Until well into the beginning of the 20th century, fonds were usually made by boiling different meats and fowl together. But today, the flavor of a fonds generally corresponds to the ingredient it is accompanying. For example, veal fonds would be used for veal and beef preparations. (Note that mature beef is not used for beef preparations because as an adult animal, its flavor is considered too strong for use in fonds. This is true of the mature pig also.)
The color of the fonds should also correspond with certain preparations, so if desired a fish fumet could be used with chicken, such as for a poulet marengo, and fond d’agneau is sometimes used with similar meat types in order to highlight the flavor of certain recipes.