Nutritive value of raw and roasted sweet white lupins ( Lupinus albus) for lactating dairy cows

Abstract

Nine multiparous cows in early lactation were fed alfalfa silage ad libitum twice daily, a grain-based concentrate five times daily, and one of three protein sources five times daily. Supplemental proteins were soya-bean meal, raw coarse-ground sweet white lupins or roasted coarse-ground sweet white lupins. Roasting of lupins increased the calculated undegraded intake protein (UIP) proportion from 7.2 to 33.3% of total nitrogen. Intake of dry matter and organic matter was lower for lupin-supplemented cows, but intake of neutral detergent fibre was similar for all cows. Production of milk, and milk components, was similar among treatments although milk protein concentration was lower, and milk protein yield tended to be lower, for lupin-supplemented cows. Cows on all diets used dietary protein much more efficiently than calculations based upon National Research Council recommendations would suggest. Although lupin oil only comprised 1.1–1.2% of dry matter intake, changes in milk composition were typical of those associated with fat feeding as de novo synthesis of C 10 to C 16 fatty acids was suppressed, transfer of long-chain fatty acids was increased and protein percentage was decreased in milk from lupin-supplemented cows. Roasting appeared to increase protection of lupin oil from ruminal hydrogenation, as evidenced by increased concentrations of long-chain fatty acids in milk from cows supplemented with roasted lupins. The changes in fat composition are positive for the public perception of a more hypocholesterolemic milk fat, but the decrease in protein percentage is a concern both for the manufacture of milk products and with respect to changes in milk pricing formulae that assign a higher value to milk protein than to milk fat.