Alterations in the rumen liquid-, particle- and epithelium-associated microbiota of dairy cows during the transition from a silage- and concentrate-based ration to pasture in spring

In spring dairy cows are often gradually transitioned from a silage- and concentrate-based ration (total mixed ration, TMR) to pasture. Rumen microbiota adaptability is a key feature of ruminant survival strategy. However, only little is known on the temporal and spatial microbial alterations involved. This study aims to investigate how the rumen liquid (LAAB), particle (PAAB) and epithelium (EAAB) associated archaea and bacteria are influenced by this nutritional change. A 10-wk trial (wk 1-10) was performed, including 10 rumen-fistulated dairy cows, divided into a pasture- and a confinement group (PG and CG). The CG stayed on a TMR-based ration, while the PG was gradually transitioned from TMR to pasture (wk 1: TMR-only, wk 2: 3 h/day on pasture, wk 3 & 4: 12 h/day on pasture, wk 5-10: pasture-only). In wk 1, wk 5 and wk 10 samples of solid and liquid rumen contents, and papillae biopsies were collected. The DNA was isolated, and 16S rRNA gene amplicon sequencing analysis (Illumina MiSeq) was performed. The corresponding manuscript is currently under revision: The adaptation of the rumen liquid-, particle- and epithelium-associated microbiota of dairy cows during the transition from a silage- and concentrate-based ration to pasture in spring.Melanie Schären1, Kerstin Kiri2, Susanne Riede2, Mark Gardener3, Ulrich Meyer1*, Jürgen Hummel4, Tim Urich5, Gerhard Breves2, and Sven Dänicke1 1Institute of Animal Nutrition, Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Brunswick, Germany2Department of Physiology, University of Veterinary Medicine Hannover, Hannover, Germany3Environment, Earth & Ecosystems, The Open University, Milton Keynes, United Kingdom4Ruminant Nutrition, Department of Animal Sciences, Faculty of Agricultural Sciences, Georg-August University Göttingen, Göttingen, Germany5Institute of Microbiology, University of Greifswald, Greifswald, Germany* Correspondence: Dr. Ulrich [e-mail]