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Small intestinal digestibility of microbial and endogenous amino acids in dairy cows
Author(s) -
Larsen M.,
Madsen T. G.,
Weisbjerg M. R.,
Hvelplund T.,
Madsen J.
Publication year - 2001
Publication title -
journal of animal physiology and animal nutrition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.651
H-Index - 56
eISSN - 1439-0396
pISSN - 0931-2439
DOI - 10.1046/j.1439-0396.2001.00297.x
Subject(s) - latin square , amino acid , endogeny , chemistry , zoology , urea , food science , straw , digestion (alchemy) , dry matter , rumen , composition (language) , starch , biology , biochemistry , agronomy , chromatography , fermentation , linguistics , philosophy
The small intestinal digestibility of microbial amino acids and the apparent re‐absorption of endogenous amino acids were estimated in three ruminal, duodenal and ileal fistulated lactating dairy cows. The cows were assigned to a 3 × 3 Latin square and fed diets low in amino acids, composed of straw, starch, molasses and urea. The treatments were three straw to concentrate ratios. The digestibilities and re‐absorptions were estimated from duodenal and ileal flows of amino acids from feed, microbial and endogenous sources. The duodenal distribution of amino acids between different origins was determined by the difference method and by the amino acid profile method. The ileal distribution was estimated by a simple method where the feed fraction was estimated by the mobile bag method, the endogenous fraction as the water soluble fraction and the microbial fraction as the rest. In ileal samples, 8.0 ± 1.1, 52.2 ± 2.9 and 39.8 ± 2.6% of total amino acid nitrogen (AAN) were of feed, microbial and endogenous origin, respectively, compared with 5.1 ± 0.9, 61.6 ± 6.6 and 32.7 ± 6.9% in duodenal samples. The small intestinal digestibility of microbial AAN was estimated to be 75.1 ± 1.8% and the apparent re‐absorption of endogenous AAN to be 62.3 ± 11.1%.