A Casein Hydrolysate Does Not Enhance Ileal Endogenous Protein Flows Compared With the Parent Intact Casein When Fed to Growing Pigs

Background: The form of dietary nitrogen (free peptides or intact proteins) may influence theamount of endogenous amino acids found at the terminal ileum of the pig, and it has beenspeculated that hydrolyzed dietary protein may lead to increased endogenous amino acids.Objective: To compare the effect of dietary free peptides on ileal endogenous nitrogen andamino acid flows [ileal endogenous nitrogen flow (ENFL), ileal endogenous amino acid flow(EAAFL)] with that of peptides released naturally from dietary protein during digestion, from thesame intact parent protein source.Methods: Six pigs (mean body weight: 34 kg) were equipped with a postvalve T-caecum cannula.Semisynthetic test diets contained the same 15N-labeled intact casein (C) or hydrolyzed casein(HC). Pigs received the test diets every sixth day and the corresponding unlabeled diets in theintervening 5-d periods. Digesta were pooled from 4 to 10 h postprandially. EAAFL and ENFL,calculated with reference to the dietary marker titanium dioxide, were determined by isotopedilution for C and HC.Results: Ileal EAAFL and ENFL (mean flows n = 5 of 1828 and 1912 μg/g of dry matter intake fordiets HC and C, respectively) did not differ (P > 0.05) between pigs fed HC and C. Centrifugationand ultrafiltration of the HC digesta allowed an estimation of label recycling into gut endogenousproteins. Some 20% of ileal endogenous protein (diet HC, ultrafiltered digesta) was 15N-labeleddue to tracer recycling.Conclusions: The administration of a casein hydrolysate had no effect on ileal endogenous proteinflows compared with C. There was no evidence of enhanced ileal endogenous protein losses withthe HC diet.