This document describes a method for the quantitative determination of pyrrolizidine alkaloids (PA) in complete and supplementary feed and in forages by liquid chromatography tandem mass spectrometry (LC-MS/MS) after solid phase extraction (SPE) clean-up. The method has been successfully validated in a collaborative trial for the matrices complete feed for horses, supplementary feed for horses, supplementary feed for rodents, hay, alfalfa and grass silage. Validation was carried out for the PA and concentrations ranges listed in Table 1. It was demonstrated that the PA isomeric pairs senecivernine and senecionine as well as senecivernine-N-oxide and senecionine-N-oxide cannot be determined individually due to insufficient chromatographic separation. However, the sums of the individual PA of the isomeric pairs were quantified with sufficient reproducibility. Co-elution of other PA-isomers not included in the scope of the method shall be taken into account. A list of potentially co-eluting isomers is presented in Annex E. Although the calibration range of the method protocol is specified from 10 ¼g/kg to 300 ¼g/kg, the results of the collaborative study showed, that the dilution of sample extracts with blank sample extracts enables for the quantitation of concentrations exceeding the calibration range. Satisfactory reproducibility was achieved when quantifying up to 1428 ¼g/kg for individual PA and up to 887 ¼g/kg for the sum of isomeric pairs.