Lecture 29 - Selenium, Fescue

Selenium poisoning presents as lots of diseases depending on the__, __,__, and ___.

form of selenium, duration, route of exposure, animal species

True or False? Selenium poisoning only occurs acutely.

False. Selenium poisoning can be BOTH acute and chronic.

What general systems are targeted with acute selenium poisoning?

lung, heart, liver, kidney, less commonly skeletal muscle, nervous (swine only)

What disease is caused by chronic selenium poisoning?

“bobtailed” disease

If you see this, think ____! (not pathognomic)

selenium poisoning

What are sources of selenium poisoning?

• high selenium forages (location driven) areas in WA, ID, MT

• selenium supplements (mix, math errors, wrong supplement)

• water contamination

Selenium content varies in ___ plants and categorized into ___ and ____.

accumulator,

obligate, facultative

True or False? Obligate accumulator plants accumulate higher amounts of selenium and tends to be more palatable than facultative plants.

False. Obligate plants tends to be LESS palatable, facultative plants passively accumulate selenium and tend to be more palatable.

What species are susceptible to selenium poisoning?

All species, horses most sensitive and primarily LA production animal problem

Clinical signs and lesions will vary between ___ and __ of exposure - it is a ____ problem.

species, duration

multisystemic

What clinical signs and lesions are seen with acute selenium poisoning?

cardiac, lung (liver, kidney, skeletal muscle), neurologic - poliomyelomalacia in swine

What clinical signs and lesions are seen with chronic selenium poisoning?

lame, rough hair coat, hair loss (mane and tail), anorexia, hoof deformities - circular breaks below coronary band

How do you diagnose selenium toxicity?

• history of exposure - find the source

• clinical signs and lesions vary between species, dose, form, duration (heart, lung, liver, kidney, neuro in swine)

• analytically

  • antemortem: whole blood

  • postmortem: liver, kidney

  • source (water, feed)

  • chronic: hair and hoof

What is the treatment for selenium poisoning?

symptomatic and supportive - supplement with S, Mn, Zn if chronic

What is Se deficiency?

aka white muscle disease (cows, goats, sheep, horses) affecting heart, and skeletal muscle in horses causing masseter muscle myopathy

___mining in the Western ___ Formation resulted in what?

Phosphorous, Phosphoria

high selenium

Fescue poisoning is caused by animals eating _____ which contains ____ which is a ____.

tall fescue,

endophyte, mycotoxin

Fescue poisoning is a ___ problem all throughout US and most fesuce is infected. Any feed where infection rate ___% can be problematic.

common,

>5%

What is the toxin in fescue poisoning?

loline and ergot alkaloids - ergovaline

What is the alkaloid that is tested for fescue?

ergovaline

What is the major mechanism of action of fescue toxicity?

alpha adrenergic receptors → peripheral and other vasoconstriction

D2 dopamine receptors → suppression of prolactin secretion

What are the 3 major clinical diseases from fescue poisoning?

summer slump, fescue foot, reproductive problems

Describe the clinical disease seen in summer with fescue poisoning

summer slump - cattle, vasoconstriction

hyperthermia, decreased feed intake, loss of body weight, poor coat, abortions

Describe the clinical disease seen in winter with fescue poisoning

fescue foot - cattle, vasoconstriction

ischemic necrosis (dry gangrene) of distal extremities, loss of appetite, lameness, inflamed fetlocks, loss of tips of ears and tail, abortions

Describe the clinical disease seen all year with fescue poisoning

reproductive problems - horses, cattle, sheep

prolonged gestation, thickened placentas, dystocias, large weak young (dysmature), agalactia, abortions

How do you diagnose fescue poisoning?

• three diseases - abortions seen in all 3

• ingesting tall fescue - endophyte

• test hay for ergovaline // urine testing not common

What is the treatment for fescue poisoning?

symptomatic and supportive,

Domperidone (repro + agalactia).- dopamine antagonist for horses; changes will last as long as horse on fescue; stop exposures last 1-3 months of gestation

prevention is key - may not be cost effective to treat

True or False? Animals with fescue poisoning cannot go to market due to residues.

False. Animals with fescue poisoning have no significant residue issues.