1. Pfizer Animal Health, West Jefferson, NC 428694
2. Department of Veterinary and Biomedical Science, South Dakota State University, Brookings 57007
3. Texas AgriLife Extension Service, Texas A&M University, Dallas 75252
4. Pfizer Animal Health, Bakersfield, CA 93314
5. Department of Animal Sciences, Purdue University, West Lafayette, IN 47907