Quercus robur

Abstract

DISTRIBUTION: Most common and best-known oak species in South Africa. Cultivated in colder, moister climatic areas – problematic in eastern and south western Cape and highveld of Kwazulu- Natal and Mpumalanga. Botanical description: General: Large trees. Exotic, cultivated in gardens, on farms, etc. Leaves: Deciduous. Alternate, simple, deeply lobed leaves. Slightly hairy and bright green when young. Later in the season they become smoother and darker. Fruit: Typical conical acorn and cup.

TOXIC PRINCIPLE: Hydolyzable gallotannins are converted in the rumen to gallic acid, pyrogallol and resorcinol. Green acorns are more toxic.

SYNDROMES: Tannins, Primary nephropathy, Acorn poisoning.

SYSTEMS AFFECTED: Urogenital system.

CLINICAL SIGNS: • In South Africa only bovines are affected. • Usually animals under 2 years of age most susceptible. • Develop craving. • Horses and sheep are susceptible. • Pigs thrive on it and are not susceptible. • Latent period of few days. Gastrointestinal Tract: - Inappetance, abdominal pain - Constipation - soon changes to persistent diarrhoea leading to dehydration and emaciation Urinary System: - Polyuria/anuria - Urine initially dark, haemorrhagic - later pale - Uraemic signs of kidney failure - Prognosis poor - 80% plus mortality

CLINICAL PATHOLOGY: Marked elevation of BUN and creatinine, hypoproteinaemia.

NECROPSY: Macroscopical findings: • Interstitial nephritis, enlarged, pale kidneys with small white foci, petechiae, perirenal oedema, uraemic smell. • Gastro-enteritis, oedema and multifocal ulceration of intestinal tract and even of mouth and oesophagus. • Acorns may still be present in rumen. • Fluid accumulation - under skin (anasarca) and in body cavities (ascites, hydrothorax), perirenal oedema. • Emaciation and dehydration. • Haemorrhages in different organs.

TREATMENT: • Withdraw from toxic acorns • Ruminotorics • Fluid therapy • Symptomatic treatment of diarrhea.

PREVENTION: • Do not feed acorns only, use as supplement. • Valuable feed. • Ca(OH) 2 (Slake lime) 10-15% in balanced supplementary feed prevents intoxication, because calcium complexes with tannins forming insoluble complexes preventing their absorption. • Boiling or soaking to leach out tannins.