Ergot alkaloids

Abstract

FUNGI, GRASSES AND SEDGES INVOLVED: Festuca spp. (Neotyphodium coenophialum) Lolium spp. (Claviceps purpurea) Cyperus esculentus (Clacviceps cyperi).

DISTRIBUTION: Cyperus esculentus Yellow nutsedge (English), Geeluintjie (Afrikaans). Grows in moist, disturbed places. Festuca spp. Fescue grass (English / Afrikaans). Lolium spp. Annual rye grass (English), Eenjarige raaigras (Afrikaans).

BOTANICAL DESCRIPTION: Cyperus esculentus Yellow nutsedge (English), Geeluintjie (Afrikaans). General: This grass-like herb has perennial rhizomes with roundish tubers. Grows up to 600 mm. The annual aerial stems are 3-angled. Young plants are yellowish-green. Leaves: Shiny leaves that look like grass. Flowers: Branched head with 3 - 5 leaf-like bracts and light brown spikelets in clusters. July - May. Festuca spp. Fescue grass (English) Swenkgras (Afrikaans). General: This is a tufted perennial grass. Leaves: Leaves often have a small lobe or ear at the base, and old leaf sheaths usually split into fibres. Flowers: The inflorescence is an open or contracted panicle. The spikelets are laterally flattened. Lolium spp. General: An annual, dense, tufted, soft grass. Leaves: The leaves are green and shiny and the culms usually unbranched. Flowers: The inflorescence is flat with the spikelets evenly arranged on either side of the central axis. The size of the awns is up to 10 mm, which distinguishes it from Lolium perenne.

TOXIC PRINCIPLE: The Claviceps spp. form ergots, which contain different ergot alkaloids of which ergotamine and ergocryptine are the most important. • The endophyte Neotyphodium coenophialum also produces ergot alkaloids such as ergovaline. Mechanism of action: • The ergot alkaloids induce peripheral vasoconstriction, which prevents heat loss and results in hyperthermia (summer syndrome) during hot weather and hot spells. Not seen during cool weather. • During winter the existing vasoconstriction is exacerbated causing ischaemia of the extremities (tail, feet, ears), necrosis and dry gangrene. • A decrease in serum prolactin has also been reported.

SYNDROME: Summer syndrome, Fescue foot.

SYSTEMS AFFECTED: Cardiovascular system.

CLINICAL SIGNS: Clinical signs of hyperthermia: • High morbidity • Hyperthermia • Breathing with an open mouth, with the tongue protruding, • Increased respiratory rate • Excessive salivation • Inappetance • Excessive intake of water with resulting polyuria • Overgrowth of hair in the summer • Reddish-brown discolouration of black patches in Holsteins. • Cattle look for shade and attempt to cool themselves by standing or lying in water or even in the dampness caused by the excessive urination. • Drop in milk production (a decrease in serum prolactin concentration as well as a decreased feed intake). • Reproductive problems (prolactin is required for the maintenance of the corpus luteum).

NECROPSY: Nothing specific.

TREATMENT: Fescue foot: Dry gangrene (during winter). For Summer Syndrome: • Cool down the animals (hose down or spray with water), keep them in shade. • Dopamine-receptor blockers i.e. domperidone, phenothiazine tranquillizers (?).

CONTROL: • Avoid feeding screenings. • Permissible level <0,05% m/m. • Prevent seeding of ryegrass by heavy grazing in early growth stage or the use of herbicides. • Clear lands of nut sedge, eradicate with herbicides. • Cut maize stalks higher when making silage. • Analyse fescue grass to ascertain if endophytes are present and/or producing ergot alkaloids. • Limit the intake of fescue especially during seeding.