ARS | Publication request: EVALUATION OF RUMINAL MICROBIAL POPULATION CHANGES DURING ACIDOSIS USING RIBOSOMAL RNA-TARGETED DNA PROBES

Submitted to: American Dairy Science Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: July 17, 1996
Publication Date: N/A

Technical Abstract: The effects of acidosis on key ruminal microbial populations were evaluated. Four lactating cows were fed a basal diet (60% alfalfa hay and 40% concentrate) for 24 days. After a 12 hour fast, cows were fed an acidotic diet (20% alfalfa hay and 80% concentrate) for 24 hours and ruminal samples taken through 72 hours. Nucleic acids were extracted from samples and hybridized with radiolabelled small subunit (SSU) rRNA-targeted DNA probes. Abundance of microbial groups are presented as a percentage of total SSU rRNA and are averages of four cows. At 10 hours, pH reached a minimum of 5.44. Correlation with pH was positive for the relative abundance of Eucarya (r=.53, P<.01) and Fibrobacter (r=.60, P<.01) but negative for Bacteria (r=.43, P<.01) and Ruminococcus albus (r=.24, P=.04). Relative abundance of Streptococcus bovis reached a maximum of 5.8% at 20 hours when pH was 5.70. Microbial populations were affected by acidosis perturbation in the rumen but recovered as pH increased.