Nitrogen transactions along the gastrointestinal tract of cattle: A meta-analytical approach.
J Anim Sci
; 86(3): 660-79, 2008 Mar.
Article
en En
| MEDLINE
| ID: mdl-18073282
ABSTRACT
In ruminant animals, endogenous N (EN) secretions contribute to meeting the N requirement of the ruminal microflora. The EN also constitutes a sizable portion of the duodenal N flow, which might be available to the host animal. Most measures of EN have been accomplished with highly invasive techniques or unusual semisynthetic diets. By utilizing a statistical approach and data obtained from studies reporting duodenal, ileal, and fecal N flows in cattle, the EN losses and true digestibility of N were estimated for different segments of the gastrointestinal tract of cattle. A simulation for a reference diet (24.2 g of N/kg of OM, 32% NDF and carbohydrates of medium fermentation rate) consumed at 2% of BW daily estimated that the minimal contribution of EN to the N available in the rumen was 39%. The free EN represented 13% of the duodenal N flow, and when bacterial N of EN origin was considered, EN contributed 35% of the total N flow. The minimal entry of EN into various segments of the gastrointestinal tract was also estimated as foregut, 10.54; small intestine, 3.10; and hindgut, 5.0 g/kg of OMI. Rumen dietary N degradability was 0.68, and true N digestibilities in the small intestine and hindgut were 0.75 and 0.49, respectively. A better understanding of the factors involved in EN losses will allow for a more accurate estimation of both N supply and N requirements. This will translate into improved accuracy of diet formulation and less N excreted into the environment.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Bovinos
/
Tracto Gastrointestinal
/
Digestión
/
Nitrógeno
Tipo de estudio:
Diagnostic_studies
/
Prognostic_studies
/
Systematic_reviews
Límite:
Animals
Idioma:
En
Revista:
J Anim Sci
Año:
2008
Tipo del documento:
Article
País de afiliación:
Estados Unidos