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Selenium toxicosis Flashcards

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1
Q

T/F: Overdosing selenium deficiency treatment can lead to selenium toxicosis

A

TRUE

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2
Q

What levels are considered selenium deficient?

A

<0.05 ppm

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3
Q

Selenium deficiency diseases?

A
  • White muscle disease (WMD) or nutritional muscle dystrophy (NMD) in lambs, but also seen in calves and foals
  • Hepatosis dietetica in young pigs
  • Exudative diathesis in chicks
  • Nutritional pancreatic atrophy in chickens
  • Porcine stress syndrome in pigs
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4
Q

Where is selenium deficient soil common?

A
  • Northwest
  • Northeast
  • Southeast
  • Great lakes
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5
Q

What level of selenium qualifies soil as selenium-rich? Where is it located?

A
  • 2-10 ppm
  • South Dakota
  • North Dakota
  • Wyoming
  • Montana
  • Nebraska
  • Kansas
  • Utah
  • Colorado
  • New Mexico
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6
Q

What are the selenium requirements?

A

0.1 mg/kg (depends on vitamin E)

Remember: 0.1mg/kg = 0.1ppm

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7
Q

What are the various uses for selenium?

A
  • Feed supplements for cattle, sheep, swine, and poultry
  • Injectable selenium-vitamin E preparations
  • Antioxidant supplements (animal and human)
  • Used in medical shampoos for treatment of dermatitis
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8
Q

Sources of selenium?

A
  • Cattle, sheep, and horses may graze seleniferous plants
  • Swine and poultry may eat grains grown on selenium-rich soil
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9
Q

What are seleniferous plants? What are the various types?

A

Plants that accumulate Se in Se-rich soil

Obligate accumulators (Se-indicator plants), facultative accumulators, and passive accumulators

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10
Q

How much Se can obligate accumulators accumulate?

A

Up to 15,000 ppm Se

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11
Q

T/F: Obligate Se accumulators require Se for growth

A

TRUE

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12
Q

What plants are obligate accumulators of Se?

A
  • Astragalus (locoweed, milk vetch)
  • Stanleya (prince’s plume)
  • Oonopsis (golden wood)
  • Xylorrhiza (woody aster)
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13
Q

How much Se can facultative accumulators collect?

A

Accumulate up to 25-100 ppm

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14
Q

Do facultative accumulators require Se?

A

Nope, but they can accumulate it

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15
Q

Examples of facultative accumulators?

A
  • Aster
  • Atriplex (saltbush)
  • Castilleja (paint brush)
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16
Q

Passive accumulators: Se levels?

A

Accumulate up to 1-25 ppm Se

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17
Q

Where do passive accumulators build up Se?

A

Accumulate Se passively in Se-rich soil

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18
Q

Examples of passive Se accumulators?

A

Many plants including crop plants such as corn, wheat, oats, barley, grass, hay, and other plants

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19
Q

Causes of Se toxicosis?

A
  • Overdosage w/ Se preparations or supplements
  • Se-contaminate water causes teratogenic effects in waterfowl
  • Improper use of Se-medicated shampoos may cause toxicosis in small animals
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20
Q

What is this?

A

Astragalus (locoweed)

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21
Q

What is this?

A

Astragalus (milkvetch)

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22
Q

What is this?

A

Stanleya pinnata (prince’s plume)

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23
Q

T/F: Se is a non-essential trace element

A

FALSE–it is an essential trace element

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24
Q

What 3 states does Se have?

A

3 oxidation states: selenate (+6), selenite (+4), and selenide (+2)

