- Gut microflora, diet and increases in pathogens interact in swine digestion.
- Formulating diets is a key tool for maintaining gut health and preventing intestinal disease, especially when using less antibiotics.
The digestive tract serves as a direct path for disease-causing organisms (pathogens) to enter into 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 of 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.
How the gut stays healthy and how diet plays a role
Gut microflora 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 microflora directly affect pathogen growth and population. Stable resident microflora protect against intestinal pathogens in several ways.
- Healthy microflora compete with pathogens for nutrients.
- Healthy microflora 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.
Feeding direct-fed microbial products
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.
Sudden changes in diet can harm microflora
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.
Making sure pigs have adequate feed intakes
- Decreases potential for opportunistic pathogens.
- Opportunistic pathogens are organisms that cause disease under abnormal conditions.
- Improves nutrients available for growth and immune function.
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.
VFAs help protect the gut from pathogens
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 to 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 influences
- The amount of nutrients available to the animal by affecting digestive enzyme activity and digestive rates.
- 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.
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.
Reviewed in 2018