1. USDA‐ARS, Poultry Production and Products Safety ResearchO‐303, Poultry Science CenterFayettevilleAR72701
2. Oklahoma State Univ.Dep. of Plant and Soil ScienceStillwaterOK74078
3. Texas Tech Univ.Dep. of Plant and Soil ScienceLubbockTX79409
4. Univ. of ArkansasDep. of Crop, Soil, and Environmental SciencesFayettevilleAR72701
5. Univ. of ArkansasDep. of Agricultural Economics and AgribusinessFayettevilleAR72701