SPECIAL REPORT: Using the microbiome to enhance animal health, productivity
From the 2024 Kemin Intestinal Health Symposium
By Ann Hess
If Joshua Lyte could emphasize one key point regarding the microbiome, it’s that bacteria are not dumb bugs. They actively participate in animals’ stress response and are influenced by it.
“It's a host-microbe bidirectional communication dialogue,” Lyte said. “That host-microbe bidirectional dialogue is, in part, mediated by stress-related neurochemicals.”
However, the microbiologist in Poultry Production and Product Safety Research with the USDA Agricultural Research Service says when it comes to microbiota research today, it’s mainly been a “fishing expedition.” Lyte told the audience during the 2024 Kemin Intestinal Health Symposium, there needs to be a move towards starting with “function-driven hypotheses” or an “evidence-based framework for that host-microbe bidirectional dialogue” before research can jump further into the microbiome.
The reason why stress-related neurochemicals are relevant for monogastric and ruminant microbiome research, Lyte said, is because it represents an evolutionary form of host-microbe interaction that is common across poultry and livestock species. As an evidence-based form of host-microbiota interaction, the targeted modulation of stress-related neurochemicals can serve as a launching pad for the development of impactful microbiome-based applications in food animal production.
“Neurochemicals are a very big class of compounds, but today we are talking about the fight or flight neurochemicals, so stress-related monoamines, norepinephrine, dopamine, serotonin and others,” Lyte said. “Neurochemicals are an interkingdom molecular language of stress.” This field of research is called Microbial Endocrinology.
Those stress-related neurochemicals can be released directly into the gut mucosa and lumen to cause compositional, as well as functional, changes in the bacteria of the animal’s gut. On top of that, many plants harvested for animal feed synthesize and use the same neurochemicals that are found in animals – and recognized by bacteria – in order to deal with environmental stress. The question then becomes: How does the impact of a changing climate on crop production alter the neurochemical profiles of poultry and livestock feed? Is there an impact of what is in feed, beyond the consideration of meeting nutritional requirements, on host-microbe interaction in the gut?
In recently published work in broiler chickens, Lyte and his team examined the neurochemical biogeography, or the concentration and distribution of neurochemicals throughout the gastrointestinal tract.1
“What's really interesting is that we found neurochemicals not just in the tissue of the gut but in the luminal content of each region of the chicken intestinal tract,” Lyte said. For example, norepinephrine that can influence foodborne pathogen carriage in the gut was found in luminal content of each region of the chicken intestinal tract.
“What if your bird is stressed?” Norepinephrine and other stress-related neurochemicals have been shown to drive Salmonella carriage. Sticking with the evolutionary theme of neurochemical-based host microbe interaction, norepinephrine can also increase E. coli O157:H7 within the porcine and bovine gut mucosa.
And it's not just relevant for the animal gut, stress-related neurochemicals are also important for the respiratory tract. Stress-related neurochemicals affect many porcine respiratory pathogens such as Actinobacillus pleuropneumoniae, Bordetella bronchiseptica, Mycoplasma hyopneumoniae and Pseudomonas aeruginosa. In cattle, stress-related neurochemicals can have an impact on bovine respiratory disease (BRD), including Mannheimia haemolytica, a bacterial component of BRD.
What steps can livestock producers take on-farm now to decrease these stress-related neurochemicals in their animals? A launching point for swine, poultry and cattle production is to tackle transport stress, Lyte said.
“Two to three hours of transport stress can cause the emergence of bacterial strains that weren't there before the transport stress started,” Lyte said. “So, could stress-related neurochemicals be driving both compositional and functional shifts in your animal’s microbiome?”
Lyte said it’s important to also understand your animals’ stress phenotype, as the host’s own stress response plays a role in shaping the microbiome and the amount of stress-related neurochemicals that are normally found in the gut.
“Microbial endocrinology can serve as an evidence-based framework for the development of function-driven hypotheses that can accelerate the application of the microbiome to improve poultry and livestock production,” Lyte concluded.
Watch the full presentation from Dr. Lyte and access all content from the 2024 Kemin Intestinal Health Symposium at kemin.com/symposium.
1 Lyte, JM, et al. 2022. A neurochemical biogeography of the broiler chicken intestinal tract. Poultry Science 101 (3).