Degradation in the rumen of lupin (Lupinus albus L.) and pea (Pisum sativum L.) seed proteins: Effect of heat treatment (original) (raw)

2001, HAL (Le Centre pour la Communication Scientifique Directe)

The extent to which rumen soluble nitrogen can contribute to the intestinal protein¯ow is unknown. Therefore, a study was carried out to assess simultaneously the kinetics of: (1) protein disappearance from rumen bags; (2) the amount of various N products in the rumen¯uid contents: total nitrogen (N), ammonia nitrogen (NH 3-N), non-ammonia nitrogen (NAN), true protein (protein-N); (3) the electrophoretical characteristics of the protein in feeds, bag residues and ruminal¯uids. Measurements were made on four sheep fed successively with hay alone (basal) or 60% hay and 40% of (white lupin seeds,`Are Ás' variety untreated or extruded) or 65% hay and 35% pea (`Baccara' variety, unextruded or extruded). These seeds differed in their effective nitrogen degradability (DegN) assessed by an in situ method which gave results of, respectively, 0.954, 0.682 for control and extruded lupin (clupin and extlupin) and 0.657, 0.697 for control and extruded pea (cpea and extpea). In the ruminal¯uid, the various nitrogen forms (N, NH 3-N, NAN, protein-N) evolved differently depending whether the diet contained lupin or pea. The N contents were higher in the ruminal¯uid of the diets containing clupin or extlupin than for those containing cpea or extpea while the NH 3-N contents were close. For extruded seeds, the contents for the various nitrogen fractions were lower than for the corresponding control seeds following a slower degradation in the rumen, which was con®rmed by the DegN parameters. For the clupin, part of the nitrogen was transiently solubilised as protein (42% N at 1 h and 33% N at 2 h) while for pea, whether extruded or not and for the extlupin, the solubilised N was mainly in the form of peptides, amino-acids and NH 3-N.