title: Ruminal degradability and intestinal digestibility of individual amino acids in mixed diets with different crude protein levels measured by the modified in vitro three-step and mobile nylon bag technique.
abstract: The ruminal degradability and intestinal digestibility of dry matter (DM), crude protein (CP) and amino acids (AA) in three total mixed rations with different CP levels were estimated using the modified in vitro three-step procedure (TSP) and mobile nylon bag (MNB) technique on growing lambs. The ruminal effective degradability of DM and CP did not respond with increasing dietary CP level. However, the intestinal digestibility of DM was significantly increased with increasing dietary CP level estimated by TSP (P < 0.05) or MNB method (P < 0.01). Intestinal digestibility coefficients of CP determined by TSP were lower than those of the MNB method. Histidine was extensively degraded by rumen micro-organisms, while tyrosine was the most anti-degradable AA among the samples. The ruminal AA degradability exhibited no significant differences except for threonine, tryptophan, alanine, aspartic acid and proline for the three diets. Similarly, only a few AAs (i.e. histidine, methionine, tryptophan, aspartic acid and cysteine in TSP; histidine, tryptophan, aspartic acid and serine in MNB) had significant differences in their intestinal digestibility; in addition, values of MNB were lower than that of the TSP method, indicating that intestinal digestibility of DM seems to be overestimated in TSP, while that of CP might be overestimated in the MNB method.
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.forename: Bowen
authors.initials: B
authors.lastname: Zhang
authors.forename: Bo
authors.initials: B
authors.lastname: Lv
authors.affiliation: College of Animal Science and Technology, Shihezi University, Shihezi City, China.
authors.forename: Chenli
authors.initials: C
authors.lastname: Liu
authors.forename: Daofu
authors.initials: D
authors.lastname: Chen
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D004032:Diet / Q000662:veterinary*; D004044:Dietary Proteins / Q000378:metabolism*; D004063:Digestion / Q000502:physiology*; D066298:In Vitro Techniques / Q000379:methods*; D009757:Nylons; D059748:Proteolysis; D012417:Rumen / Q000502:physiology*; D012756:Sheep
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D009757:Nylons
keywords: amino acid profile; in vitro three-step procedure; intestinal digestibility; mobile nylon bag technique; ruminal degradation