Ragwort Poisoning in Donkeys

Ragwort poisoning is a toxic liver disease caused by pyrrolizidine alkaloids (PAs) found in ragwort and related plants in the Senecio/Jacobaea group. In equids, these toxins are metabolized in the liver and can damage liver cells over time. The injury is often cumulative, which means a donkey may eat small amounts over weeks or months before obvious illness appears.

This is one reason ragwort poisoning can be so frustrating for pet parents. A donkey may seem normal for a long time, then develop signs only after a large portion of liver function has already been lost. Once scarring and chronic liver failure develop, the damage may be permanent.

Fresh ragwort is bitter, so many equids avoid it when good forage is available. The risk rises when pasture is overgrazed, forage is limited, or ragwort is dried into hay, because the plant becomes harder to recognize while remaining toxic. Donkeys can also be exposed to other PA-containing weeds, so your vet may discuss the broader category of pyrrolizidine alkaloid poisoning, not only common ragwort.

The cause is ingestion of ragwort or other pyrrolizidine alkaloid-containing plants. Common ragwort and tansy ragwort are the best-known examples, but several related weeds can cause similar liver injury. The toxic compounds are converted in the liver into reactive metabolites that damage liver cells and interfere with normal cell division.

Exposure usually happens in one of three ways: grazing contaminated pasture, eating dried ragwort in hay, or consuming the plant when forage is scarce. Dried ragwort is especially risky because it remains toxic but loses some of the bitter taste that might otherwise discourage eating.

Pasture conditions matter. Overgrazed fields, poor-quality forage, heavy weed pressure, and hay harvested from infested land all increase risk. Donkeys that live on rough grazing or are offered mixed, lower-quality hay may be exposed without anyone realizing it.

Not every exposed donkey becomes critically ill, and the amount eaten, duration of exposure, and overall liver reserve all affect the outcome. Still, because PA damage is cumulative and often irreversible, even repeated low-level exposure is important to discuss with your vet.

Diagnosis starts with a careful history. Your vet will ask about pasture weeds, hay sources, recent forage shortages, weight loss, skin changes, and any neurologic signs. In equids, bloodwork is often the first step to look for evidence of liver injury and reduced liver function. Tests may include liver-associated enzymes such as GGT, SDH, or GLDH, plus bilirubin, bile acids, albumin, and sometimes clotting tests or ammonia depending on the case.

Your vet may also recommend ultrasound to assess liver size and appearance and to look for other causes of illness. Blood tests can strongly suggest liver disease, but they do not always identify the exact cause. That is why exposure history is so valuable.

In some donkeys, a liver biopsy is the most useful way to confirm chronic toxic liver disease and estimate severity. Biopsy can help distinguish PA toxicity from infectious, inflammatory, or other toxic causes of liver disease. Your vet will weigh the benefits against the risks, especially if clotting is impaired.

If a donkey dies or is euthanized, necropsy and histopathology can provide a definitive answer and help protect other animals sharing the same pasture or hay. That information can be very important for herd-level prevention.

Prevention centers on pasture management and forage quality. Walk fields regularly and learn to identify ragwort at different growth stages, not only when it is flowering. Remove plants before they seed, and keep donkeys off contaminated areas until the plants are fully cleared. If herbicides are used, follow label directions and your vet or agronomy professional’s advice, because wilted toxic plants may still be eaten.

Check hay carefully, especially if it comes from weedy or unfamiliar sources. Dried ragwort remains toxic, and once it is baled it can be difficult to spot. Buying from reputable forage suppliers and inspecting each batch can lower risk.

Good grazing management also helps. Avoid overgrazing, provide enough safe forage, and rotate pastures when possible. Hungry equids are more likely to sample plants they would normally avoid. Donkeys on sparse pasture may be at particular risk if weed control is poor.

If one donkey is affected, think beyond the individual animal. Review the whole group’s pasture, hay, and feeding setup with your vet. Early blood screening for exposed herd mates may be worth discussing, especially when the source of contamination is confirmed or strongly suspected.