Swine microbiome: What does it all mean?
Understanding gut microbiota critical to improving production, profitability
By Savannah Lynn Locke, C. Robert Dove and Todd Callaway
The term microbiome is mentioned commonly today, from commercials, to TV shows and newspaper stories, but what exactly is the microbiome? Microbiome is simply a term for the genetic material of the microbial population in the gut of pigs.
The native microbial population that is found through the gut of pigs plays an important role in nutrient metabolism, maintenance of structural integrity of the gut mucosal barrier (keeping the outside world out of your pigs’ tissues), and protection from pathogen colonization.
This complex microbial population within contains millions of bacteria in each ounce of digesta, and this dense population is also very diverse, acting as a complex and dynamic ecosystem.
As pigs eat feed and it reaches the hind gut, microbes are able to degrade (ferment) feedstuffs to sustain the bacteria living inside the gut. The microbial degradation of feeds can impact efficiency, profitability, sustainability, health, food safety and carcass quality of swine. However, studying the microbiome can be very complex as there are thousands of prokaryotic, eukaryotic and viral species living inside the gut, and identifying how each microbial species is affected can be fiendishly difficult.
As the microbes break down feeds, they must ferment it (think wine and beer and production) and produce end products such as CO2, methane (a greenhouse gas), and volatile fatty acids (VFAs). Acetate, butyrate and propionate are the VFA's produced in the gut that are used by the pig for energy, and can account for 10-15% of the pigs’ energy budget.
Without a microbial population, pigs would still survive, but they would have less energy available, as the microbial population provides an opportunity to get a “second bite at the apple” in terms of harvesting dietary carbon and energy for your pigs to utilize.
Acetate is the acid found in vinegar, and it provides energy and impacts red blood cell generation. Propionate is another VFA that is converted to glucose in swine tissues where it can aid with muscle function. Butyrate also is used for energy, but provides energy to the gut epithelial tissue, and this helps ensure the integrity of the gut barrier.
However, we still don’t know which microbes produce which VFA and other end products that can impact animal health and gut motility. As we learn more about the microbial population and the end products of each microbe, we can start to determine which are “good” and which are “bad” members of the population from our perspective as swine producers.
Microbial balance matters, because a dietary or environmental change can lead to an imbalance which leads to microbial dysbiosis, which is an imbalance. Much as a wildfire causes drastic changes in the animal and plant populations of a forest, dysbiosis can be very disruptive to the microbial ecosystem in the gut.
Dysbiotic impacts can include inflammation, diarrhea, non-growth energy expenditure and translocation of pathogenic bacteria such as Salmonella. An imbalance can also allow for opportunistic pathogens to disrupt the gut environment and to cause illness in the pigs, or act as a foodborne pathogen and affecting human pork consumers.
However, there are several products that can manipulate the microbial population to improve production efficiency. These tools include: antibiotics, antimicrobials, prebiotics, probiotics, postbiotics minerals and diet composition all have the ability to influence pH, bacterial populations and activities, and enzymes.
While the microbial population in the gut of swine is very diverse, some of the most prevalent bacterial species include: Escherichia, Lactobacillus, Prevotella, Clostridium, Bacteroides, Oscillospira, Fusobacterium, Paraprevotella, Treponema, and Bacillus. As swine grow and different diets are implemented, different groups of bacteria are impacted.
A good way to help manage the gut microbiota is to understand the inhibition of metabolic pathways, implement immunization and vaccination pathways, feed the correct diet, lower stress, and utilize eubiotic (feed additives which impact the native microbial population) products.
The microbial population of the gut is very dense and very diverse, and in many ways, it is like living in a very bad neighborhood, full of competition for the necessities for survival. Microbes in the gut are in constant competition with each other in order to survive, thrive and produce more bacteria.
Depending on the nature of each microbe and its survival strategies, each species have different strategies that allow them to survive in different specific locations within the gut and to thrive on specific feedstuffs.
Microbes can utilize and store specific nutrients needed for survival, out-competing their competitors. Other microbes instead physically block binding sites for competitors. In other cases, the microbes could begin producing acids, or antimicrobial peptides or antibiotics that can destroy their opponents.
Understanding the biochemical pathways, end product connections, degradation rates, and niches are key in understanding how these bacteria can impact your swine productivity and health.
The next step that we are pursuing includes determining which diet components impact each specific microbe and microbial environmental niche, what drives changes in the end products under various conditions, and how we can maximize the energy harvested by the host animal, thus maximizing growth of the pig.
Understanding the gut microbiota is critical to improving production, sustainability, food safety and profitability for your operation.
References Luo, Y., Ren, W., Smidt, H., Wright, A. G., Yu, B., Schyns, G., McCormack, U. M., Cowieson,
A. J., Yu, J., He, J., Yan, H., Wu, J., Mackie, R. I., & Chen, D. (2022). Dynamic distribution of gut microbiota in pigs at different growth stages: composition and contribution. Microbiology spectrum, 10(3), e0068821. https://doi.org/10.1128/spectrum.00688-21
Locke is a doctoral graduate student, Dove is the undergraduate coordinator and swine extension specialist, and Callaway is an associate professor of ruminant nutrition and microbiology, and preharvest food safety, all at the University of Georgia. Cover photo courtesy of Locke.
