Every year I see it in practice:

Poisoned cows, sheep, and horses as a result of an excessive intake of gallotannins from acorns.

A toxic substance from the group of tannins.


All Oak species (Quercus spp.) are poisonous to cattle, sheep and horses. Mainly the green plant parts (young oak leaves and green acorns) are rich in gallotannins. Brown acorns pose a lower risk, although they can cause harm if eaten in large quantities.


The rumen and intestinal bacteria convert the tannins into toxic metabolites. These cause extensive damage to the blood vessels.

Often the first sign is a separation of the animal from the group. The clinical symptoms are very diverse: lethargy, loss of appetite, colic, (bloody) diarrhea, more drinking and urination, faster breathing, lower temperature, sometimes a bloody nasal discharge, edema.

Ultimately, the animals often die of kidney failure.

Not only large ruminants can get acorn poisoning, sheep too.

After acorn poisoning, they become restless, refuse to eat, suffer from constipation, colic, bloody diarrhea and a swollen abdomen. Sometimes they show a stiff gait, with later paralysis symptoms. The animals drink and urinate abnormally.


The degree of poisoning depends on the concentration. A tannin dose of 120mg / kg body weight is often deadly for calves.


Noticeable during autopsy are the edemas (fluid accumulation) in the chest and abdominal cavity, and bleeding in the kidneys.


The chance of acorn poisoning (intoxication) is greater during dry, warm summers when the acorn harvest is large and the grass is scarce.

No specific “antidote” is currently known for acorn poisoning.

So prevention is better than cure. Therefore, use fencing so that animals cannot reach the acorns or young oak leaves.

Animals on a meadow with little grass will (out of necessity) eat the acorns. Supplementary feeding is the best remedy to prevent worse!