Which organ system is primarily affected by Senecio in horses?

The liver is the primary organ system affected by Senecio species, commonly known as ragwort, in horses. These plants contain pyrrolizidine alkaloids, which are toxic compounds that can lead to severe liver damage when ingested. This liver toxicity manifests as hepatic fibrosis, which is a result of chronic liver injury.

Clinical signs of Senecio poisoning can include weight loss, jaundice, and in severe cases, liver failure, which can be fatal. The liver plays a crucial role in metabolizing various substances, and when it's compromised, it can lead to systemic issues affecting multiple organ systems. However, the direct deleterious effects of Senecio toxicity are predominantly seen in the liver itself, making it the organ system most significantly impacted by exposure to this plant.

Other organ systems, while they may be affected secondarily due to the liver's role in detoxification and metabolism, do not experience the primary toxic effects observed with Senecio exposure as the liver does.