It is common in UK supermarkets to see packs of beef labelled 'grass-fed'. What is the legal significance, if any, of this term? If there is, a reference to an official source would be appreciated.
I have seen apparently conflicting statements on different websites. Some (eg here and here) state that there is no legal definition of 'grass fed' in the UK. Others (eg here and here refer to a definition of 'grass-fed' as fed at least 51% on grass, or equivalently not more than 49% on other foods. This site, confusingly (see under the heading 'Is all grassfed the same?'), seems to make both claims.
A clarification. It seems to be generally recognised in this context that 'grass' includes grass-based feed in the form of hay, silage, etc. The distinction at issue here is between grass and grass-based feed on the one hand and concentrated feeds such as those including wheat, corn (maize) and fats on the other.