1. USDA–ARS Conservation and Production Research Laboratory, Livestock Nutrient Management Unit, Bushland, TX
2. Department of Agriculture, West Texas A&M University, Canyon, TX
3. Texas A&M AgriLife Research, Amarillo, TX
4. Department of Animal Science and Food Technology, Texas Tech University, Lubbock, TX
5. ¶USDA–ARS Southern Plains Range Research Station, Rangeland and Pasture Research Unit, Woodward, OK