In a survey conducted by the BHS in consultation with the British Equine Veterinary Association, veterinary surgeons reported 284 cases of suspected or confirmed cases of liver failure in horses due to ragwort poisoning in 2002.
This is however probably a gross underestimate of the true numbers because not all horses and ponies dying of ragwort poisoning are reported to vets. The number of horses suffering what is an agonising death is probably much higher.
A BHS survey completed in 2014 focused on ragwort control and the main findings of this research were:
- 20% of the respondents knew personally of instances where horses had been suspected or confirmed as having been harmed by ragwort poisoning.
- 93% said that they take preventative measures to reduce the risk of ragwort on the land that they own, rent or manage.
- 55% of respondents had taken no action when they had seen ragwort growing on land that they did not themselves own – the main reasons being that they did not know who to contact and they did not think they would be listened to.
- 75% of respondents have not sought advice about ragwort from organisations.
- 84% of respondents reported having seen ragwort on land that is used by horses in the seven days prior to them completing the survey.
- 97-99% of respondents believed that more activity is needed with joint public/sector policy responses, including improving knowledge, the enforcement of ragwort control regulations and improving local councils’ monitoring of ragwort.
When the plant is in flower is a good time to remove and burn it. Ragwort contains pyrrolizidine alkaloids which survive drying and are therefore active in hay and straw. The mature plants are not palatable and are usually avoided by horses unless there is no other source of roughage or food in the field. The dried plant is much more palatable.
The alkaloids are metabolised in the liver to toxic pyrrole derivatives which inhibit the division of liver cells so that the liver shrinks in size and is irreversibly damaged with little prospect of repair. There is no effective treatment. The amount of plant required to cause serious damage is very small. Often euthanasia is the most humane course of action.
It is very difficult to differentiate in hay. It can resemble other plants with a thick fibrous stem and can therefore be very difficult to recognise in hay or other drier forage. The leaves are deeply dissected with ragged edges. The large flat topped yellow flower head can be clearly seen when present. It may therefore be prudent to collect a plant now and dry it so that you will recognise the different parts of the dried plant in hay should it be present.
Clinical symptoms
The symptoms of ragwort poisoning are of chronic liver disease but acute liver disease can occur:
- Abdominal pain (colic).
- Diarrhoea, constipation and straining.
- In-coordination.
- Skin photosensitisation.
- Yawning.
- Head pressing.
- Apparent blindness.
- Collapse, coma, death.
- Jaundice is not a common feature.
It is also worth bearing in mind that an individual horse, pony or donkey can develop a craving for the fresh plant leading to a rapid unpleasant death.
Treatment is difficult once liver failure has occurred. It relies on supportive therapies in the hope that the liver can regenerate. Unfortunately in most cases the liver is too damaged for this to occur, although some horses can survive.
Prevention
With the price of hay higher than usual there may be pressure to purchase hay which has been cut from pasture where ragwort has been growing. It is very difficult to differentiate in hay. It can resemble other plants with a thick fibrous stem and can therefore be very difficult to recognise in hay or other drier forage. The leaves are deeply dissected with ragged edges. The large flat-topped yellow flower head can be clearly seen when present. It may therefore be prudent to collect a plant now and dry it so that you will recognise the different parts of the dried plant in hay should it be present.
Control
Ragwort can be controlled by hand removal (pull up the roots as well – we suggest that you wear gloves – purpose designed tools are available for removing the shallow roots) before seed production or the application of herbicides and removal of the dead plants,contact Defra for advice. Animals (ragwort is toxic to all animals though ruminants are less susceptible) should be kept off sprayed pasture until the weeds are removed as the Ragwort plants are more palatable when wilted than fresh.
