N-212. Effects of Sampling Time and Location of Rumen Contents on Rumen pH, Microbial Diversity and Metabolites
Background: The ruminal environment is a large and complex ecosystem housing a diverse population of microorganisms. Ruminal microbial fermentation of ingested feed contributes to fundamental components for cattle's daily nutrition uptake, production, and health maintenance. Microbial diversity profile is of research interests, but stratification within the rumen may prevent the collection of representative samples. As such, this study aims to investigate whether the differences in the detectable bacterial community were related sampling time and location in the rumen of dairy cows to using a culture-independent method. Methods: Three ruminally canulated cows fed a standard lactation diet were used in this study. Samples of rumen contents were collected from five different locations. In addition, samples were collected at three different time points corresponding to -3h, +3h and 9h relative to feeding. Total DNA was extracted from rumen contents and used as template to amplify partial bacterial 16S rRNA gene products with universal bacterial primers. The bacterial profiles of each rumen sample were analyzed using denaturing gradient gel electrophoresis (DGGE) and the obtained profiles were compared among locations and sampling times using Bionumerics software. Samples were also analyzed for pH and volatile fatty acid (VFA) and ammonia concentrations. Results: The PCR-DGGE analysis of detectable bacterial profiles showed no significant difference of bacterial diversity among five locations and three sampling time in each animal. Ruminal pH and VFA profile were affected by time of sampling (P < 0.001), but ammonia concentration was not. The location of sampling within the rumen did not affect the concentration of individual VFA and ammonia. Ruminal pH was affected by the location within the rumen (P < 0.05) Conclusion: Our results reveal that sampling location and time has no significant effect on detectable taxonomy of rumen microflora. The significant changes of VFA and pH at different time point suggest that numbers of cells of VFA producers may vary in response to the feeding.