N. Gengler,* A. Tijani, and G.R. Wiggans *Passage des Déportés 2, B-5030 Gembloux, Belgium phone + 32 81 62 22 06, fax + 32 81 62 21 15 e-mail: [email protected] National Fund for Scientific Research, B-1000 Brussels, Belgium Animal Science Unit, Gembloux Agricultural University, B-5030 Gembloux, Belgium Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville...