Amaranthus retroflexus (red wheat). Related species: A. viridis (green
amaranthus). A member of the plant family AMARANTHACEAE. Stout, erect plant with
a hairy red stem, ovate leaves at its base and leafless above. Small red flowers
in dense spikes, made up of many small cymes. Indehiscent, unilobular fruit.
Animals most affected
Cattle, sheep, (horses, pigs, goats, rabbits).
Direct ingestion of the plant is rare, even in times of food shortage or drought.
Poisoning occurs more commonly following ingestion of forage or contaminated silage
(mainly maize silage). Problems develop when ingestion has taken place over several
The plant is rich in oxalic acid (especially in the leaves). Variable content (often
very high) of nitrates (0.2-1.5%).
Toxic doses not well known.
600 g taken for several days (5-7)
several kg per day for several days
After 410 days of ingestion:
pigs: trembling, weakness in the hind quarters, ataxia, paralysis, coma and death;
cattle: tremor, paralysis;
rabbits: paralysis, followed by sudden death.
Perirenal oedema (in pigs, sheep, goats, cattle) with subcapsular petechiae, renal
degeneration and necrosis;
ascites with a lemon-yellow serous fluid (in rabbits);
oedema of the kidneys, petechiae on the kidney surface.
No antidote. Prevent further ingestion of the plant (within 48 hours) to avoid fatalities.