By Joel DeRouchey, Mike Tokach, Jason Woodworth, Bob Goodband, Jordan Gebhardt and Katelyn Gaffield of Kansas State University
The use of fiber in nursery diets is mostly related to the purpose of ameliorating post-weaning diarrhea. Unlike energy and nutrients, there are no firm recommendations of fiber inclusion in nursery diets. Diets rich in dietary fiber generally have lower nutritive value for nursery pigs because digestive enzymes are not suited for degrading fiber. However, dietary fiber components seem to have beneficial effects on gut health and development, particularly to help reduce post-weaning gut disorders.
Fiber is classified as soluble or insoluble based on fiber solubility in water. The fiber characteristics relevant to swine nutrition include fermentability, viscosity and hydration. Natural fibrous feed ingredients are usually composed of both soluble and insoluble fiber.
In general, in the immediate post-weaning period, the use of ingredients with concentrations mainly of insoluble fiber (e.g. wheat middlings, wheat bran or oat hulls) are preferred over ingredients with main concentrations of soluble fiber (e.g. sugar beet pulp), but in later nursery the use of soluble fiber in diets might be beneficial to promote gut health and development.
Insoluble Fiber
The use of insoluble fiber (resistant to fermentation) is recommended in post-weaning diets as it increases the passage rate, prevents harmful bacterial growth and improves intestinal morphology and microbial balance in the intestine. Multiple research studies have concluded that use of insoluble fiber in piglets challenged with E. coli decreased the cases of diarrhea due to the reduced ability of E. coli adhesion to the small intestine.
Insoluble fibers are relatively resistant to fermentation in the hindgut and do not contribute much to production of volatile fatty acids. The presence of insoluble fibers increases fecal bulkiness and accelerates digesta passage rate, which prevents proliferation and colonization of pathogens. Insoluble fibers include cellulose and hemicellulose. Feed ingredients such as wheat middlings, wheat bran, rice hulls, oat hulls and distillers dried grains with solubles have predominantly insoluble fiber concentrations.
Soluble Fiber
Soluble fibers are more rapidly fermented in the hindgut and produce more volatile fatty acids, such as acetate, propionate and butyrate, which are used as sources of energy to promote gut development. Soluble fibers also promote a prebiotic effect by enhancing beneficial bacteria fermentation and production of volatile fatty acids while reducing gut pH to eliminate pathogens.
The presence of soluble fibers increases digesta viscosity, which delays digesta passage rate, interferes with nutrient digestion, and predisposes proliferation and colonization of pathogens. However, soluble fibers have better solubility, swelling capacity, water holding capacity and water-binding capacity that are important for digestion. Soluble fibers include pectins, gums and β-glucans. Feed ingredients such as sugar beet pulp and citrus pulp have predominantly soluble fiber.
Ongoing research is being conducted to determine the ideal insoluble:soluble ratio at different time points post-weaning. Application of how both commonly available fiber rich ingredients and specialty manufactured fiber ingredients can be practically and economically used to increase fecal dryness without reducing nursery pig performance is on-going.
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