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Equine Toxicology

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  1. Equine Toxicology 2011 ANR Update Fernanda Camargo

  2. What is TOXICOLOGY? TOXICOLOGY is the science of Poisons A POISON is any solid, liquid, or gas that interferes with life processes. TOXIN: a poison that originates from biological processes. ALL SUBSTANCES ARE TOXIC: If you administer sufficient of any substance, you will kill any living thing [Paracelsus, early 1500s]. The DOSE determines the poison.

  3. Paracelsus “All things are poison and nothing is without poison, only the dose permits something not to be poisonous."

  4. Toxicology vs. Pharmacology • Same discipline on 2 different ends of the spectrum.

  5. Manifestation of Toxicosis • Toxicosis can impair any and all systems of the body • Cardiovascular system • Dermal system (Skin) • Gastrointestinal system • Hematic system • Hepatobiliary system • Musculoskeletal system • Nervous system • Reproductive system • Respiratory system • Urinary system • Sudden death

  6. Examples of Toxins/Poisons • Cardiovascular system: • Ionophores (Monensin, Rumensin): cattle feed additive • Tremetone (toxin found in white snakeroot) • Avocado • Skin: Turpentine, Mineral spirits, Phenols, Pine oils, Acids, Alkalies • GI Tract: diarrhea and colic • Blister beetles: alfalfa • Household and Industrial: Acids, alkalies, fertilizers, turpentine, etc • Hematic: anemia, hemorrhage, etc • Red maple, rodenticides • Liver: • alsike clover, red clover, mycotoxins

  7. Sources of Toxins: Hay • Alfalfa: Blister beetles (cantharidin)  diarrhea, colic, urinary tract blisters. • Hay Producers: • Blister beetles are not active when the first cutting is made in Kentucky • Blister beetles are attracted to blooms. Manage harvest intervals to minimize flowering of alfalfa or weeds in hay fields. Practice good broadleaf weed management. • Check hay fields for blister beetles before cutting from July through early September. They prefer blooming plants and tend to cluster in masses near field edges. Avoid areas where beetles are present.

  8. Sources of Toxins: Hay • Red clover: slaframine  Clovers can be an excellent source of nutrients but are associated with excessive salivation, oral ulcers, laminitis, colic, photosensitization and liver failure. • Alsike clover: photosensitization, hepatic encephalopathy, death.

  9. Sources of Toxins: Hay • Botulism: Round bales and silage

  10. Sources of Toxins: Hay • Stored wet: mold  heaves

  11. Sources of Toxins: Hay • Rough, mature: Impaction colic

  12. Sources of Toxins: Pasture • Endophyte Infected Tall Fescue: reproductive problems in pregnant mares • Prolonged gestation • Agalactia • Retained placenta • Dystocia • Weak foal

  13. Sources of Toxins: Supplements • Selenium: important anti-oxidant, but can be toxic if excessive. • Acute toxicity leads to death (oral and injectable supplements) • Chronic toxicity: hoof wall problems, hair loss

  14. Sources of Toxins: Concentrate • Rumensin(Ionophore antibiotics): cattle feed additive  increased milk production, increased weight gain, etc. Congestive heart failure in horses. • Mycotoxins: moldy grains  Leukoencephalomalacia • Salmonella: can cause diarrhea and endotoxemia

  15. Sources of Toxins: Ammoniated Feed and Nitrate/Nitrite • Silage or any ammoniated feed: Excess nitrogen  CNS toxicity • Nitrate/Nitrite: more common in ruminants  fertilizers and plants: CNS and methemoglobinemia • Nitrate-accumulating plants include: • Common Lambsquarter(Chenopodium album) • Redroot Pigweed (Amaranthusretroflexus) • Curly Dock (Rumexcrispus) • Sorghum-sudangrasses(Sorghum species).

  16. Sources of Toxins: Nitrate/Nitrite • There are several plants that are considered “Nitrate-Accumulating” plants. Animals that eat 0.05% of their body weight can be poisoned. Cattle are more susceptible. Fertilization, soil and drought conditions are factors in how high the nitrates are in plants. Some plants to watch out for include: • Corn • Pigweeds • Kochia • Russian Thistle • Lambsquarter • Sorghum/Sudan • Nightshades • Oat Hay

  17. Sources of Toxins: Pesticides • Herbicides, insecticides, fungicides, rodenticides • Organophosphates (CNS), organochlorines - DDT (CNS, sudden death), paraquat (respiratory, CNS), cholecalciferol rodenticide (cardiopathy), anti-coagulant rodenticides (bleeding)

  18. Source of Toxins: Plants • Most poisonous plants have an unpleasant taste: animals avoid. • However, if they have no choice but to eat these plants, they will develop a taste for them. • Herbicides often increase the palatability of plants by affecting the sugar content. Make sure you are cautious when grazing animals after herbicide applications. Avoid grazing treated areas until plants have dried, preferably waiting until plants are dead before introducing animals to the site.

  19. Source of Toxins: Plants • Cyanogenic: can lead to death  cherry trees (more toxic to ruminants than horses), sorghum, etc • Hemlock: tetanic seizures resembling strychnine.

  20. Source of Toxins: Plants • Black Locust: diarrhea and renal failure, weakness, dyspnea, tachycardia and depression, may be fatal.

  21. Source of Toxins: Plants • Black Walnut: shavings will cause laminitis (founder)

  22. Source of Toxins: Plants • Bracken Fern: Horses must consume a diet of 3-5% bracken fern for at least 30 days before clinical signs appear. Depression, muscle tremors, uncoordinated gait, hemorrhaging and bone marrow destruction.

  23. Source of Toxins: Plants • Oleander: Death within 12-24 hours, labored breathing, profuse sweating, colic, diarrhea (may or may not be bloody), shaking, erratic heart rate.

  24. Source of Toxins: Plants • Red Maple: dry leaves are deadly. Acute hemolytic disease: depression, icterus, anemia, hemoglobinemiaand hemoglobinuria. 

  25. Source of Toxins: Plants • Yew: This plant is highly toxic to herbivores.  As little as 6-8 ounces of fresh yew may kill an adult cow or horse. Acute onset and sudden death are common. Trembling, muscle weakness, dyspnea, arrhythmia, bradycardia, collapse.

  26. Source of Toxins: Plants • Cocklebur: cattle, swine and sheep are more sensitive than horses. GI inflammation, weakness, cardiac problems and death.

  27. Source of Toxins: Plants • Common Groundsel, Tansy Ragwort (Senecio): Horses and cattle are very sensitive. Lethargy, liver problems, weakness and death.

  28. Source of Toxins: Plants • Mustard: Consumption of mustard plants by mares causes Congenital Hypothyroid Dysmaturity Syndrome in foals. Signs include: 1. Abnormally long pregnancy 2. Foals commonly born with facial and lower jaw deformities 3. Deformities of the limbs • This syndrome occurs most often in mares in late pregnancy that are fed hay contaminated with mustard. Or when pastured in early spring in fields that contain mustard plants, such as Blue Mustard, Tumble Mustard, Flixweed, Shepherd’s-purse and Hoary Alyssum.

  29. Summary • Anything and Everything can be poisonous • Herbivores are less susceptible to common plant toxins than pets  the problem: they eat plants • Offer good quality hay and concentrate to the horses. • Only offer clean water • Don’t allow access to pesticides and cattle feed!!