1. Chemistry
and Biochemistry Laboratory, School of Agriculture, Policy and Development, University of Reading, 1 Early Gate, P.O. Box 236, Reading RG6 6AT, United Kingdom
2. Agroscope, Institute
for Livestock Sciences, Route de la
Tioleyre 4, 1725 Posieux, Switzerland
3. INRA, UMR 1213 Herbivores, F-63122 Saint-Genès-Champanelle, France