1. Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK 74078.
2. Department of Animal Sciences, University of Missouri, Columbia, MO 65211.
3. Department of Agricultural and Biological Engineering, University of Illinois, Urbana, IL 61801.
4. Department of Veterinary Pathobiology, University of Illinois, Urbana, IL 61801.
5. Department of Veterinary Biosciences, University of Illinois, Urbana, IL 61801.
6. Corresponding author. Phone: 217-265-0697. Fax: 217-244-0323. E-mail: krausch@uiuc.edu