Bile salts of germ-free domestic fowl and pigs.

1. The bile of germ-free domestic fowl contains taurine conjugates of 3alpha,7alpha-dihydroxy-5beta-cholan-24-oic acid (chenodeoxycholic acid), 3alpha,7alpha,12alpha-trihydroxy-5beta-cholan-24-oic acid (cholic acid) and its 5alpha-epimer (allocholic acid): that of germ-free pigs contains glycine and taurine conjugates of chenodeoxycholic acid, 3alpha,6alpha-dihydroxy-5beta-cholan-24-oic acid (hyodeoxycholic acid), 3alpha,6alpha,7alpha-trihydroxy-5beta-cholan-24-oic acid (hyocholic acid) and (probably) cholic acid. Keto acids were not found. 2. Allocholic acid and hyodeoxycholic acid are thus proved to be primary bile acids in intact animals. 3. The evolutionary and biochemical implications of these findings are briefly considered.