The enzyme hydrolysed protein method for the determination of endogenous ileal nitrogen and amino acid flows—a modification

Abstract

The aim of the work was to examine the effect of using an ultrafiltration device with a molecular weight (MW) cut-off of 3000 Da on endogenous ileal amino acid flows determined using the enzyme hydrolysed protein method, as compared with those determined using a MW cut-off of 10,000 Da. Endogenous ileal nitrogen and amino acid flows determined using the enzyme hydrolysed protein method are normally determined using a MW cut-off of 10,000 Da for ultrafiltration. Digesta were sampled from the terminal ileum of male rats ( n=24) that had received a diet containing enzyme hydrolysed casein (EHC) at an inclusion level of 100 g/kg, for 8 days. The digesta samples were divided into six groups, each containing the digesta from four rats. Endogenous ileal nitrogen and amino acid flows were determined on each pool of digesta using the enzyme hydrolysed protein method with ultrafiltration using MW cut-offs of 10,000 and 3000 Da. The endogenous ileal nitrogen and amino acid flows determined using a MW cut-off of 3000 Da for ultrafiltration were greater than those determined using a MW cut-off of 10,000 Da. The percentage difference in endogenous flow between the results obtained following ultrafiltration at 10,000 Da and those at 3000 Da was 17% for nitrogen and ranged from 1.7% for arginine and phenylalanine to 26% for serine, with a mean difference of 12% for the amino acids. When determining endogenous ileal nitrogen and amino acid flows using the enzyme hydrolysed protein method, it is recommended that digesta be ultrafiltered using a MW cut-off of 3000 Da, but the MW cut-off for ultrafiltration must be related to the size of peptides present in the enzyme hydrolysed protein.