AbstractThe major alkaloids of lupin plants producing crooked calf disease were identified by tandem gas chromatography‐mass spectrometry and infrared analysis. The gas chromatography peak invariably present in teratogenic plants proved to be anagyrine. A minor but irregular contaminant of the peak was α‐isolupanine. Other alkaloids present but apparently not associated with crooked calf disease were lupanine and two others that were probably epimethoxylupanine and 5,6‐dehydrolu