Changes to Council Directive 74/63/EEC of 17 December 1973 on the fixing of maximum permitted levels for undesirable substances and products in feedingstuffs
EU Directive 1974/63
Made by Council Directive 91/132/EEC of 4 March 1991 amending Directive 74/63/EEC on undesirable substances and products in animal nutrition
From legislation.gov.uk's record of changes, the official one: see it there.