Evaluation of raw and roasted lupin seeds as protein supplements for lactating cows

15 multiparous Holstein cows in mid to late lactation were fed on lucerne silage and a concentrate diet (barley 747, maize 200 and molasses 30 kg/t) supplemented with soyabean meal (control) or raw or roasted lupin seeds in a Latin square arrangement consisting of three 4-week periods. Chemical composition, in sacco digestibility and in vivo rumen fermentation characteristics and digestibility were determined to evaluate the suitability of lupins as protein supplements. The total nitrogen content of raw and roasted lupins (5.6 and 6.5% DM, respectively) was lower than that of soyabean meal (8.15% DM). The undegradable CP fraction, estimated from in sacco digestibilities, was 36.0, 37.7 and 44.7% for soyabean meal, raw and roasted lupins, respectively. Acid detergent insoluble N was similar in raw and roasted lupins (0.09 and 0.12, respectively) suggesting roasting caused minimal protein damage. Rumen fermentation and whole tract digestibility of nutrients was not different between cows fed on soyabean meal and lupins. Cows fed on roasted lupins had higher milk yield than those fed on raw lupins (26.7 and 24.7 kg/day, respectively). The milk fat of cows fed on lupins had higher concentrations of long chain fatty acids than that of cows fed on soyabean meal..