data previously r...
Locke KB, McEwan DR, Hamdorf IJ.Horses and cattle fed swainsona (Swainsona canescens var horniana) over a period of 8 to 10 weeks lost condition and became incoordinated and hypersensitive. Histological examination of tissues from affected animals revealed the characteristic changes of widespread cellular vacuolation and axonal spheroids in the CNS. Cattle withdrawn from the toxic plant after being fed for varying periods up to 8 weeks returned to normal. Serum alpha-mannosidase activity declined significantly in cattle during the test period, whereas in horses that activity rose. Serum alkaline phosphatase levels increased ...
Woods LW, Filigenzi MS, Booth MC, Rodger LD, Arnold JS, Puschner B.Three horses died as a result of eating grass hay containing summer pheasant's eye (Adonis aestivalis L.), a plant containing cardenolides similar to oleander and foxglove. A 9-year-old thoroughbred gelding, a 20-year-old appaloosa gelding, and a 5-year-old quarter horse gelding initially presented with signs of colic 24-48 hours after first exposure to the hay. Gastrointestinal gaseous distension was the primary finding on clinical examination of all three horses. Two horses became moribund and were euthanatized 1 day after first showing clinical signs, and the third horse was euthanatized af...
Forrester MB, Stanley SK.A portion of calls handled by poison centers involve poisonings of animals; however, information on such calls is limited. This study used data from poison centers in Texas collected during 1998-2002 to document the epidemiology of animal poisoning calls. There were a total of 24,467 animal poisoning calls, representing 2.0% of all calls. Dogs were affected in 87% of the calls and cats in 11%. The exposures were unintentional in 99% of the cases, occurred via ingestion in 95% and involved dermal exposure in 5% of the cases. Exposures occurred at the owner's own residence 91% of the time and we...
Raisbeck MF, Dahl ER, Sanchez DA, Belden EL, O'Toole D.A review of Wyoming State Veterinary Laboratory records for 1947-1987 revealed no substantiated cases of naturally occurring selenosis. However, older reports attributed thousands of animal deaths to selenium each year in this area. Beginning in August 1988, cases of suspected selenosis and selenium deficiency were solicited from veterinarians and producers by announcements in various statewide livestock publications. As of August 1991, 4 cases (all horses) of naturally occurring selenosis have been confirmed. Clinical signs were most often referable to epithelial damage, e.g., hoof lesions an...
Pfister JA, Stegelmeier BL, Cheney CD, Ralphs MH, Gardner DR.Locoweed (Oxytropis sericea) is a serious poisoning problem for horses grazing on infested rangelands in the western United States. Our objectives were to determine 1) whether lithium chloride or apomorphine would condition aversions to palatable foods, and at what doses, and 2) whether horses could be averted to fresh locoweed in a pen and grazing situation. Apomorphine was not an acceptable aversive agent because at the dose required to condition an aversion (> or = 0.17 mg/kg BW), apomorphine induced unacceptable behavioral effects. Lithium chloride given via stomach tube at 190 mg/kg BW...
Gerber R, Naudé TW, de Kock SS.Two out of a group of 23 mares exposed to tef hay contaminated with Datura ferox (and possibly D. stramonium) developed colic. The 1st animal was unresponsive to conservative treatment, underwent surgery for severe intestinal atony and had to be euthanased. The 2nd was less seriously affected, responded well to analgesics and made an uneventful recovery. This horse exhibited marked mydriasis on the first 2 days of being poisoned and showed protracted, milder mydriasis for a further 7 days. Scopolamine was chemically confirmed in urine from this horse for 3 days following the colic attack, whil...
Minnick PD, Brown CM, Braselton WE, Meerdink GL, Slanker MR.An aqueous extract of the heartwood of black walnut (Juglans nigra) was given via stomach tube to 10 horses. Eight developed Obel grade 3 or 4 laminitis within 12 hr. Limb edema and mild sedation were the only other clinical signs observed. One horse was euthanized due to severe signs. The other 7 recovered within 6 days. Gas chromatography/mass spectrometry of aqueous extracts of heartwood, bark and nuts of black walnut identified juglone in the bark and nuts, but not in the heartwood. It was concluded that the aqueous extract of heartwood is laminogenic to horses, but the active ingredient i...
Ossedryver SM, Baldwin GI, Stone BM, McKenzie RA, van Eps AW, Murray S, Fletcher MT.Three ponies continuously grazed a pasture containing an estimated 24% Indigofera spicata (wet weight basis) for 4-6 weeks in April and May 2004. They developed ataxia, paresis, depression, muscle fasciculations, dysphagia, ptyalism and halitosis. Two also developed corneal opacity. One pony recovered with supportive treatment, but the other two were euthanased and necropsied. Neuropathology was not present in either case, but both livers had periacinar and periportal lymphocytic infiltrations and hydropic degeneration of mid-zonal hepatocytes, with mild to moderate periacinar necrosis also ev...
Abutarbush SM.The objective of this observational study is to describe clinical, haematological and serum biochemical findings of horses affected with alfalfa dodder (Cuscuta campestris) toxicity. Twenty horses naturally exposed to alfalfa dodder toxicity were examined and information was collected on history and clinical signs. Physical examination was done on horses in the premises (n=20), and venous blood samples of 12 horses were submitted for haematology and serum biochemical examination for each horse. Abnormal clinical signs started around 36 hours after horses were fed the contaminated alfalfa. Abno...
