A Healthy Pig Gut Stimulates Healthy Growth

by Boehringer Ingelheim Animal Health USA Inc./April 21, 2021

One critical aspect of achieving and maintaining a healthy herd is through gut health. When intestines are healthy and functioning properly, pigs are more capable of achieving their full genetic potential. In addition, a healthy gut with immunity to infection can reduce the need for antibiotics and increase the opportunity to raise pigs in a sustainable manner.

Having tools to promote a healthy gut is very important to achieve maximum efficiency and overall health on the farm.^1,2

The intestinal microbiome: vital defense against infection

The genetic repertoire of the gut microbiome has been estimated to be almost 100 times greater than that of the host, with more cells and over 1,000 species of bacteria, fungi, viruses and phages. With this diversity, the microbiome has the potential to provide numerous biological activities that the pig lacks.^3,4 Protecting the microbiome is essential, and accomplished through safe handling, biosecurity protocols, proper sanitation and nutrition, and vaccination when appropriate.²

Functions of a balanced microbiome:^4,6

Development and modulation of the immune system
Providing colonization resistance to pathogens
Breakdown of food and fiber for energy production
Maintenance of intestinal peristalsis and function
Synthesis of short-chain fatty acids (butyrate, acetate, propionate), vitamins and other essential metabolites

Functions of butyric acid/butyrate:^7,8

Is the main energy source of intestinal cells
Modulates immunologic processes in the intestines
Without it, intestinal infections (such as Salmonella) can more easily take hold, due to decreased colonization resistance

The mucous layer: the intestines’ protective shield against pathogens

As the first line of defense against invading pathogens in the intestine, a healthy mucus layer is essential for the gut health of the pig. When this layer is weakened, innate immunity and colonization resistance are compromised, and pathogens and commensal bacteria can more readily cause harm.⁹

Functions of the mucus layer:

Protection of the intestinal mucosa against
- Physical damage
- Triggering of inflammatory reactions, due to contact with pathogens and also commensal bacteria
Important component of nonspecific defense – first line of defense against pathogens
- The mucus layer is rich in antibodies and antimicrobial peptides

The intestinal mucosal immune system: mission control for pig health

A pig’s intestine, along with its mucosal immune system, plays a significant role in controlling and preventing disease. In fact, the intestine contains the largest number of immune cells of any tissue in the body.¹⁰ When the intestinal immune system is compromised, even a low exposure to pathogens can stimulate inflammation or illness.

Functions of the intestinal immune system:

It guards the large contact surface between the outside world and the body; keeps pathogens and also commensal bacteria from entering the body.
The crux of the defense lies in the rapid destruction of infected cells and invading pathogens, while not developing an exacerbated unnecessary response to commensal microbiota.
The immune system of the intestine relies on unique characteristics, such as a specific antibody type called IgA, which can be secreted to bind to pathogens in the intestinal lumen as well as T cells, which can be home to the specific intestinal site of infection.
An important type of T cell in the intestines is cytotoxic T-cells (CD8+), which can eliminate infected cells, including epithelial cells.
Macrophages are also important, and phagocytize foreign, infected or dead cells and generate pro-inflammatory cytokines. Macrophages are activated by T-helper cells (CD4+), which secrete stimulatory cytokine interferon γ.

Here’s why gut health matters in the fight against Lawsonia

When a pig’s microbiome and intestine is compromised by ileitis, it not only suffers from the direct consequences of the disease, it increases risk of further infection by Salmonella and other pathogens. The best way to beat ileitis is to follow the ileitis infection chain. Using a non-harmful form of the bacterium administered through the pig’s water supply, Enterisol^® Ileitis stimulates a direct immune response in the intestine where the infection actually occurs. In addition, oral delivery through the water supply is a convenient, labor-saving method that provides quick “blue nose” verification it’s been administered. By helping to build the antibodies that prevent ileitis, ENTERISOL ILEITIS provides stronger, more active protection for herd gut health.

Lawsonia Intracellularis significantly alters the microbiome and intestinal structure:¹⁴

Lawsonia can alter the bacterial community present in the gut, including Clostridium species, which may be important to produce butyrate.
Colonization resistance can be compromised – promoting infection by other pathogens such as Salmonella and Brachyspira hyodysenteriae.
Villi height can be decreased – decrease in villi height would be expected to have a direct impact on the capacity of the pig to absorb nutrients.¹

Lawsonia intracellularis damages the mucus layer.¹⁵

Lawsonia intracellularis flagella penetrate the previously intact mucus later to reach the enterocytes. Once they have invaded the crypt epithelial cells, Lawsonia bacteria significantly affect the cells’ physiological processes.

