An outstanding review of the interactions between rumen microbes and the cow was just published by researchers at the U.S. Dairy Forage Research Center in Madison, WI (J. Dairy Sci. 101:7680-7689). They focused on how we can leverage what we know about the rumen microbial population to enhance dairy cow productivity.
We all understand that the rumen is essentially a large fermentation system – about 70 to 100 liters in a mature Holstein cow – that allows the cow to thrive on otherwise indigestible fiber. There is a rich diversity of microbes that ferment the ingested feed, and these microbial communities change in response to diet, breed, and age of the animal. Importantly, and very much underappreciated, they also vary tremendously among individual animals. Over the past decades the diversity of the rumen microbial population and its presumed metabolic activity have been measured using genetic approaches.
Recent research indicates that the rumen microbial populations are heritable and sustainable within an individual cow. For example, when rumen contents from one cow are placed into the rumen of another cow, rumen pH and volatile fatty acid production returned to “normal” for that cow within a day. Exactly how and why this happens remains unknown, but it could be related to re-seeding with microbes that persist within a cow, or animal-specific salivary buffering or passage rates. Either way, this type of research indicates that the cow’s genetics play a substantial role in establishing and maintaining the rumen microbial population.
Research also illustrates the resiliency of the rumen microbes to external factors. Consequently, the rumen contents may not vary all that much except for the case of significant dietary changes. This suggests that probiotics designed with a single non-native strain to enhance milk production are not too likely to result in permanent changes in a mature rumen environment.
Looking to the future, we will need to measure the microbial population across a wide range of rumen conditions – healthy and unhealthy, low and high efficiency – and we’ll need to figure out which factors most greatly affect rumen populations. As a result, the authors of the review predict that in the future we will have genetic selection for cows that in turn select for optimal rumen microbes as the cows naturally develop. With this advanced knowledge, we will also be able to develop probiotic approaches to predictably enhance output from the rumen microbial fermentation.
The authors conclude that the rumen microbial profile might well be a new phenotypic trait in cattle. And going forward, it may be possible to expand the standard “genotype x environment” model for predicting milk production into a more accurate “genotype x environment x microbe” interaction model. Complicated, certainly, but imagine the possibilities if we could someday account for known and inherited rumen differences among cows. It would revolutionize ruminant nutrition and how we feed and manage dairy cattle.
Note: This article came from the Miner Institute's Farm Report.