Feed refusal in fattening bulls because of maize silage contamination by Jimson weed (Datura stramonium)

A sudden decrease in feed intake (within 24 hours) without an impaired general condition occurred on a bull-rearing and -fattening farm in western Germany in December 2017. One day later, some of the bulls displayed signs of ruminal tympany (free gas bloat) and the reduction in feed intake became more severe. The maize silage was recognized as the cause of the observed symptoms, because clinical signs first appeared after taking the silage from a different localization within the bunker silo. Maize in this particular section was harvested from a separate area previously affected by wind damage (numerous bent maize plants), where no crop protection (herbicide application) was performed. Fruits and seeds of Jimson weed were identified in the incriminated maize silage samples. Following replacement of the contaminated parts of the maize silage with non-contaminated material and treatment of the clinically affected animals (anti-tympanic medication plus live yeast preparation), the feed intake returned to the normal level and the affected animals recovered within 6 days. The cause of the symptoms was probably the anti-nutritive properties of Datura stramonium that affect the motor function of the gastrointestinal tract.