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.