Agrawal K, Ebel JG, Altier C, Bischoff K.The leaves of Acer rubrum (red maple), especially when wilted in the fall, cause severe oxidative damage to equine erythrocytes, leading to potentially fatal methemoglobinemia and hemolytic anemia. Gallic acid and tannins from A. rubrum leaves have been implicated as the toxic compounds responsible for red maple toxicosis, but the mechanism of action and toxic principle(s) have not been elucidated to date. In order to investigate further how red maple toxicosis occurs, aqueous solutions of gallic acid, tannic acid, and ground dried A. rubrum leaves were incubated with contents of equine ileum,...
Petzinger E.Pyrrolizidine alkaloids belong to a class of phytotoxins which are present in more than 6000 plant species. The disease seneciosis in farm animals represents the severe poisoning by pyrrolizidine alkaloids from plants of the genus Senecio. This form of poisoning has been known since the end of the 19th century in Germany, the USA, Canada and New Zealand, and is mainly caused by Senecio jacobaea and related Senecio spp. in farm animals, including poultry. Animal poisoning by pyrrolizidine alkaloids is of worldwide importance. In Germany poisoning of horses and cattle by Senecio jacobaea, which ...
Pfister JA, Stegelmeier BL, Gardner DR, James LF.Spotted locoweed (Astragalus lentiginosus var. diphysus) is a toxic, perennial plant that may, if sufficient precipitation occurs, dominate the herbaceous vegetation of pinyon-juniper woodlands on the Colorado Plateau. Six cow/calf pairs and four horses grazed a 20-ha pasture with dense patches of locoweed in eastern Arizona during spring 1998. Locoweed density was 0.7 plants/m2 in the pasture. Locoweed averaged 30.4% NDF and 18.4% CP. Concentrations of the locoweed toxin, swainsonine, fluctuated from 1.25 to 2 mg/g in locoweed. Horses ate more (P < 0.01) bites of locoweed than did cows (15...
Galey FD, Whiteley HE, Goetz TE, Kuenstler AR, Davis CA, Beasley VR.Twelve light horse geldings developed laminitis within 8 to 12 h of being dosed by nasogastric tube with an aqueous extract of black walnut (Juglans nigra). Four of the 12 horses developed the severe signs of grade 3 laminitis (lame at a walk, refused to lift feet). Laminitis was accompanied by mild depression and limb oedema. There was no evidence of shock or colic. The horses developed neutropenia by 4 h after dosing with the extract, which shifted to a relative neutrophilia by 8 to 12 h. Minimal increases in plasma epinephrine and cortisol concentrations were suggested in severely affected ...
Mount ME, Feldman BF.Strychnine toxicosis is characterized by inducible tetanic seizures and metaldehyde poisoning by fine fasciculations progressing to generalized tremors and seizures. Intoxication with 1080 causes seizures, random running movements, vomiting, defecation, urination, acidosis and hyperglycemia. Intoxication with rodenticides causing coagulopathy is characterized by hemorrhage into body cavities but not necessarily external hemorrhage. Anticholinesterase insecticides cause salivation, urination and defecation, while chlorinated hydrocarbon insecticides cause CNS disturbances. Ethylene glycol intox...
Nobre D, Dagli ML, Haraguchi M.Twenty horses died 30 d after being fed a diet containing 40% of tritured Crotalaria juncea seeds. Before death, they had staggering, dyspnea and fever. At necropsy the most evident lesions were areas of lung parenchyma consolidation and enlarged and congested livers. Histopathological examination revealed diffuse fibrosing alveolitis with hyaline membranes, suggesting a blood-borne insult, and passive congestion in the liver with compression of the hepatocyte trabecules. To confirm the diagnosis, guinea pigs were given 60% of a commercial diet + 40% tritured C juncea seeds. After 4 mo of feed...
Geor RJ, Becker RL, Kanara EW, Hovda LR, Sweeney WH, Winter TF, Rorick JK, Ruth GR, Hope E, Murphy MJ.Fever, limb edema, and laminitis were observed in horses 18 to 36 hours after they consumed hoary alyssum (Berteroa incana) under field and experimental conditions. Clinical signs were not observed in all horses that had ingested the plant. Diagnosis in the field cases was limited to observation of clinical signs and evidence of plant ingestion in hay or on pasture. In most cases, clinical remission was observed 2 to 4 days after empirical treatment, removal of the plant source, or both.
Fletcher MT, Hayes PY, Somerville MJ, De Voss JJ.Crotalaria medicaginea has been implicated in horse poisoning in grazing regions of central-west Queensland, which resulted in the deaths of more than 35 horses from hepatotoxicosis in 2010. Liver pathology was suggestive of pyrrolizidine alkaloidosis, and we report here the isolation of two previously uncharacterized pyrrolizidine alkaloids from C. medicaginea plant specimens collected from pastures where the horses died. The first alkaloid was shown by mass spectometric and NMR analyses to be 1β,2β-epoxy-7β-hydroxy-1α-methoxymethyl-8α-pyrrolizidine, which, like other alkaloids previousl...
