Effects of a supply of raw or extruded white lupin seeds on protein digestion and amino acid absorption in dairy cows.

Four cannulated, lactating cows were used to determine the effects of extruding white lupin seeds (WLS) on intraruminal CP degradation and absorption of AA from the small intestine. Raw lupin seeds (RWLS) and extruded lupin seeds (EWLS) were fed in diets containing 15.5% CP and composed of 22.4% WLS, 55.9% corn silage, 10.1% maize grain, and 10.6% Italian ryegrass on a DM basis; WLS provided approximately 50% of the total dietary CP. Spot samples of digesta were collected from the proximal duodenum and terminal ileum during 72 h. Chromium EDTA, YbCl3, and purines were used as liquid, particulate, and bacterial markers, respectively. Because of the extensive ruminal degradation of dietary N with the RWLS diet compared with the EWLS diet (64.2 vs 38.8%), less total AA flowed to the duodenum (1,748 vs 2,347 g/d), and because of the decrease of availability (67.2 vs 79.0% of entering), absorption from the small intestine was lowest with this diet (1,175 vs 1,855 g/d). The apparent digestion of individual AA in the small intestine (percentage entering) ranged from 46.5 to 88.4 when cows consumed RWLS and from 58.9 to 94.4 when they were fed the EWLS diet. Among the diets, apparent absorption of histidine, lysine, glycine, and serine were higher than those of other AA; also, valine, alanine, and proline showed intestinal absorptions that were somewhat lower than those of the remainder of the AA.