1. Department of Animal Science, Purdue University, West Lafayette, IN 47907, USA
2. Department of Animal Science, University of Vermont, Burlington, VT 05405, USA
3. NASA/Ames Research Center, Moffett Field, CA 94035-1000, USA
4. Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, NC 27101, USA