COMPARISON OF THE ILEAL AND FECAL DIGESTIBILITY OF DIETARY AMINO-ACIDS IN ADULT HUMANS AND EVALUATION OF THE PIG AS A MODEL ANIMAL FOR DIGESTION STUDIES IN MAN

The aim of the study was to determine if there is a difference between ileal and faecal assays for determining amino acid and N digestibilit ies in adult human subjects. Comparison of true ileal amino acid and N digestibilities was also made between adult human subjects and growin g pigs to establish the usefulness of the pig as a model animal. Five subjects with established ileostomies and six subjects with intact lar ge bowels consumed a constant diet consisting of meat, vegetables, fru it, bread and dairy products for 7 d with collection of ileostomy cont ents or faeces respectively over the last 4 d. The study was repeated using 25 kg body weight ileostomized and intact pigs. Apparent amino a cid and N digestibility coefficients were determined. For human subjec ts the faecal digestibility values were significantly higher (P < 0.05 ) than the ileal values for Arg, Asp, Gly, Phe, Pro, Ser, Thr and Trp. The faecal digestibility of Met was significantly lower than the ilea l value. Determination of DNA, diaminopimelic acid (DAPA) and the dige stibilities of pectin, hemicellulose and cellulose in human subjects i ndicated that some microbial colonization had occurred at the terminal ileum after formation of an ileostomy; however, this was not as exten sive as in the large intestine. True deal amino acid and N digestibili ties were calculated after correcting for the endogenous contribution of amino acids at the terminal ileum determined using a protein-free d iet. There were no significant differences between adult human subject s and pigs for true ileal dietary amino acid digestibility except for Thr, Phe, Cys and Met. There were no significant differences between a dult humans and pigs for the heal digestibility of dry matter and the faecal digestibility of gross energy.