Vets Issue Seasonal Reminder for Acorn and Sycamore Poisoning

The British Equine Veterinary Association (BEVA) is reminding horse owners of the dangers posed to horses by the ingestion of sycamore seeds and acorns. Both can be fatal if eaten but, fortunately, there are steps that can be taken to reduce the risk.

High winds can cause sycamore seeds and acorns to spread considerable distances from the tree. In the ideal world horses should be kept away from grazing around sycamores but this is not always possible, or yard owners and horse owners may not even realise that they have Oak or Sycamore trees present on or close to their grazing.

Sycamore danger

In the case of the sycamore, it’s the seeds and seedlings that present the greatest threat to horses, as both contain a highly poisonous toxin called Hypoglycin A. With the familiar ‘helicopter’ seeds and also seedlings often present on grazing land, it’s easy for horses to consume them either by accident or because there is little else available to eat, and this can have fatal results.

The best preventative action to take is to graze horses away from sycamore trees but, if this isn’t possible, offering supplementary forage can help by keeping the horses occupied and away from the trees. Unfortunately, due to their design, the seeds, which use airborne dispersal, can spread quite a distance from the parent tree, especially in high winds, so it’s advisable to be vigilant to their presence even if there isn’t a tree adjacent to the field.

BEVA Veterinary Projects Officer Lucy Grieve said: “With leaves on trees, now is the time to identify sycamores in the vicinity of your horse’s fields and predict future risk. Once the leaves start to turn and then drop, it will be much more difficult to spot sycamores.”

Sycamore ingestion can lead to a severe and often fatal muscle damage known as atypical myopathy. Symptoms include…

• muscle soreness
• stiffness
• weakness
• difficulty breathing
• dullness
• lethargy
• muscle trembles
• colic symptoms
• brown or dark red urine

If sycamore poisoning is suspected, veterinary attention must be sought immediately. Sadly, around 75% of affected horses will die but those who survive the initial period usually make a full recovery.

Acorn danger

Another tree that can cause problems at this time of year is the oak, which sheds acorns – as well as leaves and twigs – containing tannic acid that, again, has a toxic risk to horses. Acorns are easier to manage than sycamore, as they are heavy and tend to fall under and around the tree rather than being spread on the wind, which means contaminated areas are easy to spot. Acorns also have a bitter taste, so horses are unlikely to eat them unless there’s limited grazing but there is anecdotal evidence to suggest some horses develop a ‘taste’ for them and can even seek them out.

The susceptibility to acorn poisoning varies in each individual horse but signs of it include…

• moderate to severe colic or colitis
• lethargy and depression
• dehydration and dark urine due to kidney failure
• constipation
• diarrhoea containing blood
• mouth ulcers
• acorn husks in droppings

Again, urgent veterinary attention is vital, as signs can develop quickly, and death can occur within 12-24 hours.

Preventative action

As well as monitoring horses for signs of poisoning, there are steps that can be taken to limit access to sycamore seeds and acorns…

1. Identify trees in and near grazed fields. The leaves of both trees have a distinct appearance and, if in doubt, a test is available from the Royal Veterinary College as a result of work funded by The Horse Trust.
2. Collect seeds and acorns.
3. Exclude horses from affected areas by using electric fencing, alternative grazing or stabling.
4. Feed supplementary hay to discourage horses from eating grass that could include the presence of seeds. Ensure the hay does not become contaminated with seeds, however.
5. Don’t fell trees when laden with seeds, as this can lead to sudden and massive contamination of pasture – there are also felling regulations and protection orders to consider.
6. Monitor horses carefully after removal from an affected field, as signs of poisoning can take up to four days to become apparent.

Remember, if your horses are showing any abnormal signs in their behaviour, activity or general wellbeing, and may be at risk from poisoning, ^prompt veterinary attention is essential; signs may develop extremely rapidly and death can occur within short time frames in severe cases.

For further information on atypical myopathy, click here.

For more information on acorn poisoning, click here.