In Sacco Evaluation of Rumen Protein Degradation Characteristics and in vitro Enzyme Digestibility of Dry Roasted Whole Lupin Seeds (Lupinus albus)

Abstract

The effects of dry roasting whole lupin seeds (lupinus albus, WLS) at 110, 130 or 150°C for 15, 30 or 45 minutes on the in sacco rumen degradation characteristics, optimal heating conditions of time and temperature and in vitro enzyme digestibility were determined. Ruminant degradation characteristics (RDC) of crude protein (CP) of WLS were determined by in sacco technique in dairy cows. Measure RDC were soluble (S), undegradable (U), potentially degradable (D) fractions, lag time (TO) and rate of degradation (Kd) of insoluble but degradable fraction. Based on measured RDC, percentage bypass CP (%BCP) and bypass CP (BCP in g/kg, DM) were calculated. Degradability of CP was significantly reduced by dry roasting (p<0.001). The interaction of dry roasting temperature and time had significant effects on D (p<0.05), Kd (p<0.01), U (p<0.01), %BCP (p<0.001) and BCP (p<0.001) but not on S (p=0.923>0.05). With increasing time and temperature, S, D, Kd and U varied from 31.8%, 67.4%, 10.3%/h and 0.8% in the raw WLS (RWLS) to 27.1%, 35.8%, 3.6%/h, 38.4% in 150°C/45 min, respectively. All these effects resulted in increasing %BCP from 25.9 in RWLS to 61.0% in the 150°C/45 min. Therefore BCP increased form 111.2 to 261.2 g/kg DM, respectively. Both %BCP and BCP at 150°C/45 min increased nearly 2.5 times over the RWLS. The effects of dry roasting on %BCP and BCP seemed to be linear up to the highest value tested. Although RDC had been altered by dry roasting, the In vitro perpsin-cellulase digestibility was generally unchanged. It was concluded that dry roasting was effective in shifting CP degradation from rumen to the lower gastrointestinal tract to potential reduce unnecessary N loss in the rumen. It might be of great value in successfully synchronizing the rhythms of release of nitrogen and energy in the rumen, thus achieving a more efficient fermentation of diets with high proportions of lignocellulosic resources. To determine the optimal dry roasting conditions, the digestibility of each treatment in the cows will be measured in the next trial using mobile bags technique.