EFFECTS OF ROASTING OF LUPINS (LUPINUS-ALBUS) AND HIGH-PROTEIN VARIETY OF SOYBEANS (AC-PROTEUS) ON CHEMICAL-COMPOSITION AND IN-SITU DRY-MATTER AND NITROGEN DISAPPEARANCE IN DAIRY-COWS

The effects of roasting of lupins or soybeans were evaluated for chemi cal composition and in situ rumen degradability. Sweet white lupins (L upinus albus) and a high protein variety of soybeans, AC Proteus (HPSB ), were roasted in an electric roaster at a temperature of 300-degrees -C with a residence time of 1, 2, 3, or 4 min. Raw and roasted samples were analysed for total nitrogen, acid detergent insoluble nitrogen ( ADIN) and protease insoluble nitrogen (PIN), and available rumen by-pa ss protein (RBP) was determined. In situ degradability of dry matter ( DM) and nitrogen (N) was determined using Dacron bags in the rumen of three ruminally cannulated dry cows. Soybean meal (SBM) served as a co ntrol treatment. Total N content of lupins and HPSB was not affected b y roasting. Heat treatment increased linearly (P<0.02) the PIN content of lupins and HPSB. ADIN content of lupins and HPSB significantly inc reased with increasing roasting time from 1 to 4 min. Available RBP in creased more in roasted HPSB than in roasted lupins with increasing ro asting time. SBM had lower available RBP than roasted lupins or HPSB. Roasting significantly (P<0.01) reduced effective degradation of DM an d N in roasted lupins and HPSB at a calculated outflow rate in the rum en of 0.06 h-1. The effective degradation of N of HPSB or lupins at 4 min roasting was 10 percentage units lower than SBM. It can be conclud ed that roasting of lupins or soybeans is a useful tool to increase av ailable rumen by-pass protein and to reduce the effective degradation of N in the rumen of dairy cows.