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Title: Effect of Dietary Fiber on Endogenous Nitrogen Flows in Lactating Dairy Cows
Contributor(s): Ouellet, D R (author); Demers, M (author); Zuur, G (author); Lobley, G E (author); Seoane, J R (author); Nolan, John Vivian  (author)orcid ; Lapierre, H (author)
Publication Date: 2002
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Abstract: The effect of dietary fiber on endogenous N secretion was studied using a ¹⁵N isotope dilution technique in four fistulated Holstein cows. Two isonitrogenous diets differing only in fiber (NDF and ADF) content were used in a crossover design. One diet (HF) contained 37.4% NDF, while the other (LF) contained 23.3%. A new model was developed to estimate endogenous N secretions and losses for the preintestinal, intestinal, and the total sections of the gastrointestinal tract. Three precursor pools: TCA-soluble fraction of plasma, intestinal mucosa, and milk were compared. Although endogenous losses estimated with the model were numerically different for each precursor pool selected (TCA-soluble fraction > mucosa > milk), treatment effects were similar. As intestinal mucosa is probably closest to the precursor pool, these data are discussed. Non-urea N endogenous secretions contributed 13% of the duodenal N flow but were not affected by the fiber content of the diet. The nonurea N endogenous flow at the duodenum was comprised of approximately equal inputs from endogenous N direct, and that incorporated into the microbial biomass. Total endogenous N flows at the duodenum exceeded, by nearly twofold, estimated inputs of urea-N to microbial biomass. Metabolic fecal output averaged 17% of fecal N and was not affected by level of dietary fiber, but net losses from secretions occurring in the small intestine were higher with the low fiber diet. Overall, endogenous N secretions represented 30% of total digestive tract protein synthesis.
Publication Type: Journal Article
Source of Publication: Journal of Dairy Science, 85(11), p. 3013-3025
Publisher: Elsevier Inc
Place of Publication: United States of America
ISSN: 1525-3198
Field of Research (FOR): 070204 Animal Nutrition
Socio-Economic Outcome Codes: 830302 Dairy Cattle
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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