This "Book of Abstracts" is the main publication of the 56th Annual Meeting of the European Association for Animal Production (EAAP) held in Uppsala, Sweden, on 5-8 June 2005. It contains abstracts of the invited papers and contributed presentations. The meeting addressed subjects relating to science and innovation, but in Uppsala the main theme is "Impact and Challenges of a widening Europe for Animal Production and Research". Also, important problems were discussed during the sessions of EAAP"s nine Commissions: Animal Genetics, Animal Nutrition, Animal Management and Health, Animal Physiology, Cattle Production, Sheep and Goat Production, Pig Production, Horse Production and Livestock Farming Systems. In addition joint sessions on topics interesting several disciplines and species were included in the programme. A total of 2005 authors (773 abstracts) contributed to this publication.