1. Animal Welfare & Behaviour Group, School of Veterinary Sciences, Bristol University, Langford House, Langford, Bristol, BS40 5DU, United Kingdom
2. Louis Bolk Institute, Hoofdstraat 24, 3972 LA Driebergen, The Netherlands
3. Adaptation Physiology Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands
4. Livestock Research, Wageningen UR, PO Box 65, 8200 AB, Lelystad, The Netherlands
5. Animal Breeding and Genomics Centre, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands
6. Behavioural Ecology Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands