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7/31/2019 Plant Toxicity, Toxic Compounds, And Signs
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Plant Toxicity, Toxic Compounds, Signs
Tannins
Polyphenolsinclude tannins(assist in tanning hides)
Condensed tannins are large and present in many plant tissues
Condensed tannins may prevent prowling by animals
May inhibit microbial activity and confer disease resistance
Found in leaf of tea, trefoil and sainfoin, flower petal of trefoil,
sainfoin, white and red clovers; seed coat of most legumes
Presence is due to a single gene
Trefoil tannins vary in spring, decrease towards autumn in soil low
in Sulphur or Phosphorus or in presence of grass
Tannin EffectsHigh tannin forages have low digestibility
Tannins inhibit microbes and enzymes in gut, bind proteins,
chelate metal ions
May sometimes aid protein utilization
Low tannin forage varieties exist
Phytoestrogens (low activity)
Includes: coumestans, isoflavones, isoflavans
Mainly from alfalfa and white clover
Low in healthy plants, elevated in disease
Coumestans associated with fungal mycelium and spores
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Cyanogenic Glycosides
Nitrogenous compounds in white clover, sorghum (contain C, N,
sugar)
Plants release cyanide (HCN) when tissue disrupted, mainly in cool
spring or distress
May have evolved to protect young plants from being grazed by
insects or mammals (herbivory)
May predispose animals to Se deficiency
Cyanide toxicity- uncoupling mitochondrial oxidative
phosphorylation and inhibiting cellular respiration
Alkaloids
Alkaline nitrogenous compounds, with pharmacological activity
Four different forage situations:
Indole Alkaloids
Phalarisincludes Reed Canarygrass, which has wild varieties
high in alkaloids and modern low alkaloid varieties
Effects include low intake of grass, diarrhea, neurologicaldisorder, cardiac failure
Indole concentration can rise, high soil nitrogen, high
temperature, shading, moisture stress
Unsaturated Pyrrolizidine and Ergopeptide Alkaloids
Alkaloids may be produced by plant cells or fungal parasites
of those plants
Some are insecticidal at low doses
Perennial ryegrassmay produce tremors
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Endophy-infected grassesmay tolerate drought better and
extract soil phosphorus more efficiently
Ergot Alkaloids
Ergot is infection by Clavicepsfungus in seed heads of
grasses and grains, visible as hard dark masses, larger than
seeds
Ergotoxine stimulates nerves that constrict small blood
vessels, causing gangrene in extremities, abortions,
nervousness, deathThe alkaloid is related to lysergic acid
Quinolizidine alkaloids in lupines
Lupines are flowering plants which contain quinolizidine
alkaloids
Of 200 lupine species, only 3 or 4 are used much for forage
and 10-20 are used for seed production
QUinolizidine alkaloids contain 2, 3, or 4 rings made of C and
N
High ammonium nitrate fertilizer promotes formation of these
alkaloids
K deficiency or imbalance of other minerals may increase
alkaloid content
High alkaloid lupine lines are bitter
Low alkaloid lines are called sweet lupines
Lupine effects on cattle:
Crooked calf, cleft palate, distorted spine
Critical period is days 40-70 of gestation
Indolozidine alkaloid of black patch on red clover
Endophyte-Infected Tall Fescue
Poor production, fat necrosis, fescue foot, reproductive problems in
cattle and sheep
Pregnant mares have prolonged gestation, weak fola,s stillbirths,
agalactia
Ergovaline- one of the endophyte alkaloids in tall fescue
Endophyte in ryegrass may cause founderSomething to watch for...
Some combinations of grass and endophyte to be developed with..
Good yield
Disease and pest resistance
Low alkaloid level
Sainsonine and Slaframine
Swainsonine is the primary toxicant in locoweed
Ingestion of red clover infected with Rhizoctoniacauses "slobbers"
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The fungus produces the toxin, slaframine
Leucaena Forage and Mimosine
Leucaena is a tropical legume forage, high in protein, good ADF an
dNDF but has toxin mimosine
Mimosine is a depilatoryand it metabolizes to 3,4-DHP which is a
goitrogen
Brassica and SMCSO
Brassicas (kale, rape, broccoli, cauliflower, turnips, etc.) contain S-
methyl cysteine sulfoxideSMCSO interferes with iodine uptake, causing thyroid cells to swell
(goitrogen)
Fructan
Selection for high sugar levels in cool season grasses has
increased fructan
Fructan is similar to starch and contributes to laminitis
Fructan is made from fructose and glucose
Accumulates in plant vacuoles, especially in stemLength of chain varies
Fermentation product of gut bacteria is lactic acid, which lowers pH
of hind-gut, rendering it an unfavourable environment for gram
negative bacteria which subsequently die, and during their death
release toxinsinto the bloodstream. It is these toxins which are
thought to be involved in initiating the onset of diet-induced
laminitis.
Try to keep Non Structural Carbohydrates in forage