Poisonous Weeds And Toxic Factors In Hay Crops: Why You Should Worry Birgit Puschner Veterinary Toxicologist [email protected] School of Veterinary Medicine, UC Davis Overview of Today’s Talk • When to suspect a poisoning • Toxic plants: • Nitrate accumulators • Pyrrolizidine alkaloids • Oleander • Grasses that cause mechanical irritation Factors Contributing to Poisoning • Animal • Plant • Sensitive species • Palatable? • Adaptation to tolerate • Right time of the year? toxic plants is possible à concentrations of • What other feed is toxins vary with season available? • Does the plant remain • Unable to avoid toxic toxic when dried? plant (i.e. in hay cubes) Resources • Textbooks: • A Guide to Plant Poisoning of Animals in North America: by A.P. Knight and R.G. Walter, 1st edition, 2001. Teton NewMedia. www.tetonnm.com • UCANR publication: http://anrcatalog.ucdavis.edu/pdf/8398.pdf Detailed publication on Livestock-poisoning Plants of California (link on CERE under Lab resources) • Websites (with images and location) • https://www.ars.usda.gov/pacific-west- area/logan-ut/poisonous-plant- research/docs/poisonous-plants-by-toxic- syndrome/ • http://plants.usda.gov/about_plants.html Nitrate/Nitrite Accumulators • Sorghum spp (Sudan grass, Johnson grass) • Pigweed (Amaranthus retroflexus) • Lamb’s-quarters (Chenopodium album) • Alfalfa, oat, corn, nightshades (Solanum) Chenopodium album Pigweed Johnson grass Sudan grass Orchard Grass Hay 5,900 ppm Nitrate Pigweed Sudan Hay 18,800 ppm Nitrate Amaranthus retroflexus Nitrate/Nitrite – Mechanism • Only ruminants and pseudoruminants are susceptible • Nitrate in plants à converted to toxic nitrite • Nitrite à methemoglobin • Methemoglobin: incapable of Oxygen transport à Anoxia NO3/NO2 – Clinical signs • Acute syndrome: – Onset within 1/2 - 4 hours after feeding – GI irritation, difficulty breathing, tremors, ataxia – Rapid, weak heart beat – Convulsions, death in 6 - 24 hours – Abortions, esp. in the last trimester • Chronic syndrome: significance unclear – Results of field observations, not reproduced experimentally – Abortions (most often 3 - 5 days after exposure) Nitrate – Diagnosis • Clinical history and chemical analysis – Lots of deaths – Change in feed / new hay – Hungry animals • Samples – Multiple forage samples – not uniform – Eyeballs – intact – frozen – Serum or blood – Water – rare Nitrate/Nitrite – Plants • Factors increasing NO3 concentration: – Heavy fertilization; application of 2,4 D – Decreased soil moisture/drought – Decreased light – Frost – Highest concentration just prior to flowering – Plant diseases: leaf rust, mildew, root rot • Dry plants retain NO3 • Highest concentration in stems NO3/NO2 – Prevention • Forage: – Analyze suspect forage before feeding – Identify weeds and evaluate their potential for nitrate accumulation – Wait as long as possible before harvesting – Cut late in the day on a sunny day – Careful use of nitrogen fertilizer – Avoid harvesting stems – raise cutter bar above 6 inches Interpreting Nitrate Forage Tests (differing reporting units) Feeding NO3 (dry matter) NO3-N (dry matter) KNO3 (dry matter) Recommendations < 5,000 ppm < 1,200 ppm < 8,100 ppm Generally Considered (0.5%) (0.12%) (0.81%) Safe for Livestock > 5,000 ppm > 1,200 ppm > 8,100 ppm Caution: Problems (0.5%) (0.12 %) (0.81%) can occur at this level but but but < 10,000 ppm < 2,300 ppm < 16,000 ppm (1%) ppm (0.23%) (1.62%) >10,000ppm (1%) > 2,300 ppm >16,200ppm Do not feed (1.62%) Pyrrolizidine Alkaloid Containing Plants Common groundsel – Senecio vulgaris Pyrrolizidine Alkaloids • Found in 3 major plant families: – Compositae (Senecio) – Fabaceae (Crotolaria) – Boraginaceae (Amsinckia, Cynoglossum) • Common in the Pacific NW and CA • Common invaders of pastures and hayfields, and open woodlands Common Groundsel – Senecio vulgaris Senecio vulgaris Common Groundsel S. vulgaris in alfalfa hay (white seed heads, fluffy) ALFALFA HAY Sowthistle Common groundsel (look alike, (toxic) but non- PA-contaminated Alfalfa Pellets Fiddlenecks– Amsinckia spp. Tansy Ragwort – Senecio jacobaea PAs Toxicity • Liver activation of PAs to toxic pyrroles à hepatic disease • Susceptibility: – pigs > poultry > cattle, horses >>>>> sheep, goats • Horses and cattle: – 5 – 10% of bw in a few days or weeks à acute liver disease – Most common: small amounts over several months to reach a total dosage of 25 – 50% of bw à chronic liver disease – Reluctant to eat plants, but do so if in hay – Unavoidable in pellets PAs – Clinical Signs • Liver disease: Icterus, depression, anorexia – Most commonly observed after chronic exposure (often 2 – 8 months after 1st exposure) – Horses: acute onset of head pressing, aimless pacing, chewing, ataxia, yawning, drowsiness, diarrhea or constipation – Cattle: subacute onset of decreased appetite and milk production, followed by weight loss, weakness, recumbency • Neuro signs in horses are a result of hepatic encephalopathy • Often secondary (hepatogenous) photosensitization PAs - Diagnosis • Plant ID of hay • Testing of feed for PAs • Get detailed feeding history (new shipments, cuttings of hay, location of grower, etc) • Chemistry panel: no pathognomonic changes • Pathological findings (lesions, chronicity) • Rule-out of other causes for liver disease PAs – Treatment • No effective treatment – Effects are cumulative à often advanced, irreversible damage to liver when noticed • Supportive care questionable • Consider euthanasia of clinically affected animals • In horses: bile acids may provide useful prognostic indicator • Prevention – Avoid exposure to PAs – recognize PA plants or submit for ID – Avoid contamination of hay with PA plants Pyrrolizidine Alkaloids – What to do? • Identify suspect weeds • If ID not possible à analysis for PAs • No safe dose for horses and cattle • Sheep and goats: can tolerate the plants • Weed control Case: Sudden death in heifers • 75 heifers on 100 acres (Coulterville) • Fed hay • 4/6/12: • 3 animals found dead in the AM • Cows were fine the night before • Sick cows: lethargic with diarrhea • Field necropsy: nothing remarkable, 8 mo pregnant, bloody around eye and rectum (buzzards) Hay fed to cows Diagnosis – Oleander Poisoning Identification of Chemical analysis leaves in ingesta of serum, urine, ingesta C:\Xcalibur\data\OLE\0107-06 01/07/01 11:14:47 AM Oleandrin 0.025 ug/ml, 20 ul=0.5ng MeOH RT: 0.00 - 14.98 SM: 15G RT: 5.58 NL: 7. 50 E4 MA: 16 9 18 3 2 m/ z = 10 0 354.5-355.5+372.5-373.5 90 Oleandrin F: + c ESI Full ms3 [email protected] 80 [email protected] [ 115. 0 0 - 6 0 0 . 0 0 ] MS 70 RT: 5.6 min 0107-06 60 50 40 Rel ati ve Abundance 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (min) 0107-06#210-232 RT: 5.28-5.79 AV: 23 SB: 45 4.55-5.05, 6.00-6.52 NL: 4.69E4 F: + c ESI Full mS3 [email protected] [email protected] [ 115.00-600.00] 372.9 100 80 577->433-> 60 m/z 115-600 40 20 Rel ati ve Abundance 354.6 404.5 432.8 337.1 373.9 448.5 460.2 485.6 529.7 565.0 0 150 200 250 300 350 400 450 500 550 600 m/z OLEANDER: Often mistaken for eucalyptus (gum) tree leaves Oleander Eucalyptus Oleander – Toxicity & Clinical Signs • Animals, humans and birds susceptible • All parts (dried and fresh) are toxic • Minimum lethal doses: ~ 5 leaves (horses, cattle) • Cattle: 18 g of oleander leaves per adult cow • Horses: 20 – 30 g of oleander leaves per adult horse • Sheep: 1 – 4 g of oleander leaves per adult sheep • Clinical signs: within a few hours of exposure • Diarrhea, depression, anorexia, excess salivation • Cardiac signs: bradycardia, tachycardia, arrhythmias • Sudden deaths • Kidney failure Oleander Exposure Horse Cow Left ventricular free wall: Hemorrhagic degenerative foci Cow Oleander – Gross lesions in Camelids Grasses that cause Trauma • Exposure to sharp grass awns and barbed bristles or prickly plant parts à injury to lips, oral cavity, tongue, and gingiva • Clinical sign in horses and cattle: • Loss of appetite, drooling • Oral ulcers, granulation tissue • Why worry? • Clinical signs very similar to highly contagious viral diseases such as vesicular stomatitis and foot-and-mouth disease • Treatment: • Remove foreign body/plant material (may have migrated) • General care for abscesses and infections Setaria glauca (yellow foxtail) Setaria spp. – Bristlegrass other names: yellow foxtail, bristly foxtail, green foxtail, purple foxtail ALFALFA HAY Yellow bristlegrass.