title: Evaluation of the 15N-isotope dilution technique for determining the recovery of endogenous protein in ileal digestion of pigs: effect of dilution in the precursor pool for endogenous nitrogen secretion.
abstract: Three barrows, average initial BW of 35 kg, were fitted with a re-entrant cannula at the distal ileum and catheters in each of the external jugular veins. The barrows were fed twice daily a diet containing barley as the sole source of protein. A 1-d intravenous infusion of saline was followed by an 8-d continuous infusion of [15N]leucine at a rate of 30 mg/(kg BW x d). Blood samples, taken hourly for 9 d, were pooled over the 12-h period between feeding. Ileal digesta were collected hourly on d 3 and 8 of the [15N]leucine infusion and pooled over 12 and 24 h. Enrichments (atom percentage excess 15N) in nitrogen (N), leucine, isoleucine, valine and alanine were measured in the trichloroacetic acid (TCA)-soluble and -insoluble fractions of plasma and in ileal digesta. Although the enrichments in N were similar in all pools, enrichments in amino acids in the TCA-soluble fraction of plasma were at least twice that in the TCA-insoluble fraction and in ileal digesta. The estimated contributions of endogenous N and amino acids to total N and amino acids in ileal digesta were 82.3 +/- 9.38, 39.0 +/- 3.83, 43.8 +/- 6.50, 51.9 +/- 3.24, and 51.9 +/- 9.80 for N, leucine, isoleucine, valine and alanine, respectively. The results from this study indicate that enrichments in total N in the TCA-soluble fraction of plasma may not accurately reflect enrichments in endogenous N secreted into the intestinal lumen. This factor should be considered when using the 15N-isotope dilution technique to estimate the recovery of endogenous protein in ileal digesta of pigs fed protein-containing diets.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada.
authors.forename: K A
authors.initials: KA
authors.lastname: Lien
authors.forename: W C
authors.initials: WC
authors.lastname: Sauer
authors.forename: R
authors.initials: R
authors.lastname: Mosenthin
authors.forename: W B
authors.initials: WB
authors.lastname: Souffrant
authors.forename: M E
authors.initials: ME
authors.lastname: Dugan
mesh_terms: D000409:Alanine / Q000032:analysis; D000818:Animals; D002956:Citrulline / Q000032:analysis; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000032:analysis / Q000378:metabolism; D004063:Digestion / Q000502:physiology*; D005973:Glutamine / Q000032:analysis; D007082:Ileum / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D007201:Indicator Dilution Techniques / Q000662:veterinary*; D007262:Infusions, Intravenous; D007930:Leucine / Q000008:administration & dosage / Q000032:analysis; D008297:Male; D009584:Nitrogen / Q000032:analysis* / Q000097:blood / Q000378:metabolism; D009587:Nitrogen Isotopes; D011506:Proteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D013552:Swine / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014238:Trichloroacetic Acid; D014508:Urea / Q000032:analysis; D014633:Valine / Q000032:analysis
chemical_list: D004044:Dietary Proteins; D009587:Nitrogen Isotopes; D011506:Proteins; D005973:Glutamine; D002956:Citrulline; D014238:Trichloroacetic Acid; D014508:Urea; D007930:Leucine; D014633:Valine; D009584:Nitrogen; D000409:Alanine