Toxicology Lecture 21A Zearalenone, Phytoestrogens, Clover

Front 1

What naturally produces Zearalenone?

Back 1

The fungus Fusarium roseum and by some isolates of Fusarium moniliforme

Front 2

What are 3 common substrates zearalenone is found in?

Back 2

Corn, wheat, barley, occasionally oats

Front 3

What conditions favor zearalenone production?

Back 3

High humidity and cooler temperatures in both field & storage

Front 4

What type of plants tend to contain phytoestrogens that can effect the reproductive system (infertility)?

Back 4

Many legumes

Front 5

What are 4 legumes that contain phytoestrogens that can cause infertility?

Back 5

1) White clover
2) Subterranean clover
3) Red clover
4) Alfalfa

Front 6

**What are the polyphenolic compounds that are among the most active in estrogenic effects?

Back 6

Coumestans
Isoflavones

Front 7

What is the mechanism of action of phytoestrogens?

Back 7

Extensively metabolized in rumen and rapidly absorbed--> phytoestrogens then bind w/ high affinity to estrogen receptors and display estradiol-like effects

Front 8

What are the 2 legumes that contain phytoestrogens that tend to affect cattle most often?

Back 8

Red clover and alfalfa

Front 9

What is the primary effect of phytoestrogens from red clover and alfalfa in cattle?

Back 9

Infertility

Front 10

What is clover disease?

Back 10

Phytoestrogen toxicity in sheep resulting in INFERTILITY

Front 11

What are 2 methods to diagnose phytoestrogens?

Back 11

1) Measurement of phytoestrogen levels in forage material
2) Testing for elevated levels of circulating estrogen

Front 12

What is the prognosis of phytoestrogens?

Back 12

Animals rarely die but may have permanent infertility

Front 13

When does red clover become toxic (what time of the year)?

Back 13

Pasture forages containing clover in low-lying fields can become toxic during extended wet conditions followed by hot, sunny days in spring and summer

Front 14

What is the mode of action of red clover toxicity?

Back 14

(?) toxins are probably fungal in origin. Trifoium pratense- when attacked by Rhizoctonia leguminicola, the muscarinic toxin, slaframine is often present at toxic concentrations

Front 15

What are the clinical signs of red clover toxicity in cattle & horses?

Back 15

Photosensitization, the white skin typically becomes red & swollen, it may slough leaving unsightly scares
-skin of muzzle and teats especially vulnerable

Front 16

What are 2 components of treating red clover toxicity?

Back 16

1) Withdrawl from source
2) Animals suffering from photosensitization need shade and water

Front 17

What is the prognosis of red clover toxicity?

Back 17

animals rarely die

Front 18

What is the source of alsike clover?

Back 18

Perennial legumes commonly grown in pasture or hay and may be found as escapes in fields, roadsides and waste areas

Front 19

What is the mode of action of alsike clover toxicity?

Back 19

Contains an unknown agent that causes primary and/or secondary (hepatogenous) photosensitization

Front 20

Light-skinned animals are particularly affected when allowed to graze on alsike when it is ___________.

Back 20

Dew-covered or wet

Front 21

What animals are affected by alsike clover?

Back 21

Most often in horses, but all grazing animals may be affected

Front 22

*What is a sign specific in animals poisoned following ingestion of dew-dampened alsike clover?

Back 22

Refuse to eat

Front 23

What are some clinical signs of alsike clover toxicity (not long term)?

Back 23

May drool, tongues and lips become swollen
-photosensitization (sloughing)

Front 24

What are some clinical signs of alsike clover toxicity in sheep?

Back 24

Eyelids, ears, nose and mouth swell, giving rise to the name big head-at first ooze serum then later scabs may form
-intense itching may develop

Front 25

The long-term consequence of alsike clover consumption is "___________ syndrome".

Back 25

Big liver syndrome

Front 26

What is big liver syndrome?

Back 26

Long term consequence of alsike clover consumption, appears as a progressive destruction of the liver w/ increased connective tissue (appears as an enlarged liver)

Front 27

What is the toxic dose of alsike clover?

Back 27

Should not be fed to horses in greater than 5% of the feed

Front 28

How do you diagnose alsike clover toxicity?

Back 28

Liver biopsy may be required to characterize the degree and type of liver damage and provide a prognosis

Front 29

What is the treatment for horses with photosensitivity due to alsike clover consumption as the primary clinical finding?

Back 29

May recover after being moved to Alsike-free pasture

Front 30

What should you do for animals that have severe sunscald from alsike clover consumption?

Back 30

Keep out of sun until recovered (turn them out at night)

Front 31

What is the treatment with animals that have severe stomatitis or dermatitis due to alsike clover consumption?

Back 31

Supportive care
Local treatment of stomatitis until heals

Front 32

What are 3 ways to prevent alsike clover toxicity?

Back 32

1) Remove animals from pastures especially early in morning when plants are dew-covered
2) Seed mixes intended for horse pastures and hay should not contain alsike clover
3) Horse owners should be able to recognize the different clovers so that alsike clover poisoning can be prevented