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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