1. a Animal and Microbial Biology Unit, Gembloux Agricultural University , Gembloux , Belgium
2. b Animal Science Unit, Gembloux Agricultural University , Gembloux , Belgium
3. c Center of Numerical Molecular Biophysics, Gembloux Agricultural University , Gembloux , Belgium
4. d UR339 Laboratoire de Génétique Biochimique et Cytogénétique, INRA-CRJ , Jouy-en-Josas , France
5. e National Fund for Scientific Research , Brussels , Belgium
6. f Veterinary Physiology and Nutrition Unit, University of Udine , Udine , Italy