1. U.S.
Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture, 1925 Linden Drive West, Madison, Wisconsin 53706, United States
2. Chemistry
and Biochemistry Laboratory, Food Production and Quality Division,
School of Agriculture, Policy and Development, University of Reading, P.O. Box 236, 1 Earley Gate, Reading RG6 6AT, United Kingdom