1. Animal Husbandry and Animal Ecology, Institute of Agricultural and Nutritional Sciences, Martin-Luther University of Halle-Wittenberg, 06120 Halle, Germany
2. Centre for Proper Housing of Ruminants and Pigs, FSVO, Agroscope Tänikon, 8356 Ettenhausen, Switzerland
3. School of Psychology and Life Sciences, Canterbury Christ Church University, Canterbury CT1 1QU, UK
4. Biological and Experimental Psychology, School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK
5. Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong SAR, People's Republic of China
6. Institute of Behavioural Physiology, Leibniz Institute for Farm Animal Biology, 18196 Dummerstorf, Germany