Ruminal bacterial community displays substantial host specificity
We are walking ecosystems, each of us are home to thousands of different species on and inside of us. The crosstalk between the host and microorganisms is intriguing. Cows are amazing creatures: they rely on gut microbes to digest fibers or feedstuffs that are indigestible by humans to support metabolic rates that exceed those of marathon runners. If microbes are important to humans, they are probably even more so to dairy cows. We have just begun to scratch the surface of exploring the relationship between host and microbes in ruminants, and some recent data suggest that ruminal bacterial community displays substantial host specificity.
The research team at USDA Dairy Forage Research Center (Weimer et al. 93:5902-5912. 2010. J. Dairy Sci.) selected a pair of cows with very different bacterial community composition and exchanged >95% of ruminal contents one time without changing the diet. As shown in Figure 1, 2 cows differed in pre-feed ruminal pH (mean over 3 d = 6.88 vs. 6.14) and pre-feed total volatile fatty acid (VFA) concentration (mean over 3 d = 57 vs. 77 mM). Surprisingly, following exchange of ruminal contents, ruminal pH and total VFA concentration in both cows returned to their pre-exchange values within 24 h. Ruminal bacterial community composition also returned to near its original profile, but this change required 14 d for one cow and 61 d for another cow (Figure not shown here).
The take home message is that host animal can quickly reestablish its characteristic ruminal pH and VFA concentration despite dramatic perturbation of its ruminal microbial community. Apparently, cows within a herd consuming the same diet everyday can have dramatically different ruminal characteristics, and it may not be easy to “manipulate” or “change” a cow given the substantial host specificity.
Figure 1. Pre-feed ruminal pH and pre-feed total ruminal VFA concentrations of 2 cows. PRE = sample collected immediately before exchange. POST = sample immediately after exchange.
