Abstract
The effects of steam-flaked corn bulk density during grain adaptation phase on ruminal microbiome were evaluated. Crossbred-Angus ruminally cannulated steers (n = 6; BW = 405 ± 42 kg) were assigned to a randomized complete block design (block = body weight) to 1 of 2 grain adaptation strategies: 1) steam-flaked corn (SFC) bulk density of 335 g/L; and 2) 412 g/L. Steers were ad libitum fed, individually, during 6-7d phases, consisting of: HAY, followed by the STEP-UP1 through STEP-UP4, diets, respectively, in which roughage was gradually replaced with grain until FINISHER diet was fed. Respective SFC bulk densities were fed throughout STEP-UP diets, while the FINISHER diet consisted of 335 g/L strategy only for both groups. Ruminal fluid samples (100 mL) were collected on d-5 of each step, at 6h post-feeding for DNA extraction. Microbiome data were sequenced by Illumnia® NovaSeq™ 6000 (16S rRNA). The SFC bulk density did not affect (P > 0.50) the relative abundance (RA) for any taxonomy classification. Regardless of SFC bulk density, inclusion of grain throughout adaptation phases affected domain (P ≤ 0.03) when initial phases were compared to FINISHER. Phylum RA were affected (P ≤ 0.05) for Actinobacteria (27%), Bacteroidetes (11%), and Euryarchaeota (2%). Within Class RA were affected (P ≤ 0.04) for Clostridia (46%), Actinobacteria (27%), and Bacilli (5%). Order effects on RA were observed (P ≤ 0.04) for Clostridiales (45%), Coriobacteriales (25%), and Lactobacillales (4%). Within Family RA was affected (P ≤ 0.03) for Coriobacteriaceae (25%), Lachnospiraceae (27%), Ruminococcaceae (6%), and Lactobacillaceae (4%), while a tendency (P = 0.09) was observed for Veillonellaceae (1%). In Genus, RA was affected (P ≤ 0.01) for Olsenela (22%), Pediococcus (3%), and Butyrivibrio (3%). As steers advance through subsequent grain adaptation phases until the FINISHER, more meaningful ruminal microbiome changes are observed than SFC density change.
Metatranscriptomics of the Hu sheep rumen microbiome reveals novel cellulases
