1. USDA-ARS, Meat Animal Research Center, Spur 18D; Clay Center NE 68933
2. Palo Duro Research Facility, WTAMU Box 60938; West Texas A&M Univ.; Canyon TX 79016
3. USDA Agricultural Research Service, Agroecosystems Research Unit; 118 Keim Hall, UNL-East Campus Lincoln NE 68583
4. Department of Animal Science; University of Minnesota; 1364 Eckles Avenue St. Paul MN 55108