week 2: toxic plants

What are the qualities of a good pasture?

• Highly palatable
• High nutrient value
• Withstand climate extremes
• Good moisture content
• High leaf-to-stem ratio
• Fast regeneration

What are the situations that lead to toxic plant poisoning?

• Animals moved to new pasture when hungry
• Pasture sparse due to overgrazing
• Poor growth in spring, or drought conditions
• Herbicide application to control weeds
• Recent nitrogen fertilizer application
• New forage source (hay, silage)

Besides feed additives, what is the most common source of toxicosis in large animals?

toxins in pasture plants

What is the toxin principle?

How can toxin concentrations vary?

• Plant
• Type
• Wild – weeds, forage
• Landscape cultivars
• Part
• Root
• Stem
• Leaf
• Fruit/Seed
• Growing season
• Time of year
• Conditions – wet, drought
• Location
• Region of US
• Section of pasture

What is the key characteristic to identifying pigweed?

Large seed head – late summer, fall

What are the clinical signs of pigweed poisoning? What species are most commonly affected?

-Perirenal edema - pigs, some cattle
• Straw colored fluid in/around kidneys
• Ascites/hydrothorax/Edema
-Renal toxicity – necrosis, increased BUN, Creat
-Coma/death 2-15 days

What parts of the rhubarb plant are safe/toxic?

-Safe: stem

-Toxic: leaves (oxalic acid concentration)

What happens physiologically to an animal that ingests rhubarb?

• GI: mouth/stomach irritation, abdominal pain, vomiting,
• Musculoskeletal: tremors, weakness
• Hypocalcemia – oxalates bond to blood calcium
• Renal: PU/PD, blood in urine
• Calcium Oxalate precipitates in renal tubules – nephrosis
• Acute renal failure

What issues arise from ingestion of oak leaves? How can this issue be avoided?

• Initial GI signs
• Loss of appetite, black feces, diarrhea with blood
• Weak, rapid pulse
• Lethal kidney toxicity
• Gallotannins convert to tannic acid and gallic acid
• Frequent urination
Treatment
• Supportive care
• IV fluids
• Laxatives
• Surgery
• Rumenotomy/gastric lavage
• Prevent by feeding quality forage

What species is affected by red maple toxicosis?

horses

What is the key to identifying red maple from other maple species?

red stem

What happens when wilted choke cherry tree leaves are ingested by ruminants?

Rapid progression – excitement, tremors, convulsions, death (minutes)

What are key characteristics of the Ohio buckeye/horse chestnut tree? What parts are toxic?

• Palmate five leaflets
• Yellow flowers at end of branch
• Prickly fruit with glossy brown seed

Toxic part: Buds, nuts, leaves, bark, seedlings

What makes sorghum species/millet toxic?

toxic levels of cyanide and nitrates

What is photosensitization? What plant causes this reaction?

-animal becomes sensitive to sunlight

-caused by phototoxins and hepatotoxins

What should be done with an animal exhibiting photosensitivity?

Sensitize the skin through contact or ingestion

What are key characteristics to identify water hemlock?

• CNS – stimulant, fits, convulsions
• Hypothermia secondary
• Respiratory paralysis
• Rapid progression to coma, death (2 hrs)

How toxic is water hemlock to horses?

eating 8 ounces is lethal

What are nicotinic receptor clinical signs?

-rapid onset

-bradycardia

What are the key characteristics to identify yew?

• Dark evergreen shrub
• Flat needle leaves
• Red cupped berry

What is the key to identifying poison hemlock?

• Very tall!
• In carrot family – looks, smell
• Broad flowering head with many clusters of small white flowers
• Purple blotches on stem definitive ID

What plant is poison hemlock often confused with?

How toxic is poison hemlock to horses?

consuming 4-5 lbs is lethal

“Red as a beet, dry as a bone, blind as a bat, mad as a hatter,” refers to the clinical signs of what toxic plant? What causes these signs? Explain.

Jimsonweed

• Hyoscyamine, hyoscine, atropine – high doses

What plant is hallucinogenic at high doses?

jimsonweed

What is the key characteristic to identify jimsonweed?

• Spikey leaves
• Spikey seed pod

What toxic plant has tiny tomato-like fruit that is non-toxic when mature, but toxic when green?

nightshade

What are the clinical signs of nightshade poisoning?

• NS – weakness, coma, resp paralysis, death
• Disruption of parasympathetic NS to regulate
involuntary activity

What is milk fever?

cumulative, excreted via lactation

How is white snakeroot excreted?

via lactation

What are clinical signs of white snakeroot ingestion in horses? Other species?

• Horse: partial throat paralysis, CHF

• Muscle trembling, progressive weakness, death
• Acetone breath - ketosis
• Nursing young affected

What are mycotoxins?

Produced by fungi infecting the plant, not the plant itself

The fungus that grows on moldy sweet clover produces what condition physiologically?

-Clover is damaged and becomes moldy

-circulatory system: petechia, bleeding

What is black patch disease?

Characteristic brown spots

What are the clinical signs and treatment of black patch disease?

• Clinical Signs
• “Slobbers” in horses
• Abortion and infertility
• Treatment
• Remove infected hay

What is ergot, and where do you find it?

Ergot (fungus) grows on Fescue (grass) seed

What conditions in cattle are caused by ergot?

• Fescue foot
• Fat Necrosis
• Abortion/Dystocia

What is thiaminase, and what happens when it is ingested?

-Ptaquiloside

• Horses: CNS – incoordination, seizures
• All species: Bone marrow aplasia

What species is affected by the black walnut tree? What are the clinical signs? How is it treated?

-horses

• Clinical Signs
• Horses – Laminitis
• Within 12-24 hours after contact
• Treatment
• Remove bedding!
• Supportive care
• IV fluids
• Pain mgmt – NSAIDS/Analgesics

What are cyanobacteria, and what do they create?

Blue-Green Algae

• Blue-green or red-brown
• Mats, foam, or scum on water

What plant causes mechanical irritation to the GI tract when its seed pods are ingested?

cocklebur

What is the toxin found in marijuana? What clinical signs are seen with marijuana ingestion?

• Toxin
• THC (delta-9-tetrahydrocannabinol)
• Found in all parts of the plant
• Clinical Signs
• Sedation
• Ataxia, stupor, light euphoria

How should pastures be managed to avoid toxicities?

Grazing management key to minimize risk & maximize forage
• Implement strategies to minimize weed spread (mowing, over seeding,
herbicide)
• Evaluate/Reevaluate effectiveness of management plan
• Change methods or timing if necessary
• Vary techniques to minimize costs