Effects of Lupinus alkaloids on in vitro rumen fermentation and their fate in the rumen

Quinolizidine alkaloids constitute an important group of natural products in the Fabaceae. They seem to play a role in ecological interrelationships by acting as chemical defence against phytophagous animals (nematodes, molluscs, insects, vertebrates), microorganisms (viruses, bacteria, fungi), and other competing plant species. Lupin seeds contain up to 8 g/kg quinolizidine alkaloids, which limits the utilization of lupin seeds as human food or animal feed. The in If fro effect of two alkaloids (lupanine and sparteine), at three concentrations (1, 2.5 and 5 mM), on rumen fermentation and their degradation by rumen microbes were studied. The experiments were conducted using the Hohenheim in vitro gas method in which a feed (hay) is incubated in the presence of a medium containing rumen microbes. Lupanine and sparteine decreased gas production and apparent and true digestibility at concentrations of 2.5 mM (% decrease: lupanine 12, 7, 14; sparteine 5, 4, 11 respectively) and 5 mM (% decrease: lupanine 28, 18, 27; sparteine 12, 11, 12 respectively). The 1 mM level of these alkaloids, had no effect on any of the measured parameters. Lupanine and sparteine were not degraded by incubation of up to 36 h with rumen liquor from a cow fed a roughage-based diet.