Acorn poisoning


This year acorns appear to be particularly abundant, which has been posing increased risk of acorn poisoning in livestock and equines. Acorns are very toxic to most livestock and when eaten in large enough quantities can be fatal. Equines, cattle and sheep most commonly affected. Pigs are more tolerant and poisoning is rare. NADIS data shows that acorns are one of the most common causes of plant poisoning especially in years when acorns are abundant. As the autumn continues with stronger winds and gales the problems can increase.

Some suggest that 2022 could be a mast year due to the stress of the summer droughts; mast years normally occur every 5-10 years and during these years’ trees will produce a bumper crop of fruits and seeds.


It is believed that acorn’s toxicity comes from their tannin content, Acorns contain gallotannin. In the rumen, gallotannin is broken down to gallic acid and tannic acid. Tannic acid causes ulcerations in the mouth, the oesophagus, and the rest of the intestines. It also damages the kidneys, and it is kidney failure which causes the majority of deaths associated with acorn poisoning. In live animals, blood and urine tests can identify those with kidney failure.

Once kidney damage has occurred prognosis for the individual is poor, with mortality rates as high as 70%. The symptoms of acorn poisoning are progressive and begin with inappetatnce and constipation, which is followed by small quantities of dark coloured faeces, potentially containing blood. Animals with acorn poisoning may display symptoms within hours or it may take several days after eating acorns.

Acorn poisoning will generally affect only a few animals in the herd, as acorn poisoning only occurs if animals consume large amounts of acorns (which will only occur in animals who develop a taste for them). As tannins concentrate in milk fast-growing youngstock on heavy-milking dams will often be the first animals to show signs.


The symptoms of Acorn Poisoning can include the following:

Constipation initially, followed by black watery diarrhoea. (Straining to pass faeces and urinate is very common)


Abdominal tenderness


Rapid weight loss

Loss of appetite



Sudden death can occur (although poisoning generally occurs over a period days)

Weakening, collapse and death (usually within seven days of the onset of signs)

The animals have a normal temperature in most cases

Acorns may cause birth defects if eaten in sufficient quantities by pregnant individuals.


There is no specific treatment for acorn poisoning and thus prevention is key. If possible, try to limit access to fields with oak trees during autumn, but if this is not possible then fence off oak trees to limit access and frequently clear acorns, particularly after windy weather. Livestock who have access to sufficient, palatable feed are less likely to eat acorns so ensure that animals in fields with lots of oak have access to sufficient forage.

Good supportive therapy is the only treatment available. Fluid therapy orally and intravenously will help keep the kidney functioning and broad-spectrum antibiotics prevent secondary infection. In  the early stages a single dose of a laxative mineral oil may help.

Farmers suspecting acorn poisoning in their stock should remove the animals from the source, give them plenty of water and contact a vet immediately.