We are reminding owners to keep their horses safe from the risk of grazing around sycamore trees as they shed their seeds. Ingestion of sycamore seeds can cause rapidly fatal illness in horses.
“With leaves still on trees now is the time to identify sycamores in the vicinity of your horse’s fields and predict the future risk,” said Lucy Grieve, Veterinary Projects Officer at BEVA “Once the leaves start to turn and then drop it will be much more difficult to spot sycamores.”
High winds can cause sycamore seeds to spread considerable distances from the tree. In the ideal world horses should be kept away from grazing around sycamores but if there is no other option then providing supplementary forage in the field will help to keep them occupied and help prevent them from ingesting seeds. It is imperative to seek veterinary attention immediately if horses that have access to sycamore seeds show any signs of illness.
Seeds (masts or helicopters) from the common sycamore tree (Acer pseudoplatanus) produce a toxin called Hypoglycin A, which can remain present in high concentrations in seedlings. When horses eat these, either by accident or because they are lacking other forage options, some individuals will develop severe and often fatal muscle damage, called atypical myopathy.
Horses with atypical myopathy may present with variable signs including:
• muscle soreness
• stiffness
• weakness
• difficulty breathing
• dullness
• lethargy
• muscle trembling
• colic-symptoms
• characteristically, brown or dark red urine.
Suspected cases should receive veterinary attention immediately. Around three quarters of affected horses will die, often despite extensive veterinary treatment but those surviving the initial period will usually go on to make a full recovery.
Acorns can also be a toxic risk to horses but tend to be easier to manage as they fall under the trees and are too heavy to spread far. Signs of acorn poisoning include:
• moderate to severe colic or colitis
• lethargy
• dehydration and dark urine which can be a result of kidney failure
Prompt veterinary attention is essential; signs may develop extremely rapidly and death can occur within a further 12-24 hours.
Horse owners are advised to take practical steps to prevent the diseases by limiting access to sycamore seeds and acorns:
• Identify trees both around grazed fields as well as those in close proximity. The characteristic maple leaf shape is easy to spot, and most people will be familiar with the oak, but if in doubt a test is available from the Royal Veterinary College as a result of work funded by The Horse Trust.
• Collect seeds or exclude horses from affected areas using electric fencing or stabling.
• Feed supplementary hay to try and prevent horses from excessive foraging for short blades of grass and inadvertent ingestion of seeds. But ensure that hay does not become contaminated by seeds.
• Don’t rashly fell trees when laden with seeds as this can cause a sudden and massive contamination of the pasture. Consider local regulations, tree protection orders and tree ownership if felling is the only option.
• Monitor horses carefully even after they have been moved from affected pasture as disease can occur up to four days after exposure.
For further information you can download the Royal Veterinary College’s fact sheet on Atypical myopathy and the British Horse Society a fact sheet on Acorn Poisoning