The German Equestrian Federation (FN) has suspended Olympic dressage rider, Isabell Werth, from competition for six-months after one of her mounts tested positive for a banned substance.

El Santo NRW tested positive for cimetidine at the Rhineland Championships in June 2012. The drug, which is used to treat stomach ulcers, is not banned by the FEI, but it is on the FN’s forbidden substances and prohibited medication in competition list.

Werth claims that the horse has never been given ulcer medication and was contaminated due to a faulty watering system at her barn, but the FN’s disciplinary commission said they believed this explanation was extremely unlikely and ruled that the violation occurred as the result of a breach of duty of care, and that the Werth is responsible. They also handed her a fine of €2,000.

Werth has the right to appeal the decision in the Court of Arbitration for Sport.

This marks Werth’s second suspension. She received a six-month ban in 2009, when her horse, Whisper tested positive for Fluphenazine at a CDI Wiesbaden in Germany.