By: Elaine Grings, SDSU Assistant Professor, Cow/Calf Management & Production Specialist
A diverse population of micro-organisms in the gut of ruminants allows them to digest fibrous foods that are mostly unusable by humans. New genetic tools, similar to those being used to aid selection in the whole animal, are being used to improve our understanding of the relationships among the rumen micro-organisms along with how they interact with their hosts. A review paper published in January 2014 in the Professional Animal Scientist provides an update on recent research and tools for understanding the microbiology of the rumen.
We have known that the population of organisms in the rumen is large with more than a trillion organisms per ounce of rumen contents. For many years, researchers studied rumen organisms using culturing techniques that required growing bacteria in anaerobic (no oxygen) conditions on substrates that differed depending upon the species being studied. Many rumen organisms don’t grow well in culture and it is suggested that less than 20% of rumen organisms can be cultured. This limited our ability to fully study rumen microbiology in the past. Some of the species most studied by culture techniques seem to not be the most abundant in the rumen.
New technologies, such as gene sequencing and measures of gene (genomics), protein (proteomics) and metabolite (metabolomics) expression, are now being used to better characterize species in the rumen. These tools are now more affordable and available to researchers to help them describe the diversity of organisms in the rumen and to better understand their function.
Using these tools researchers now believe that the rumen may contain over 7,000 bacterial and 1,500 archaeal (single-celled but distinct from bacteria) species along with numerous protozoa, fungi and bacteriophages. Studying these organisms by use of new approaches may lead to ways to improve efficiency of ruminant animal production and may also provide important information for other uses. New enzymes have already been discovered that can aid in breakdown of cellulosic feedstock that might be used for fuel production. A more complete understanding of methane-producing bacteria could lead to decreased methane emissions. Other unique enzymes involved in lipid metabolism have also been identified from rumen organisms using new techniques. The recently published review provides an overview of the current state of our understanding and a glimpse of where we may be headed.