Paragraph 6
No material shall contain any added vitamin, pro-vitamin or substance having a similar effect except that—
any material for any animal of a kind specified in column 3 of Chapter A of Part V may contain added vitamin D2; or D3; (but not both) in proportions which, taking account of any such vitamin which is naturally present, do not exceed the maximum content specified in column 4 of the said Chapter in relation to the kinds of animal specified in column 3 thereof, and provided that the conditions (if any) specified in column 5 of that Part are complied with;
any material for any animal of a kind specified in column 3 of Chapter B of Part V may contain any vitamin, (other than vitamins A, D2; or D3;) or any pro-vitamin or chemically well defined substance having a similar effect in proportions which, taking into account any such substance which is naturally present, do not exceed the maximum content (if any) specified in column 4 in relation to the kinds of animal specified in column 3 thereof.