Bile acids can be divided into free bile acid and conjugated bile acid. The former includes cholic acid (CA), chenodeoxycholic acid (CCA), deoxycholic acid (DCA) and (LCA), etc .; the latter is the product of free bile acids combined with glycine or taurine. At physiological pH, the taurine conjugates are mostly present in the ionic state, while the glycine conjugates are treated with ions and molecules two forms coexist. From the source can be divided into primary bile acid (primary bile acid) and secondary bile acid (secondary bile acid), liver cells directly to cholesterol as raw material synthesis of bile acid for the primary bile acid; primary bile acid in the intestinal tract by bacteria. 
In addition, the different animal bile acid type and quantity are not the same, such as dairy cow bile acid main component of cholic acid and deoxycholic acid; chicken body bile acid main component of ghenodeoxycholic acid, cholic acid, which deoxycholic acid accounting for 80% of total bile acid, cholic acid accounted for 17% of total bile acid; pig bile acid in the main components of α-hyodeoxycholic acid, chenodeoxycholic acid, bilirubin, which α-hyodeoxycholic acid accounted for 40% of the total bile acid, chenodeoxycholic acid accounted for 6.8% of the total bile acid; shrimp, crab and other crustaceans are invertebrates, no bile secretion, no bile acid.