Major supermarkets throughout the UK acknowledge thatthe meat, fish, eggs and dairy products they sell may be derived from animals supplied with genetically modified feed, which is not required to be declared on labeling.

http://www.telegraph.co.uk/foodanddrink/7852762/Supermarkets-selling-meat-from-animals-fed-GM-crops.html
http://info-wars.org/2010/06/26/uk-supermarkets-selling-meat-from-animals-fed-gm-crops/