Alkaloids
The bitter earlier varieties of lupins contained a toxic alkaloid and were not recommended for animal feeding unless the alkaloid was removed by soaking in water. The newly obtained sweet (alkaloid-free) varieties, which can be distinguished by taste and smaller growth, are palatable to stock. The alkaloid content of yellow lupin seeds ranged from 0.72 to 1.53 g/kg DM in Poland, depending on cultivars and cultivation conditions (Lubowicki et al., 2005; Niwińska, 2001). Alkaloid content varies upon climatic factors such as droughts that can have a major influence on the accumulation of secondary metabolites: over 6 years, the alkaloid content of yellow lupin varied from 1.07 to 1.48 g/kg DM (Lubowicki et al., 2005). The alkaloid content raised concern in piglets over a dietary content of 20 mg/kg in Australia, and over 120 mg/kg in Poland (Godfrey et al., 1985; Buraczewska et al., 1993).
Oligosaccharides
Lupin seeds contain significant levels (from 7 to 20%) of oligosaccharides of the raffinose family (Saini, 1989). Alpha-galactosides levels can reach up to 20% in the seeds of blue or yellow lupin species (Saini, 1989). The oligosaccharide level may depend on variety but also on conditions of cultivation and harvest (Pisarikova et al., 2009).