Alnus glutinosa (common alder, black alder). A member of the plant family BETULACEAE.
Tree with oblong crown. Leaves are stalked, blunt or ovate with serrated edges. Male
catkins are red and yellow, tassel-like; female flowers are small, ovoid, purplish-brown.
The fruit is a dry nut surrounded by a woody, spiny involucre, bordered by two flat
wings which split open when mature.
Animals most affected
Poisoning very rare as the plant is not generally consumed. However, in periods of
food shortage or after the application of agrochemicals such as the phenoxy acids
(2,4-D, 2,4,5-T...), there is an increase in the palatability of the plant which
encourages its ingestion.
The bark contains l0-20% of tannins (related to the tannins present in oak trees).
Toxic doses not known.
followed by stiffness, ataxia, decubitus, convulsions;
paddling movements of the limbs, opisthotonos and death.
No antidote. Symptomatic care only:
adsorbents, gastrointestinal demulcents;
tranquillizers if indicated.
After a field had been sprayed with the phenoxy herbicide 2,4,5-T, some alders bordering
the area were inadvertently treated. Ten days later, a group of five cattle were
put in the field. One week later, four cows presented with severe haemorrhagic diarrhoea.
Two of the animals subsequently developed nervous symptoms: one presented with stiffness,
paddling movements of the limbs, opisthotonos and later died; the second had ataxia,
decubitus then died.
An investigation showed that the cattle had ingested large quantities of the alder
branches. Such incidents are quite common and should be taken into consideration
when chemicals such as 2,4,5-T are applied to open pasture or to land to be used
later for grazing.