In situ evaluation of the ruminal and intestinal degradability of extruded whole lupin seed nitrogen.

The effect of whole lupin seeds (Lupinus albus cv Lublanc) at 120, 150 and 195 degrees C on in situ nitrogen degradability (Dg.N) was measured by the nylon bag technique using fistulated non-lactating Holstein cows. The N degradation was evaluated in nylon bags suspended in the rumen; heating the seeds at 120, 150 and 195 degrees C decreased the Dg.N value: 83.9, 72.9 and 53.0 respectively vs 95.3% (rumen outflow rate of 0.06/h). To estimate the total N disappearing in the digestive tract, bags were incubated in the rumen for 16 h, then in a pepsin bath for 2 h and then introduced into the duodenum for subsequently recovery in feces. The whole tract degradability of N was always high, approximately 98.3%. The amounts of N which disappeared in the intestine increased from 3.1 (untreated seeds) to 15.1, 26.3 and 44.7% as the temperature rose to 120, 150 and 195 degrees C respectively. The PDIN and PDIE contents (g/kg of DM) of the raw whole lupin seeds were 224 and 84 respectively; extrusion elevated these values by 10-32% for PDIN and 57-194% for PDIE. The augmentation in the supply of dietary proteins to the postruminal parts as a result of extrusion could rapidly benefit high yielding cows.