Gut bacteria deserve renewed focus

With the FDA’s new veterinary feed directive (VFD) rules changing the way some feed-grade antimicrobials are used on the farm, other options are gaining more attention. Among those is managing the microbiome.¹

This refers to the bacterial populations located all along the gastrointestinal tract of animals, said Jamie Ortman, animal science graduate student at South Dakota State University. “These bacteria play an integrative, symbiotic role with their swine hosts,” she added.

Some of the beneficial effects in swine production include improved feed conversion, growth performance and decreased pathogen load. The greatest response can be seen post-weaning by reducing stress and altering the microbiome with non-traditional feed additives.

Post-weaning is a challenging transition for young piglets for many reasons, not the least of which is the animal’s underdeveloped immune system and increased exposure to bacterial infections.

Minimizing challenges

Over time, producers have developed strategies to minimize the challenges that piglets encounter, such as utilizing phase feeding, high-quality feedstuffs, antibiotics and a range of management practices, Ortman told Pig Health Today.

Because nursery pigs have a highly fluctuating microbiota, manipulating the microbiome may help them adapt to their new feeding situations, as well as address diarrhea and/or improve feed efficiency.

“It’s likely that feeding sub-therapeutic levels of antibiotics altered the microbiome specifically for piglets in highly stressful times, such as weaning and transitioning to solid feed,” Ortman said. “Speculation is that the microbiome uses several mechanisms to reduce infections and improve growth performance in stressed piglets.”

She pointed to research suggesting that manipulating the microbiome provides increased bacterial diversity, earlier establishment of a beneficial “core” bacteria and earlier immune regulation.

Benefits and options to managing bacteria

Overall, the benefits are likely a result of a shift in the proportion of different types of bacteria within the gut versus an actual population change.

Researchers have reported that the addition of spent cider yeast significantly changed the piglets’ microbiota by reducing high levels of pathogenic bacteria while encouraging the growth of more beneficial bacterial populations.  Adding cider yeast reduced pathogenic enterobacteria, such as Salmonella and Escherichia spp.

In an alternate study, researchers reported that adding certain probiotic species increased piglets’ feed intake and improved growth performance.

“The researcher did not note any changes to the gut microbiome composition; however, he did see a decline in a specific family of bacteria within the treatment group as compared to the control group,” Ortman said.

Fewer options

FDA’s new VFD rules removed performance claims — improved growth rate and feed conversion, for example — from feed-grade antibiotics deemed medically important to humans. That left the US pork industry with only a few medications with these claims and more incentive to focus on microbiome-management and alternatives such as probiotics and unconventional ingredients that alter the bacterial populations to increase diversity and immune modification.

Ortman cited the example of adding Lactobacillus casei to the piglet diet, as it has been identified to reduce inflammation, decrease pH and increase the Immunoglobulin A antibodies, thus boosting the immune response within the pig’s gastrointestinal tract

“The immune response can reduce the likelihood of infection within the gut, which can result in increased growth until market weight,” she added.

Fermented feeds are another prospect to improve pig performance. Past research suggests that fermented feeds may reduce pathogens along the gut, via decreased pH and competitive exclusion, which could lead to increased growth performance of the pigs.

“Ultimately, the study of the microbiome is just getting started, as we learn which (bacteria) species colonize the gut and what their function may be in the pig,” Ortman said. “At the end of the day, microbiology has the potential to influence production rates and decrease production losses via shifts in the microbiome.”

¹ Ortman JL, Nold R. How Gut Bacteria Can Improve Swine Production. South Dakota State University Extension.