ARS | Publication request: Bacterial Population Shifts in the Rumen of Lactating Dairy Cows Within and Across Feeding Cycles

Submitted to: Journal Dairy Science Supplement
Publication Type: Abstract
Publication Acceptance Date: April 14, 2008
Publication Date: July 7, 2008
Citation: Welkie, D.M., Stevenson, D.M., Weimer, P.J. 2008. Bacterial population shifts in the rumen of lactating dairy cows within and across feeding cycles [abstract]. Journal of Dairy Science E-Supplement 1. 91:336.

Technical Abstract: While species composition of the ruminal microflora is thought to change during the feeding cycle due to variations in feed intake and ruminal environmental conditions, no studies have systematically characterized these purported population shifts. We used PCR amplification and automated ribosomal intergenic spacer analysis (ARISA) of bacterial DNA from bulk liquid and solid samples to profile changes in bacterial community composition (BCC) in two rumen-cannulated lactating cows over four successive 12-h feeding cycles. Cows were fed a TMR based on corn silage, alfalfa haylage, dry corn, and soybean meal. Ruminal samples were collected 2, 4, 6, 9, and 12 h post-feeding within each cycle. Cows did not differ in ruminal pH patterns and displayed only slight differences in VFA profiles, but displayed considerable differences in BCC. On average, samples contained 119 phylotypes (unique PCR amplicon lengths), of which 82 exceeded 1% of the peak height of the most abundant amplicon on capillary electrophoresis. Mean number of phylotypes did not differ (P>0.05) by sample type (solid or liquid), cycle number, or sampling time across cycles. Of 257 total phylotypes detected, only 19 were unique to one cow. Between cows, 29 phylotypes were detected only in the liquid phase, and 24 of these were common to both cows. By contrast, only 5 phylotypes were detected only in the solid phase, 2 of which were common to both cows. Principal component analysis revealed that bacterial population shifts within and across cycles were much greater in liquid samples than in solid samples. Bacterial populations generally returned to near their pre-feed compositions by the end of each cycle, suggesting that feeding resets BCC.