GUT ENDOGENOUS NITROGEN AND AMINO-ACID EXCRETIONS IN ADULT DOMESTIC CATS FED A PROTEIN-FREE DIET OR AN ENZYMATICALLY HYDROLYZED CASEIN-BASED DIET

Ileal and fecal gut endogenous nitrogen and amino acid excretions in a dult domestic cats were determined. Ileal digesta were collected (10 c m of terminal ileum) from the cats fed either a protein-free diet or a n enzymatically hydrolyzed casein-based diet (free amino acids and pep tides <10,000 Da) for 1 wk. Chromic oxide was included in each diet as an indigestible marker. The relative contribution of the hindgut to t otal endogenous gut excretion was investigated in a separate study by feeding cats a protein-free diet with or without added antibiotics for 10 d. Endogenous ileal nitrogen and amino acid nitrogen excretions of (mean +/- SEM) 2.4 +/- 0.27 and 1.9 +/- 0.13 mg/g food dry matter int ake, respectively, were found for the cats fed the protein-free diet, whereas higher excretions of 3.6 +/- 0.73 (P = 0.12) and 3.6 +/- 0.76 (P = 0.03) mg/g food dry matter intake were obtained in cats fed the e nzymatically hydrolyzed casein. Significantly (P < 0.05) higher endoge nous ileal amino acid excretions, for the enzymatically hydrolyzed cas ein-fed cats compared with those fed the protein-free diet, were found for methionine, aspartic acid, serine, glutamic acid, proline, valine and isoleucine, with the differences in excretions of glycine, alanin e, leucine and histidine being significant at the 6% level. Most of th e endogenous fecal amino acid excretions were unaffected by the inclus ion of the antibiotics in the protein-free diet, although bacterial nu mbers were significantly lower (69%). Antibiotics addition led to sign ificantly higher fecal endogenous excretions of nitrogen, taurine, thr eonine, serine and histidine but significantly lower excretions of met hionine and lysine. Cats, like other simple-stomached mammals, excrete higher amounts of endogenous amino acids at the terminal ileum when t he diet contains peptides.