PROTEIN AND ENERGY EVALUATION WITH RATS OF SEED FROM 11 LUPIN CULTIVARS

Six lupin cultivars from Australia and five from France were analysed for proximate constituents, energy, amino acids, trypsin inhibitor, starch, tannin and soluble and insoluble dietary fibre, and were evaluated with rats (five per cultivar) for digestibility of energy and nitrogen. Lysine content ranged from 4.50 to 5.05 g per 16 g N and methionine from 0.53 to 0.82 g per 16 g N. The Australian cultivars were consistently lower in content (dry matter (DM) basis) of methionine (0.53-0.71 g per 16 g N vs. 0.76-0.82 g per 16 g N), tannin (0.31-0.36% vs. 0.55-0.69%), fat (6.82-7.40% vs. 11.02-12.11%) and gross energy (19.66-20. 10 MJ kg-1 vs. 20.85-21.17 kJ kg-1). All cultivars were high in soluble dietary fibre (mean for Australian cultivars 16.3 g per 100 g DM; mean for French cultivars 13.3 g per 100 g DM). No trypsin inhibitor was detected in any sample. In tests with rats, methionine supplementation had no effect on true protein digestibility (TD) but improved biological value (BY) by 4.6-19.7%. Energy digestibility, which ranged from 60.3% to 76.15%, was consistently higher in the French cultivars; it was not affected by methionine supplementation.