1. Department of Animal Sciences, University of Illinois, Urbana, IL
2. Departamento de Producción Animal, Facultad de Medicina Veterinaria y de Zootecnia, Universidad Nacional de Colombia, Bogotá, Colombia
3. Evonik Nutrition é Care GmbH, 63457 Hanau, Germany
4. Division of Nutritional Sciences, University of Illinois, Urbana, IL