1. Department of Animal Sciences, University of Missouri, Columbia, MO 65211
2. Department of Animal Production, Nanjing Agricultural University, Nanjing, People's Republic of China
3. U.S. Department of Agriculture, Agricultural Research Service, Animal Physiology Research Unit, University of Missouri, Columbia, MO 65211
4. Division of Animal Sciences, Monsanto Company, Chesterfield, MO 63198