Effect of the duration of feeding of a protein-free diet on endogenous ileal nitrogen and amino acid loss in the growing pig

The aim of the study was to determine whether endogenous nitrogen and amino acid excretions at the terminal ileum change over time in the growing pig fed a protein-free diet for 8 days. Seven entire male pigs with an overall mean live weight of 81.6 kg (SEM 3.3 kg) and surgically implanted post-valv e T caecum cannulas were fed a semi-synthetic casein-based diet for 8 days. Food was withheld from the pigs for 24 h, after which they were fed a prot ein-free diet for a further 8 days at a rate of 10% of metabolic body weigh t per day. Chromic oxide was included in the protein-free diet as an indige stible marker, Ileal digesta were collected continuously from 13:00 to 18:0 0 h on each day of the experimental period. Endogenous ileal nitrogen flows were determined for each pig each day the protein-free diet was given, and endogenous heal amino acid flows for the first and eighth days. There were no significant (P > 0.05) effects of the duration of feeding of the protei n-free diet on endogenous heal total nitrogen or amino acid flows, except f or the amino acids glycine and cysteine, the flows of which significantly d ecreased over the 8 day period (P < 0.01 and P < 0.05 for glycine and cyste ine respectively), from (mean +/- SEM) 1639 +/- 217 to 892 +/- 212 mu g g(- 1) dry matter intake (DMI) for glycine and from 173 +/- 13 to 127 +/- 19 mu g g(-1) DMI for cysteine. The relative contributions (moles of each amino acid as a proportion of total moles of amino acids) of threonine, glycine a nd cysteine decreased significantly (P < 0.05) and that of proline increase d significantly (P < 0.05) during the 8 days that the protein-free diet was fed to the pigs. (C) 2000 Society of Chemical Industry.