1. Nutreco Research and Development, Boxmeer, the Netherlands
2. Wageningen Ur Livestock Research, Lelystad, the Netherlands
3. Animal Nutrition Group, Wageningen University, Wageningen, the Netherlands
4. Biometris, Wageningen, the Netherlands
5. IFIP–Institut du Porc, BP 35104, 35651 Le Rheu cedex, France