1. Department of Horse Breeding and Riding, Faculty of Animal Bioengineering, University of Warmia and Mazury, Oczapowskiego 5, 10-719 Olsztyn, Poland
2. Research Station of the Institute of Animal Reproduction and Food Research of PAS, Popielno 25, 12-220 Ruciane-Nida, Poland
3. Department of Animal Behaviour and Welfare, Institute of Genetics and Animal Biotechnology, Polish Academy of Sciences, 05-552 Jastrzębiec, Poland