In vitro N degradability and N digestibility of raw, roasted or extruded canola, linseed and soybean

The N degradability and N digestibility of raw, roasted or extruded oilseeds were studied using an in vitro enzyme method. The N degradability and N digestibility of canola, linseed and soybean were calculated based on the proportional difference in N remaining after incubation and the initial N content. Heat treatments increased the undegradable N fraction of linseed and soybean, whereas that of canola was decreased by extrusion. Heat treatments did not decrease the N digestibility of the oilseeds compared to raw samples. The high N digestibility and lower acid detergent insoluble N values of heat treated oilseeds indicated no indigestible complexes were formed. In conclusion, roasting or extrusion can be used to increase the undegradable N fraction of linseed and soybean to increase the dietary protein availability for digestion in ruminants, but was less effective for canola. The present heat treatments did not damage the protein or affect the N digestibility of the oilseeds.