We understand that it is totally forbidden within the same animal species and not only for the protein, but for all slaughterhouse by-products. Therefore, sebum can not be used in ruminants, lard can not be used in pigs, etc. According to the European Commission

http://europa.eu/rapid/press-release_MEMO-04-107_en.pdf

MEMO / 04/107
Brussels, 6 May 2004
QUESTIONS And Answers on animal by-products

Intra-species recycling (cannibalism) ban The regulation extends the current ruminant intra-species recycling (cannibalism) ban to other species. Porcine animal by-products can not be fed to pigs and animal poultry by-products. However, derogation is provable for the case of fish and fur animals subject to strict controls by the competent authority.

«The regulation extends to other species the prohibition, already applicable to ruminants, of the recycling (of by-products) within the same species ...»

More clear water!