1. Plant Science Department, Pennsylvania State University, University Park 16802
2. Animal Science Department, Pennsylvania State University, University Park 16802
3. USDA-Agricultural Research Service, Pasture Systems and Watershed Management Research Unit, University Park, PA 16802
4. Department of Animal Science, Pennsylvania State University, University Park 16802
5. DairyNZ, Hamilton 3240, New Zeal
6. Agriculture and Consumer protection Department, Food and Agriculture Organization of the United Nations, 00153 Rome, Italy
7. Wageningen University, 6700 AH Wageningen, The Netherlands