Why You Should Worry

Transcription

1 Poisonous Weeds And Toxic Factors In Hay Crops: Why You Should Worry Birgit Puschner Veterinary Toxicologist School of Veterinary Medicine, UC Davis

2 Overview of Today s Talk When to suspect a poisoning Toxic plants: Nitrate accumulators Pyrrolizidine alkaloids Oleander Grasses that cause mechanical irritation

3 Factors Contributing to Poisoning Animal Sensitive species Adaptation to tolerate toxic plants is possible What other feed is available? Unable to avoid toxic plant (i.e. in hay cubes) Plant Palatable? Right time of the year? à concentrations of toxins vary with season Does the plant remain toxic when dried?

4 Resources Textbooks: A Guide to Plant Poisoning of Animals in North America: by A.P. Knight and R.G. Walter, 1st edition, Teton NewMedia. UCANR publication: Detailed publication on Livestock-poisoning Plants of California (link on CERE under Lab resources) Websites (with images and location)

5 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

6 Orchard Grass Hay 5,900 ppm Nitrate Pigweed

7 Sudan Hay 18,800 ppm Nitrate

8 Amaranthus retroflexus

9 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

10 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)

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13 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

14 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

15 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

16 Interpreting Nitrate Forage Tests (differing reporting units) NO3 (dry matter) NO3-N (dry matter) KNO3 (dry matter) Feeding Recommendations < 5,000 ppm (0.5%) < 1,200 ppm (0.12%) < 8,100 ppm (0.81%) Generally Considered Safe for Livestock > 5,000 ppm (0.5%) but < 10,000 ppm (1%) ppm > 1,200 ppm (0.12 %) but < 2,300 ppm (0.23%) > 8,100 ppm (0.81%) but < 16,000 ppm (1.62%) Caution: Problems can occur at this level >10,000ppm (1%) > 2,300 ppm >16,200ppm (1.62%) Do not feed

17 Pyrrolizidine Alkaloid Containing Plants Common groundsel Senecio vulgaris

18 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

19 Common Groundsel Senecio vulgaris

20 Senecio vulgaris Common Groundsel

21 S. vulgaris in alfalfa hay (white seed heads, fluffy)

22 ALFALFA HAY Sowthistle (look alike, Common groundsel (toxic)

23 PA-contaminated Alfalfa Pellets

24 Fiddlenecks Amsinckia spp.

25 Tansy Ragwort Senecio jacobaea

26 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

27 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

28 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

29 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

30 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

31 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)

32 Hay fed to cows

33 Diagnosis Oleander Poisoning Identification of leaves in ingesta Chemical analysis of serum, urine, ingesta RT: SM: 15G RT: 5.58 MA: Oleandrin RT: 5.6 min NL: 7.50E4 m/z= F: + c ESI Full ms @ @18.00 [ ] MS Relative Abundance Time (min) # RT: AV: 23 SB: , NL: 4.69E4 F: + c ESI Full ms @ @18.00 [ ] Relative Abundance >433-> m/z m/z 565.0

34 OLEANDER: Often mistaken for eucalyptus (gum) tree leaves Oleander Eucalyptus

35 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: 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

36 Oleander Exposure Horse Cow Left ventricular free wall: Hemorrhagic degenerative foci Cow

37 Oleander Gross lesions in Camelids

38 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

39 Setaria glauca (yellow foxtail)

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42 Setaria spp. Bristlegrass other names: yellow foxtail, bristly foxtail, green foxtail, purple foxtail ALFALFA HAY Yellow bristlegrass