Ragwort (also known as Senecio Jacobaea) toxicity is one of the most common causes of poisoning to horses in the UK. A recent survey by the British Horse Society showed that 20% of respondents knew of a horse that had been affected. Toxicity is caused by substances in the plant called Pyrrolizidine alkaloids. The effect is cumulative and symptoms may not be seen for up to a year after exposure. The poison effects 3 main body systems - the liver, the central nervous system (brain, spine and its associated nerves) and the skin. Symptoms include weight loss, loss of appetite, depression, diarrhoea, jaundice (yellowing of the whites if the eyes and gums) and constipation. Neurological problems can be seen as wobbling and dizziness, pressing the head against the wall and the appearance of walking aimlessly. Toxic compounds can also enter the skin causing it to become particularly sensitive to sunlight resulting in crusting on white areas that looks like sun burn. This process is called Photosensitisation.
If you’re concerned your horse may have been affected please contact your vet. Blood tests can be used to confirm liver damage but cannot test specifically for the poisoning. A sample of tissue taken directly from the liver may be able to confirm the damage is caused by Ragwort. Horses diagnosed with poisoning rarely recover. Treatment is mostly supportive with nutrition to maintain condition and medications to control the symptoms.
Control of ragwort is crucial in avoiding illness. The first step is the identification of plants. For the first year of life the plant is a small dark green rosette. In subsequent years it becomes the characteristic bright yellow flowers between June and October. Ragwort cannot be entirely eliminated from the UK as it forms an important part of the ecosystem. However, the Weeds Act 1959 made ragwort control a legal obligation for owners and occupiers of grazing land. Those who keep their horses in livery and are unsure of their responsibility in ragwort control should check their contract.
Cutting of ragwort plants is only suitable in emergency short term control to prevent seeding. Cutting the stem stimulates growth and will cause the plant to re flower later in the season. If removing plants by hand, they should be pulled up or levered out by the roots. Ensure the entire root is removed as any left behind will re-grow. Ragwort is best pulled early in the summer before flower heads mature and when the ground is wet. As well as removing adult plants it is important to identify first year rosettes to prevent them seeding the next year. Ragwort is toxic to all species including humans so gloves and long sleeves should be worn. Any skin exposed to the plant should be thoroughly washed in warm soapy water. Once pulled the plants are still toxic and may still seed, in fact wilted plants are more palatable to horses. It is essential all plants are collected and placed in sealed boxes or bags. Disposal can be by incineration, rotting or removal by a waste-management company. The plants should never be composted, placed on the muck heap or transported without being properly sealed in bags.
It is possible to use herbicides as part of a ragwort control strategy although it must be considered that one application does not guarantee total removal. Most products require application in the spring to the growing rosettes and a calm dry day. When choosing a product thought must be given to the environmental implications and proximity to water sources which may become polluted. If spraying you will need a suitably trained person and the means to correctly dispose of unused chemicals. Horses must be moved off the pasture for application and for a period of time afterwards. The manufacturers of pesticides will make recommendations on when it is safe to use the pasture but it is the keeper's responsibility to ensure all dead ragwort is fully wilted before exposing to horses. For a list of approved pesticides please see pesticides.gov.uk.
Ragwort thrives in areas of poorly kept grassland so plant numbers can be reduced by improving pasture management. This includes not over-gazing, adequate manure removal and removing uneaten stale hay. Poaching the ground should be avoided wherever possible as bare patches are ideal for ragwort growth. Co-gazing with sheep can be beneficial as they are far less susceptible to ragwort poisoning than horses and will eat the young first year rosette plants.
For any advice on ragwort control or if you think your horse may be affected by poisoning contact The Arundel Equine Hospital on 01903883050.
Written by Rebecca Dobinson, BVSc, MRCVS