RAW OR ROASTED LUPIN SUPPLEMENTATION OF GRASS-SILAGE DIETS FOR BEEF STEERS

Raw or roasted lupins were evaluated as protein supplements in rations for growing and finishing beef steers. Lupins were roasted in a flame roaster with an exit temperature of 105-degrees-C. The effect of heat ing on protein solubility and rumen degradability of lupin was evaluat ed by chemical and Dacron bag procedures. The solubility of N in buffe r was reduced from 69.8% in raw lupin to 35.8% in roasted lupin. Effec tive degradability of crude protein (CP) and rate of CP degradation pr edicted by the Dacron bag procedure were lower for roasted lupin (82.3 % and 9.2% h-1, respectively) than for raw lupin (86.7% and 11.9% h-1, respectively). Heat damage measured by acid detergent insoluble N did not differ between raw (3.31% of total N) and roasted lupin (3.46% of total N). Twenty-eight Charolais cross steers with an average weight of 23 5 kg (+/- 35 kg) were fed grass silage only (SIL) or silage plus supplements, to supply CP at 6.5% of the silage dry matter intake (DM I), with raw lupin (RL), roasted lupin (ROL) or soybean meal (SBM) as the source of supplementary protein. When the steers reached 330 kg li veweight they were placed on a finishing diet of chopped hay, barley a nd protein supplements at a rate of 4.5% of barley DMI. In the growing phase, steers fed RL, ROL or SBM had significantly higher (P < 0.05) daily gains than steers fed silage alone. Steers fed the SBM diet had significantly higher daily gains than RL, and steers fed ROL had inter mediate gains. Daily gains of steers fed raw and roasted lupin were no t significantly (P> 0.05) different. Silage DMI was significantly lowe r on diets supplemented with RL and ROL compared with SIL. In the fini shing phase, there were no significant differences in daily pin, carca ss weight, dressing percentage, loin eye area or DMI among the diets. Heat treatment of lupins decreased solubility and ruminal degradabilit y of CP. Growth performance of beef steers fed roasted lupin was simil ar to that of steers fed SBM.