Effect of extruding on ruminal disappearance and lower gastrointestinal tract digestion of white lupin seeds

Abstract

The effect of extruding white lupin (Lupinus albus 'Lublanc') seeds (WLS) at 110, 130, 150 or 180 °C on the in vitro solubility of crude protein (CP) and in sacco rumen degradation and intestinal digestion of rumen escape CP and fiber was determined. Rumen degradation was estimated by incubating nylon bags in the rumen of cows for 2, 4, 8, 16, 24 and 48 h. Extruding WLS at 110, 130, 150 and 180 °C reduced the CP-solubility by 32.8, 47.7, 58.4 and 67.5%, respectively. The effective ruminal degradabilities of CP, acid detergent fiber (ADF) and neutral detergent fiber (NDF) were evaluated assuming a ruminal outflow rate of 0.06 h−1. Heating WLS at 110, 130, 150 and 180 °C decreased the ruminal degradability of CP value: 89.8, 79.9, 65.1, 61.8 vs. 93.4% (raw), respectively; the corresponding values for ADF and NDF were: 38.4, 35.3, 34.2, 27.6 vs. 43.6% (raw) and 37.7, 33.1, 32.2, 26.5 vs. 39.4% (raw). Postruminal digestion was estimated using a sequence of ruminal in situ incubation for 4, 8 and 16 h, in vitro incubation in an acid-pepsin bath for 3 h and a mobile nylon bag technique distal to the abomasum. Extrusion of WLS decreased the degradability of CP, ADF and NDF in the rumen with a corresponding increase in the amounts digested in the postruminal sections; the whole-tract digestibility was generally unchanged. Therefore, the processing shifted the digestion of these components from rumen to the lower gastrointestinal tract. Key words: White lupin seed, in vitro solubility, rumen degradability, postruminal digestion, crude protein, detergent fiber