Evaluation of the 15N-isotope dilution technique for determining the recovery of endogenous protein in ileal digesta of pigs: effect of the pattern of blood sampling, precursor pools, and isotope dilution technique.

Abstract

The 15N-enrichments (atom percentage excess) were determined in the plasma free amino acids of blood samples taken at the time of feeding and in samples taken hourly and pooled over 12 h, as well as in ileal digesta, crude mucin, and bacteria collected at the distal ileum of pigs fed barley while continuously administered [15N]leucine intravenously. The branched-chain amino acids were the only indispensable amino acids to exhibit incorporation of 15N (P < .05). All dispensable amino acids exhibited some incorporation. Enrichments in free leucine and alanine were higher (P < .02) in blood samples taken at the time of feeding, compared to those in pooled blood samples, resulting in an underestimation of the endogenous ileal recoveries of these amino acids. Enrichments in amino acids in crude mucin were usually similar to those in pooled plasma samples, providing some support for the use of plasma free amino acids to estimate enrichments in endogenous amino acids in ileal digesta. Enrichments in bacteria were not different (P > .05) from those in ileal digesta. The recoveries of endogenous amino acids in ileal digesta determined with the [15N]leucine and 15N-amino acid dilution techniques demonstrate the overestimation of these criteria with the 15N-isotope dilution technique, applied in its current form, and suggest that modifications in the composition of endogenous protein can occur when pigs are fed protein-containing diets. These study supports the use of 15N-isotope dilution techniques, with modifications, for determining the recovery of endogenous protein in ileal digesta of pigs fed protein-containing diets.

Determination of endogenous nitrogen associated with bacteria in ileal digesta of pigs receiving cereal-based diets with or without fish meal and various fibre supplements by using a simple ¹⁵N-dilution technique

“…It is concluded that steady state conditions were obtained after three days following the last administration of 15 NH 4 C1 in pigs given both the diets with and without fish meal. A similar atom % 15 N' in bacterial and total N of ileal digesta was also reported by Lien et al (1997b). This means that bacterial N contains the same proportion of 15 N-labelled endogenous N as the total N of ileal digesta, which is also presented in Tables 3 and 4.…”

Refined methodology to purify mucins from pig colonic mucosa

“…The proportion of PTS in crude mucin purified using the refined method is within the wide range of values (32-43%; Lien et al, 1997;Fogg et al, 1996) reported for pig intestinal mucins, purified using different techniques (ethanol precipitation, CsCl density gradient centrifugation). The latter method has been commonly used in the past years to purify mucins of acceptable purity.…”

Effect of dietary nutrients on ileal endogenous losses of threonine, cysteine, methionine, lysine, leucine and protein in broiler chicks

“…The EFR is defined as the labeled AA who passes from plasma to ileal digesta, assuming that enrichment of AA in plasma are similar to enrichment of endogenous AA in ileal digesta as demonstrated by Lien et al (1997b). The following formula was used according to Yin et al (2000):…”

“…Several studies in pigs (Lien et al, 1997b;Leterme et al, 1998;Hess et al, 2000) and a few in chickens (Danicke et al, 2000;Xu et al, 2011) have tried to measure the endogenous AA losses using practical diets; however, the variations of labeled sources, days of feeding, route of administration have made it difficult to define an accurate and reliable model. Steendam et al (2004) demonstrated that route of tracer administration (oral or intravenous infusion) did not affect the ileal endogenous nitrogen recovery.…”