Effectiveness of an ultrafiltration device for use with the enzyme‐hydrolysed protein method for determining endogenous ileal nitrogen and amino acid excretion in the pig

Abstract

AbstractThe aim of the work was to perform an in vitro study to determine the effectiveness of Centriprep‐10 concentrator devices for use with the enzyme‐hydrolysed protein method for the determination of endogenous ileal nitrogen and amino acid flows. Different amounts of enzyme‐hydrolysed casein (EHC) were added to tubes containing digesta collected from pigs that had received a protein‐free diet for 5–8 days. The samples were centrifuged and then ultrafiltered using Centriprep‐10 concentrators. The precipitate from the centrifugation step was added to the retentate from the ultrafiltration, and this material was analysed for nitrogen and amino acids. The ultrafiltrates were also analysed for nitrogen. The amount of nitrogen that was deemed to have originated from the EHC and remained in the precipitate plus retentate fraction of digesta after processing, expressed as a percentage of the total amount of nitrogen added to the tubes as EHC, ranged from 1.0 to 5.0%. The overall mean amounts of amino acid in the precipitate plus retentate fractions originating from the EHC, expressed as a percentage of the amino acids added to the tubes as EHC, ranged from 2.4 to 5.8%. The results demonstrate that with Centriprep‐10 concentrators there is a less than complete separation of nitrogen and amino acids originating from EHC from endogenous material in digesta, but for most amino acids this is unlikely to be due to binding of the amino acids to digesta. The incomplete separation of EHC from the endogenous fraction of digesta by Centriprep‐10 concentrators may lead to a small overestimation (approximately 2%) of endogenous ileal nitrogen and amino acid flows.© 2001 Society of Chemical Industry