The present invention refers to an animal feed additive effective as broad-spectrum preservative, said feed additive comprises as active ingredients propionic acid, glyceryl propionates, hexanoic acid and optionally minor amounts of an alkali metal salt and/or a C7-C12 fatty acid. The present invention also refers to the use of said animal feed additive as a mould and/or yeast inhibitor and to the use of said animal feed additive as an inhibitor of aerobic bacteria. In a further aspect, the present invention refers to the use of said animal feed additive to protect an animal feed from aerobic deterioration.