Lawsonia infection causes:

Loss of mucus-producing goblet cells
Downregulation of mucin production in the few remaining goblet cells
Altering normal increased cell proliferation

Effects on infected pigs:

Significant impairment of nonspecific immune defense
Pathogens and commensal bacteria can reach the intestinal mucosa unimpeded
Inflammatory reactions in the intestinal mucosa caused by pathogens and commensal bacteria

Lawsonia intracellularis can cause local immune suppression:^13,16

Loss of cytotoxic T-cell population, which removes infected epithelial cells
Decreased infiltration of the infected area by B-lymphocytes, and therefore lower antibody production

Immune suppression caused by Lawsonia intracellularis:

Makes it easier for intestinal pathogens to enter the body
Makes it possible for an inflammatory reaction or illness to occur, even with low exposure to pathogens
Is the basis for persistent intracellular bacteria

For more information about how you can support gut health in your herd, watch the video listed below and contact your Boehringer Ingelheim representative today:

Production Loss from Subclinical Enteric Disease in Swine, featuring Dr. Nick Gabler from Iowa State University

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References

¹ Moeser A Pohl CS, Rajput M. Weaning stress and gastrointestinal barrier development: Implications for lifelong gut health in pigs. Anim Nutr 2017;3(4):313–321.

² Niederwerder MC. Role of the microbiome in swine respiratory disease. Vet Microbiol 2017;209:97–106.

³ Gilbert JA Blaser MJ, Caporaso JG, et al., Current understanding of the human microbiome. 2018;24(4):392–400. 2018

⁴ Isaacson R, Kim KB, The intestinal microbiome of the pig. Anim Health Res Rev 2012;13(1):100–109.

⁵ Leitte F, Singer R, Ward T, et al., Vaccination against Lawsonia intracellularis decreases shedding of Salmonella enterica serovar Typhimurium in co-infected pigs and alters the gut microbiome. Sci Rep 2018;8(1)2857.

⁶ Amon P, Sanderson I. What is the microbiome? Arch Dis Child Educ Pract Ed 2017;102(5):257–260.

⁷ Bedford A and Gong J. Implications of butyrate and its derivatives for gut health and animal production. Anim Nutr 2018;4(2):151–159

⁸ Kim HB and Isaacson RE. Salmonella in swine: microbiota interactions. Annu Rev Anim Biosci 2017;5:43–63.

⁹ Ducarmon QR, Zwittink RD, Hornung BVH, et al. Gut microbiota and colonization resistance against bacterial enteric infection. Microbiol Mol Biol Rev 2019;83(3):e00007–19.

¹⁰ Mowat AM, Agace WW. Regional specialization within the intestinal immune system. Nat Rev Immunol 2014;14(10):667–685.

¹¹ Gebhart CJ and Guedes RMC. Lawsonia intracellularis. Gyles CL, Prescott JF, Songer G, Thoen CO, eds. Pathogenesis of bacterial infections in Animals. United Kingdom: Blackwell Publishing. 2010;503–512.

¹² Patterson S, Kim HB, Borewicz K, Isaacson RE. Toward an understanding of Salmonella enterica serovar Typhimurium persistence in swine. Anim Health Res Rev 2016;17(2):159–168.

¹³ MacIntyre, Smith D, Shaw D, et al. Immunopathogenesis of experimentally induced proliferative enteropathy in pigs. Vet Pathol 2003;40(4):421–432.

¹⁴ Borewitz KA, Kim HB, Singer RS, et al. Changes in the porcine intestinal microbiome in response to infection with Salmonella enterica and Lawsonia intracellularis. PLoS One 2015;10(10):e0139106.

¹⁵ Bengtsson RJ, MacIntyre N, Guthrie J, et al. Lawsonia intracellularis infection of intestinal crypt cells is associated with specific depletion of secreted MUC2 in goblet cells. Vet Immunol Immunopathol 2015;168(1–2):61–7.

¹⁶ Vannucci FA, Gebhard CJ. Recent advances in understanding the pathogenesis of Lawsonia intracellularis infections. Vet Pathol 51, 2014;51:465–477.