1. Department of Agricultural and Biosystems Engineering, Iowa State University , Ames, IA 50011 , USA
2. Department of Biosystems and Agricultural Engineering, University of Kentucky , Lexington, KY 40546 , USA
3. Department of Animal Sciences, University of Illinois Urbana-Champaign , Urbana, IL 61801 , USA
4. Department of Animal Science, North Carolina State University , Raleigh, NC 27695 , USA