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

Abstract

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.