Special rules have also been set for feed materials which may act as direct or indirect protein sources and are called "bioproteins".

Bioproteins are for example extracted as by-products from fermentation processes. Council Directive 82/471/EEC gives rules for the authorisation of the use in feed of certain products, notably of bioproteins. The Annexes of this Directive give the positive list of the authorised bioproteins and have been amended by 9 Commission Directives. Certain groups of bioproteins must be scientifically evaluated on the basis of a dossier established following the guidelines fixed by Council Directive 83/228/EEC.

The authorisation of certain categories of bioproteins is subject to scientific advice of the Scientific Committee on Animal Nutrition and the Scientific Committee on Food.