I want to thank the staff at Avesta European bison Park , Borås Zoo, Eriksberg Wildlife Sanctuary, Kolmården Wildlife Park , Lycksele Zoo, Skånes Djurpark and Skansen for giving me the opportunity to study their animals and their help to collect materials for the tests. I also want to thank my supervisor Mats Amundin for his help in this project. Special thanks to Erika Godoy for all her assistance during the project.