1. Department of Animal Science, University of California, Holtville, CA, USA
2. Department of Nutrition and Biotechnology of Ruminants, Instituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexicali, México.
3. Department of Animal Science, University of California, Davis, CA, USA
4. Department of Animal Nutrition, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Tamaulipas, Cd. Victoria, México