volatile fatty acid nonhuman 4 Fatty Acids, Volatile 3 chemistry 3 metabolism 3 waste water management 3 Anaerobic digestion 2 Animal Feed 2 Animals 2 Article 2 Chromatography, High Pressure Liquid 2 Diet 2 Fagus 2 Fagus sylvatica L 2 Fermentation 2 Flavonoids 2 Plant Leaves 2 Rumen 2 Ruminants 2 UHPLC-ESI-QqTOF analysis 2 acetic acid 2 animal 2 animal food 2 article 2 beech 2 biogas 2 controlled study 2 diet 2 fermentation 2 flavonoid 2