1. Animal Science, 109 Kildee Hall, Iowa State University, Ames 50011
2. United States Department of Agriculture, Agricultural Research Service, United States Meat Animal Research Center, Clay Center, NE 68933
3. Production Research, Murphy Brown, LLC, 4134 Hwy 117 S, Rose Hill, NC 28458
4. Department of Swine Reproductive Physiology, University of Alberta, Edmonton, AB T6G 2P5, Canada