RumenMicrobiotaMetagenomeGastrointestinal TractBacteriaBiodiversityRNA, Ribosomal, 16SPhylogenyGenetic VariationIntestinesFecesBiotaDenaturing Gradient Gel ElectrophoresisSequence Analysis, DNAPrebioticsBifidobacteriumFermentationFatty Acids, VolatileGerm-Free LifeProbioticsCiliophoraAnimal FeedDNA, BacterialBacteroidesDNA, RibosomalBacteroidetesCattleMolecular Sequence DataDysbiosisSheepReticulumRuminococcusEcosystem