Opinion of the Economic and Social Committee on the proposals for: a Council Directive concerning products used in animal nutrition, a third Council Directive amending Directive 70/524/EEC concerning additives in feedingstuffs, a Council Directive amending Directive 74/63/EEC fixing maximum permitted levels for undesirable substances and products in feedingstuffs and amending Directive 70/373/EEC introducing Community methods of sampling and analysis for the official control of feedingstuffs