<p>1,2-Dehydro-pyrrolizidine alkaloids (PA) and their <i>N</i>-oxides (PANO) exhibit acute and chronic toxic effects on the liver and other organs and therefore are a hazard for animal and human health. In certain regions of Germany, an increasing spread of <i>Senecio</i> spp. (ragwort) on grassland and farmland areas has been observed during the last years leading to a PA/PANO-contamination of feed and food of animal and plant origin.</p> <p>This project was carried out to elucidate whether the process of grass pellet production applying hot air drying influences the content of PA and PANO. Samples of hay (<i>n</i> = 22) and grass pellets (<i>n</i> = 28) originated from naturally infested grassland (around 10% and 30% dominance of <i>Senecio aquaticus</i>) and from a trial plot with around 50% dominance. Grass pellets were prepared from grass originating from exactly the same plots as the hay samples. The samples were analysed by liquid chromatography-tandem mass spectrometry for PA/PANO typically produced by this weed.</p> <p>The results of the study revealed that PA/PANO levels (predominantly sum of senecionine, seneciphylline, erucifoline and their <i>N</i>-oxides) in hay ranged between 2.1 and 12.6 mg kg<sup>−1</sup> dry matter in samples with 10% and 30% dominance of <i>S. aquaticus</i>, respectively. Samples from the trial plot (50% dominance) had levels of up to 52.9 mg kg<sup>−1</sup>. Notably, the hot air drying process during the production of grass pellets did not lead to a reduction of PA/PANO levels. Instead, the levels in grass pellets with 10% and 30% <i>S. aquaticus</i> ranged from 3.1 to 55.1 mg kg<sup>−1</sup>. Grass pellets from the trial plot contained up to 96.8 mg kg<sup>−1</sup>. In conclusion, hot air drying and grass pellet production did not affect PA/PANO contents in plant material and therefore, heat-dried products cannot be regarded as safe in view of the toxic potential of 1,2-dehydro-pyrrolizidine alkaloids.</p
