Panicum species

Abstract

DISTRIBUTION: Grows in fertile, damp soil, usually in the shade.

BOTANICAL DESCRIPTION: General: Annual or perennial tufted grass species growing from rhizomes. Leaves: Leaf sheath is often hairy and leaf blades are rolled. Flowers: Inflorescence is an open panicle and often flushed with purple when growing in direct sunlight. September - March.

TOXIC PRINCIPLE: • Similar to Geeldikkop. • Toxic principle: Steroidal saponins.

MECHANISM OF ACTION: • Hydrolysis of a steroidal saponin to diosgenin with subsequent hydrogenation, reduction and epimerisation, which occurs in the rumen. • Epismilagenin and episarsasapogenin amongst others, are formed, absorbed and conjugated with glucuronic acid in the liver to be excreted via the bile. • However, the epismilagenin and episarsasapogenin glucuronides bind to Ca2+ to form an insoluble salt, which precipitates to form biliary crystals which obstruct the bile ducts.

SYNDROMES: Dikoor.

SYSTEMS AFFECTED: Liver.

CLINICAL SIGNS: Dikoor – similar to geeldikkop – distribution Free State and Highveld. Sheep condition mainly. Usually milder disease (probably due to farming practice – detected earlier and kept in shade etc.).

NECROPSY: Identical to Geeldikkop - Clefts, etc. identical Macroscopical findings: • Icterus and photosensitivity. • Liver - enlarged khaki to yellow-brown. • Chalky white sediment in bile ducts and gall bladder. • Later small pits on surface although morphology never distorted as in F.E. • Kidneys swollen and light in colour, with small green spots distributed through cortex.

HISTOPATHOLOGY: • Accumulation of crystalloid material in portal and intra- and extrahepatic bile ducts leading to partial or complete occlusion and concentric, lammellar periductal fibrosis. • Plate-like structures seen on section as clefts and on scanning EM as rose- like structures and/or debri in greater ducts. • Other pathological changes are present but are mostly secondary to this.

TREATMENT: Keep in shade. Diet low in chorophyll. Antihistamines. Corticosteroids. Cholagogues. Liver supportive treatment. Valuable animals – barrier creams and tattoo ink will protect from sunburn.