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25
What elements are Se's physical and chemical properties similar to?
Sulfur and arsenic
26
T/F: Se combines with the -NH3 group of glutathione
FALSE--Se combines with the -SH group of glutathione
27
What is Se a component of?
Glutathione peroxidase (GSH-Px)
28
How does selenium act as an antioxidant?
By prevention of peroxide accumulation through reduction of glutathione
29
What is synergistic to GSH-Px?
Vitamin E
30
What does Se-vitamin E prevent?
Cellular degeneration and cell membrane damage in animals and poultry
31
T/F: Se is also found in 5-deiodinase (conversion of T4 to T3)
TRUE
32
What is Se an irritant to?
Mucous membranes (like other metals)
33
What is the toxicity of the various Se forms (greatest to least)?
Organic Se in plants \> selenate = selenite \> selenide \> synthetic organoselenium compounds
34
What are the acute toxic doses of oral selenium (selenite)?
* 3.3 mg/kg in the horse * 10 mg/kg in cattle * 17 mg/kg in swine
35
What is the oral Se subacute toxic level for swine?
20-50 ppm for 3 days or more
36
What is the chronic toxic level of selenium?
5-10 ppm for several weeks or months in horses, cattle, and swine
37
Which soil promotes formation of selenate?
Arid alkaline soil of the Great Plains
38
T/F: Elemental Se is relatively nontoxic
TRUE
39
What is toxicity reduced by?
High protein diet and ingestion of other elements that bind Se such as Cu
40
T/F: Seleniferous plants are odorless and palatable
FALSE--Seleniferous plants have a **bad odor** and are **unpalatable** (only eaten when other forage is unavailable)
41
Where is Se readily absorbed from?
Small intestine
42
Which Se state is more readily absorbed?
The soluble organic Se in plants is more rapidly absorbed than selenite, selenate, and selenide
43
Is elemental Se absorbed?
Nope--it's not soluble in water
44
Where is Se distributed in the body?
Distributed throughout the body particularly to the liver, kidney, and spleen
45
Chronic exposure of Se leads to high concentrations where in the body?
Hair and hoof
46
T/F: Se crosses the placenta (teratogenic) but is not excreted in milk
FALSE--it crosses the placenta **and** **is** excreted in milk
47
Where is Se excreted? What increases its excretion?
Se is mainly excreted in urine, but also in bile Arsenic increases **biliary** excretion
48
T/F: Se causes irritation of GI mucosa (subacute and acute)
TRUE
49
Se toxicosis causes dramatic depletion of what?
Tissue glutathione (GSH)
50
What does Se replace following Se toxicosis?
Replaces sulfur in amino acids causing abnormal proteins
51
What does Se toxicosis decrease?
Decreases ATP in chronic toxicosis Decreased tissue absorbic acid
52
What is death in acute and subacute Se toxicosis mainly due to?
Respiratory insufficiency resulting from pulmonary edema and hemorrhage
53
What might death in chronic Se toxicosis be due to?
Starvation and thirst resulting from weakness, lameness, blindness
54
Clinical signs of acute oral Se toxicosis?
* Onset in a few hours to a few days * GI signs such as colic, bloat, and dark watery diarrhea * Resp signs such as labored resp w/ fluid sounds in the lungs, bloody froth from the nares, and cyanosis * Other signs include fever, polyuria, mydriasis, and uncertain gait * Death in hours
55
Clinical signs of acute parenteral Se toxicosis?
Neuro signs including mydriasis and incoordination
56
What do ranchers call subacute Se toxicosis in cattle?
"Blind staggers"
57
Clinical signs during stage 1 of subacute Se toxicosis in cattle?
* Poor appetite * Aimless wandering * Circling * Walking through objects * **Normal respiration and temperature**
58
Clinical signs during stage 2 of subacute Se toxicosis in cattle?
* Stage 1 signs +: * Depression * Incoordination * Foreleg weakness and walking on the knees * Complete anorexia
59
Clinical signs during stage 3 of subacute Se toxicosis in cattle?
* Colic * Hypothermia * Emaciation * Clouded corneas near blindness * Paresis * Coma * Death in a few hours
60
Clinical signs of subacute Se toxicosis in sheep?
Signs are similar to cattle but the stages are not well defined
61
Clinical signs of subacute Se toxicosis in swine?
* A neuroparalytic condition called "porcine focal symmetrical poliomyelomalacia" * Neuro signs include coordination, lameness, and paralysis * Other signs including alopecia, hoof abnormalities and separation of the hoof
62
Clinical signs of chronic toxicosis (alkali disease)?
* Rough hair coat, loss of hair from mane and tail * Hoof deformities and sloughing, stiffness of joints, and lameness * Partial blindness, anemia, lethargy, emaciation, infertility, and birth defects
63
What are the lesions of acute Se toxicosis?
* Hemorrhagic gastroenteritis * Congestion of organs * Hemorrhages * Pulmonary edema * Hydrothorax * Gut contents may smell like rotten garlic or rotten horseradish (hydrogen selenide)
64
What are the lesions of subacute Se toxicosis in swine?
Focal symmetrical poliomyelomalacia
65
What are the lesions of chronic Se toxicosis?
* Abnormal hooves * Cardiac damage * Hepatic necrosis
66
Lab analysis of Se toxicosis (acute vs. chronic)?
* Elevated Se (\> 2ppm in acute and \>5ppm in chronic) * Acute: blood, kidney, liver * Chronic: hair and hoof (must be **washed** before analysis) * Blood or plasma glutathione peroxidase activity correlates well w/ blood Se concentration in cattle, sheep, and swine (but NOT in horses)
67
DDx for acute or subacute Se toxicosis?
* Pneumonia * Infectious hepatitis * Enterotoxemia * Pasteurellosis
68
DDx for chronic Se toxicosis?
* Molybdenum toxicosis * Flouride toxicosis * Freezing * Ergotism * Laminitis
69
What is the treatment for acute Se toxicosis?
* Saline cathartics * Symptomatic therapy (oxygen, treatment for pulmonary edema, circulatory shock, and gastroenteritis) * Acetylcysteine (140mg/kg IV, followed by 70mg/kg daily in 4 divided doses)
70
What are some preventions for subacute and chronic Se toxicosis?
* Soil and forage should be tested regularly for Se levels * Remove the animals from seleniferous areas * Addition of Cu to the diet, high protein diet, increasing Su-containing proteins may reduce toxicosis * Addition of organic arsenicals to the diet increases biliary excretion of Se
71
Prognosis of acute Se toxicosis?
Poor--animals die quickly

Toxicology (22 decks)

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