With the provisions of the present Decree, the administering to a farm animal, by any means, of substances having a thyrostatic action or substances having an oestrogenic, androgenic or gestagenic action, shall be prohibited. Slaughtering, processing and placing on the market of meat of farm animals to which the above-mentioned substances have been administered shall also be prohibited. However, administering such substances to farm animas may be approved for therapeutic use, synchronization of