Later this summer we may expect to see the bright yellow flowers of the common ragwort (Senecio jacobaea) and, knowing how toxic it is to horses and ponies we will need to remove it from pasture. But waiting for ragwort to flower before getting rid of it is a mistake and it is much better to prevent the spread of the weed by digging it up by the roots in the spring when it is still a green rosette.
Ideal solitary exercise during COVID-19 lockdown
In the current COVID-19 pandemic lockdown, searching your horse’s field for the tell-tale rosettes (see main picture above) armed with a ragwort fork is very worthwhile and suitably solitary exercise.
Because of its bitter taste, horses and ponies are only likely to eat ragwort if pasture is meagre. In hot, dry months grass pasture can deteriorate rapidly and clumps of yellow ragwort will eventually attract hungry horses. An even greater danger lurks in poor quality hay or haylage containing dried ragwort which is much more palatable to horses.
The poisonous pyrrolizidine alkaloids in ragwort cannot be processed by the liver and will accumulate, compromising the liver cells. Over time the loss of functioning liver cells seriously reduces liver function. Outward clinical signs are frequently not evident until significant loss of liver function and often, by the time the poisoning is diagnosed, it is too late for effective treatment.
Symptoms and diagnosis
Symptoms of ragwort poisoning depend largely on the length of exposure to the plant and its toxins. They include lethargy, weight loss, diarrhoea, colic, depression, skin lesions from photosensitisation and odd behaviour with head pressing, aimless walking, circling and seizures. The abnormal behaviour results from the liver failing to detoxify the blood, the remaining poisons spreading throughout the horse to the brain, resulting in abnormal behaviour, known as hepatic encephalopathy.
Diagnosis is made on presentation of clinical signs in conjunction with a blood test and, if a liver problem is highlighted, liver ultrasonography and a biopsy will confirm if ragwort poisoning is evident. Not all liver problems are caused by ragwort poisoning and usually the biopsy will be the technique which secures a definitive diagnosis.
Ragwort poisoning is non-reversible, and treatment is only to support the animal affected. Dietary changes and vitamin supplementation can help in management, but the key to dealing with ragwort poisoning is not to let it happen in the first place – there is no safe level of ragwort consumption!