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ICC: Farm Animal > FAC27: Farm Animal Toxicology (Plant Poisons) > Flashcards

FAC27: Farm Animal Toxicology (Plant Poisons) Flashcards

1
Q

What are the common causes of plant toxicity cases?

A
  • Poor pasture availablity
  • Overgrazing/poor pasture management
  • Forage conservation
  • Accessibility to poisonous plants
  • Grazing experience
  • Transportation
  • Environmental factors
  • Species suceptibility
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2
Q

What are the different types of plant toxins?

A

Alkaloids

Glycosides

  • Cyanogenic glycosides
  • Goitrogenic glycosides (glucosinolates)
  • Cardiac glycosides
  • Saponins

Nitrates/Nitrites

Oxalates

  • Photosensitising agents
  • Primary
  • Hepatogenous

Proteins, peptides, and amino acids

Tanins

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3
Q

How do alkaloids cause toxicity?

A

They are structurally similar to ACh, dopamine, and serotonin > mimic or block the action of neurotransmitters

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4
Q

How do cyanogenic glycosides cause toxicity?

A

Cyanogenic plants contain an enzyme system capable of converting glycosides to hydrocyanic acid > inactivates the cytochrome oxidase system in mitochondria > starves cells of oxygen

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5
Q

How do goitrogenic glycosides cause toxicity?

A

Glucosinolates interfere with thyroid hormone synthesis. Thiocyanates impair uptake of iodine by the thyroid gland.

They cause goitre, reduced growth rates, and/or diarrhoea

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6
Q

How do cardiac glycosides cause toxicity?

A

They have a specific action on the myocardium, increasing contractility and slowing the heart rate > heart problems.

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7
Q

How do saponins cause toxicity?

A

absorbed very slowly but can cause gastroenteritis

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8
Q

How do nitrates/nitrites cause toxicity?

A

Nitrites are formed in the rumen after ingestion of nitrate from soil

Absorbed nitrites combine with haemoglobin in the blood to form methaemoglobin, which is incapable of transporting oxygen > anoxia

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9
Q

How do you differentiation HCN poisoning from nitrite poising?

A

Nitrate: blood is dark brown in colour

HCN: bright red

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10
Q

How do oxalates cause toxicity?

A

Rumen absorbes free oxalate and precipitates calcium oxalate crystals in submucosal arteries > damages lung capillaries and causes pulmonary oedema, nephrosis (due to crystals), hypocalcaemia

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11
Q

How does photosensitisation cause toxicity?

A

Accumulation of photosensitive metabolites under the skin and their reaction with sunlight to cause necrotic damage

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12
Q

How does primary photosensitisation cause toxicity?

A

Movement from poor to lush green pasture and fail to adapt to increased amounts of chlorophyll

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13
Q

How does secondary photosensitisation cause toxicity?

A

Biliary excretion of phylloerythrin (a normal degradation product of chlorophyll that is normally excreted in bile) is obstructed due to various liver diseases

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14
Q

How do the amino acids in Brasscia crops cause toxicity?

A

The amino acid S-methyl cysteine sulfoxide (SMCO) is converted in the rumen during normal fermentation to dimethyl disulphide. This metabolite causes poor growth rates and haemolytic anaemia.

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15
Q

How do tanins cause toxicity?

A

Hydrolysable tannins are broken down to toxic metabolites in the digestive tract of cattle and sheep

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16
Q

How do you treat cyanogenic glycoside toxicity?

A

IV sodium thiosulphate and sodium nitrite

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17
Q

How do you treat goitrogenic glycoside toxicity?

A

Glucosinolate induced goitre cannot be managed by iodine supplementation, while thiocyanate induced goitres can

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18
Q

How do you treat cardiac glycoside toxicity?

A

Supportive fluid therapy, atropine, and propranolol

Oral administration of charcoal and rumenotomy have been effective

19
Q

How do you treat nitrite toxicity?

A

IV infusion of methylene blue

20
Q

How do you treat oxalate toxicity?

A

Short term: calcium borogluconate therapy

But most relapse and die

21
Q

How do you treat photosensitising agent toxicity?

A

Remove from sun

22
Q

How do you treat tanin toxicity?

A

Liquid paraffin with milk, mucilage, and appetite stimulants

Saline purgatives are contra-indicated because of kidney damage

23
Q

What plants contain alkaloids?

A

Yew, Laburnum, Ragwort, Hemlock, Lupin,

24
Q

What plants contain cyanogenic glycosides?

A

Linssed and Cherry Laurel

25
Q

What plants contain goitrogenic glycosides?

A

Brasscia crops and white clover

26
Q

What plants contain cardiac glycosides?

A

Foxglove, Lilly of the Valley, Oleander

27
Q

What plants contain saponins?

A

Common Ivy

28
Q

What plants contain nitrates?

A

Nitrates are absorbed from the soil

Clovers and Brassica accumulate high concentrations

29
Q

What plants contain oxalates?

A

Sugar beet, rhubarb, sorrel

30
Q

What is the comparative level of susceptibility for sheet, horses, cattle?

A

Sheep> horses> cattle

31
Q

What plants contain photosensitising agents?

A

Primary: St. Johns wort, Buckwheat

Hepatogenous: Bog Ashopedl, Ragwort

32
Q

What plants contain proteins, peptides, and amino acids that cause toxicity?

A

Aminotoxins: toxic mushrooms

Hepatotoxic peptides: blue-green algae

S. methylcystein sulfoxide: brassica crops

Thiaminase: horsetail and bracken

33
Q

What plants contain tannins?

A

oak tree, unripe acorns

34
Q

Which is more toxic: young or old bracken?

A

younger plants are most toxic

35
Q

What toxins are found in bracken?

A

Thiaminase, ptaquiloside, aplastic anaemia factor, prunasin

36
Q

What toxin is found in rhododendron?

A

Andromedotoxin that causes hypotension, respiratory depression, CNS excitation and then depression

37
Q

What toxin is found in ragwort?

A

Pyrrolizidine that is metabolised into reactive pyrrols, which has a toxic effect on the liver

38
Q

Which is more toxic: flowering or non-flowering ragwort?

A

Flowering plants are most toxic

39
Q

What is the toxin in yew?

A

Taxine which strongly depresses the heart and causes sudden death

40
Q

What is the toxin in laburnum?

A

Cystine: stimulation of respiratory center, excitation of skeletal muscles, paralysis of peripheral sympathetic nerve ganglion

41
Q

When is rape most toxic?

A

When it is in flower

42
Q

What toxin is in rape?

A

Goitrogenic glucoside, nitrates, S methyl cysteine sulfoxide

43
Q

What toxins are in the carrot family?

A

Alkaloid and furocoumarins (photosensitising agent)

ICC: Farm Animal (54 decks)

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