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Swine & U Column: Proper diet is vital to maintaining pig gut health

By Diane DeWitte, UMN Extension Swine Educator
Originally printed in The LAND - as the August 4, 2023 Swine & U Column

The University of Minnesota will soon host its annual MN Nutrition Conference in Mankato, a gathering for nutrition professionals who work with all barnyard species. More details can be found at the end of this article.

This pig nutrition review from former UMN Extension Educator Dr. Mark Whitney highlights the importance of proper diet formulation to maintain gut health and prevent intestinal disease, especially in today’s pig production as we use fewer antibiotics. Additional discussion of probiotics and direct-fed microbials can be found in Pork Information Gateway’s (PIG) Feed Additives fact sheet.

The digestive tract serves as a direct path for disease-causing organisms (pathogens) to enter the pig and cause disease. The intestine protects the pig from pathogens in several ways, it:
  • Maintains a healthy natural community of “bugs” (microflora) in the gut.
  • Releases antibodies.
  • Restricts pathogens through the physical environment.
  • Moves food through the digestive system.
  • Produces a mucus protein (mucin) barrier.
Nutrition can greatly affect all these protections. Understanding how diet interacts and affects a healthy gut can help in developing nutritional plans to maintain or improve pig health and, in turn, performance.

Gut Health & the Role of Diet


Gut microflorae are normal “bugs” that live in the gut and aid in digestion and immunity. Greatly altering gut microflora through diet is hard because producers feed a large amount of cereal grains to provide high-energy diets at a lower cost.

Evidence shows that microflorae directly affect pathogen growth and population. Stable resident microflorae protect against intestinal pathogens in several ways.
  • Healthy microflorae compete with pathogens for nutrients.
  • Healthy microflorae produce by-products that help prevent pathogens from growing on the gut wall.
  • Resident microflora may start immune factor production, such as immunoglobulins (antibodies) and inflammatory responders.

Direct-fed microbials and probiotics

The use of probiotics or direct-fed microbials (DFM) to enhance intestinal health has been studied for many years. In fact, probiotics have been used for as long as people have eaten fermented foods. Probiotics are traditionally defined as viable microorganisms that have a beneficial effect in the prevention and treatment of specific pathologic conditions when ingested. Pigs have a diverse gut microflora, containing over 400 bacterial species: with bacterial cells outnumbering host cells by a factor of 10. One strategy to prevent pathogenic bacterial colonization of the gastrointestinal system is to include DFM in the diets of pigs.

Direct fed microbials are defined by the FDA as “a source of live (viable), naturally occurring microorganisms.” The use of “naturally occurring microorganisms” in the above definition negates the use of genetically modified microorganisms as DFM. Furthermore, DFM cannot be bacterial strains selected to produce antibiotics.

Many direct-fed microbial (DFM) products can be added to the diet or water supply to supplement or aid in building a healthy gut microflora. These products can benefit animal health and performance, especially right after weaning and in cases where conditions are good for pathogenic infections. Supplementing early nursery diets with specific carbohydrates, such as galactose, may help maintain carbohydrate balance and decrease break-down by gut bacteria. This may not be a big issue in older growing pigs but may be important for newly weaned pigs in improving their protective microflora and mucin.

Avoid sudden dietary changes

Promoting increased or continued feed intake post-weaning is key to lowering the risk of health problems and improving performance. Sudden changes in diet intake and content greatly affect microflora.

Adequate feed intake

  • Improves nutrients available for growth and immune function.
  • Decreases potential for opportunistic pathogens which are organisms that cause disease under abnormal conditions.
Each of these factors is important to optimize intake:
  • Adequate feeder space
  • Proper adjustment of feeders
  • Removal of stale or spoiled feed
  • Proper maintenance and adjustment of waterers

Volatile fatty acids

Many feed nutrients go through fermentation in the intestine. This activity produces fermentation acids, including volatile fatty acids (VFAs). Diet can greatly affect VFA levels. Providing fiber in the diet is most effective in promoting increases of VFAs. But you must also consider the negative effects on growth and feed conversion when feeding more fiber. Higher VFA levels in the intestine increase resistance to opportunistic pathogens such as pathogenic E. coli. This resistance may be partly due to the ability of VFAs to help reduce gut pH. VFAs also aid in the health of the intestinal tract by providing a ready source of energy for gut tissues. VFAs meet a large part of the energy needs for these tissues.

Higher VFA levels may increase movement of feed through the gut by increasing gastric emptying and muscle activity in the gut. Slower movement of food material in the gut can increase pathogen growth.

Stomach and intestinal pH

Stomach and intestinal pH influence the amount of nutrients available to the animal by affecting digestive enzyme activity and digestive rates. In addition, pH affects the ability of pathogens to grow in the gut.

The stomach’s low pH provides an initial barrier against pathogens. Opportunistic pathogens, such as E. coli and salmonella, grow in neutral pH conditions. Lowering pH in the gut tends to favor growth of resident bacteria, including lactobacilli. This growth contributes towards a healthy microflora. Research shows that, right after weaning, pH in the gut increases, which results in an increase in the proportion of pathogenic bacteria.

Intestinal mucins

The outer thin layer of cells in the intestine (epithelial cells) produce proteins called mucins. Mucins protect the gut from the scraping of feedstuffs and from bacterial growth. Gut mucins may bind to pathogens and thus reduce the risk of pathogens attaching to the gut wall. Researchers report that mucins are the major blockers to certain types of attaching E. coli. When mucins bind to pathogens it reduces pathogen attachment to gut tissues. In turn, this may prevent or reduce immune response and infection. Microflora can ferment mucins. Some intestinal bacteria may select certain carbohydrate parts of the mucins to use for nutrient substrates.


The University of Minnesota’s 84th Minnesota Nutrition Conference will be held on September 20-21, 2023 at the Mayo Clinic Health System Event Center, 1 Civic Center Plaza in Mankato, MN.

This event is a highly regarded and well-known Midwestern livestock nutrition forum. The conference delivers leading-edge, research-based knowledge to advance sustainable production of beef, dairy, poultry, and swine. Annually the event is presented by the Department of Animal Science, University of Minnesota, and University of Minnesota Extension.

All animal nutrition professionals in the Upper Midwest are invited to participate. Preconference symposium will start at 8:30 am on Wednesday September 20, with the Conference main session beginning at 1:30 pm. The event will wrap up at 3:00 pm on Thursday September 21.

The preconference symposium, sponsored by Danisco Animal Nutrition & Health/IFF, is “Feed Challenges? Rethinking nutrition for today and tomorrow’s productivity demands” and includes discussions by nutrition leaders in all species of livestock and poultry.

Registration will include the conference General Session, species sessions with concurrent ruminant and nonruminant presentations, light continental breakfast, lunch, break refreshments and Welcome Reception. Online preregistration is $225 through 9/15/23 with on-site registration of $275. UMN faculty/student registration is $75. To register online go to:

Diane DeWitte is a UMN Extension Educator based in Mankato and can be reached at or 507-384-1745.

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