Endogenous ileal nitrogen and amino acid flows in the growing pig receiving a protein-free diet and diets containing enzymically hydrolysed casein orgraded levels of meat and bone meal

Endogenous ileal amino acid flows were determined in pigs fitted with simpl e T-cannulas using either the regression method (meat and bone meal (MBM) a s the protein source at five levels of inclusion) or following protein-free alimentation. Amino acid flows were compared with those determined by feed ing animals a diet the sole nitrogen source of which was enzyme-hydrolysed casein (EHC), followed by centrifugation and ultrafiltration of the ileal d igesta. The EHC was a mixture of free amino acids and oligopeptides (molecu lar weight <5000 Da). For the EHC treatment, the ileal digesta precipitate plus retentate was used to determine the endogenous flows. The ultrafiltrat ion step excludes unabsorbed dietary amino acids from the measure of endoge nous loss. Chromium III oxide was the reference marker in all diets. Estima tes of endogenous nitrogen and amino acid flows determined under protein-fr ee alimentation and the comparable flows determined using the regression me thod were similar. However, endogenous flows of amino acids for the EHC-fed pigs were generally significantly higher (P < 0.01) than values found for pigs on the protein-free diet and were higher than values obtained after ex trapolation for pigs given the MBM-based diets. Mean endogenous ileal nitro gen flow for the EHC-fed animals was 2526 (s.e. 33.9) compared with 1711 (s .e. 25.5) mg/kg dry-matter intake for pigs receiving the protein-free diet.