1 Departamento de Nutricion Animal, Facultad de Medicina Veterinaria y Zootecnia, Instituto Literario 100 Ote, Universidad Autonoma del Estado de Mexico, Toluca, Mexico.
2 Animal Production Group, Faculty of Environmental and Agricultural Sciences, University of Salamanca, Salamanca, Spain.
3 Department of Animal Sciences, School of Agriculture, Policy and Development, University of Reading, Reading, United Kingdom.