Fiber foods

Transforming the way we think about fiber

October 6, 2021

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9 minute read

Fiber nutrition is still in its infancy compared to the current state of knowledge about amino acids and certain vitamins and minerals. There is growing interest in using fiber-rich ingredients due to their perceived benefits on gut health. Significant advances in carbohydrate analysis have allowed diet formulators to increase the use of fibrous ingredients in their rations, typically to improve post-weaning diarrhea, induce satiety, or improve feed costs. While some fiber-rich ingredients can help reduce diet costs, others may not be cost-effective in certain situations. We need to transform the way we think about fiber and the strategy we use to measure its success as a nutritional intervention.

Fiber refers to complex carbohydrate structures that are resistant to endogenous mammalian enzymes. Dietary fiber can be broken down by enzymes expressed by gut-inhabiting microbiota, subsequently producing fermentation by-products that provide health benefits to the animal. Not all fermentations result in beneficial metabolites; the fermentation of proteins produces putrefactive factors harmful to animal health. Fermentation of undigested protein reaching the hindgut is a major contributing factor to post-weaning diarrhea.

There are currently no recommendations for meeting fiber requirements in monogastric animals. We incorporate fibrous ingredients into the diet not because the animal needs fiber per se, but rather to induce a specific response such as improved fecal consistency or to stimulate satiety. Certain characteristics of fibers cause physiological effects on the gastrointestinal tract, the extent and location of which depend on the type of fiber. We currently characterize fiber as soluble or insoluble, as opposed to fermentable or non-fermentable, because it can be measured easily and repeatedly using available analytical procedures. However, solubility is not the same as fermentability, but soluble dietary fiber is generally fermentable faster than insoluble dietary fiber.

Soluble fiber can increase digesta viscosity and delay gastric emptying. Stickiness can impose more problems in poultry than in pigs, but can also play an important role in the growth of the young pig. Fermentation of soluble fiber in the hindgut produces organic acids which are used as an indirect energy source for the host animal. Significant amounts of organic acids can lower pH with antimicrobial effects that act as a competitive exclusion strategy by commensal and beneficial bacteria to outcompete pathogens. Fermentation byproducts also stimulate the production of goblet cells to increase mucus secretion, improving intestinal permeability against toxins and pathogenic bacteria. On the other hand, insoluble fiber increases the volume and stimulates the peristaltic movement of food in the intestinal tract. It also avoids stasis and limits the proliferation time of pathogenic and opportunistic bacteria. Pathogens can also adhere to insoluble fiber, preventing attachment to the intestinal epithelium. The balance between soluble and insoluble fiber will depend on the animal’s desired response.

Fiber fermentation in the hindgut results in the production of short-chain fatty acids, including acetate, propionate, and butyrate. The beneficial role of butyric acid in gut health is widely accepted in the field of nutrition. Controversy exists in its form of application and whether it is more effective to supplement via diet or by stimulation of microbial production in the host. Several bacterial species inhabiting the hindgut produce butyric acid by fermentation of prebiotic fibers. It is an effective means of delivering butyric acid to the large intestine where it evokes benefits for the animal. However, there are also several species that ferment undigested proteins that reach the hindgut, resulting in toxic byproducts that could damage the intestinal epithelium. It is precisely for this reason that nutritionists reduce crude protein levels in early nursery rations in production systems with limited use of antibiotics or zinc oxide.

Many of our common fiber-rich ingredients contain non-fiber nutrients that can be utilized by the animal. Oats are a good source of prebiotic β-glucans, but also a good source of starch. Distillers Grains with Solubles (DDGS) contain high levels of insoluble fiber as well as an economical source of amino acids. Sugar beet pulp is high in soluble fiber, which makes it highly fermentable, but this ingredient also contains a high concentration of insoluble fiber. The point here is that traditional sources of fiber-rich ingredients rarely contribute only fiber to the diet. Some ingredients can even introduce mycotoxins and other toxic compounds into the feed which will inhibit growth.

The different types of carbohydrate structures among fiber-rich ingredients require distinct feeding strategies. For example, post-weaning diarrhea is often multifactorial, so several strategies must be implemented to address the problem, ranging from diet to environmental conditions in which the pigs find themselves. Antibiotics and the therapeutic use of zinc oxide have traditionally masked the harmful effects of some of the causative agents. Without these technologies, strict biosecurity protocols, proper husbandry practices, and specific diet formulation strategies must be implemented in conjunction. From a nutritional standpoint, minimizing undigested protein and rapidly fermentable carbohydrates reaching the hindgut by using the right fibers can help improve fecal consistency. The challenge with fiber supplementation is identifying when to use which type of fiber ingredient or supplement.

It is important to take into account the concentration of total dietary fiber in the complete ration. Increasing dietary fiber can lead to unintended consequences if the ration is not balanced to accommodate higher levels of fiber. Although the animal can use fermentation by-products as an energy source, high levels of dietary fiber can also decrease the digestibility of certain nutrients. It is important to know which ingredients contribute fiber in the diet. For example, a ration based on wheat and barley will have a higher concentration of soluble and fermentable fibers compared to a diet using corn as the main cereal.

Is it possible to obtain the favorable effects of fiber without sacrificing performance? Yes, but this requires a thorough understanding of the entire dietary fiber fraction using appropriate analytical techniques. The crude fiber method says very little about the true fiber content of most pet foods, hence the term crude. Detergent fiber methods are an improvement over crude fiber, but don’t tell the whole story. Total dietary fiber, specifically insoluble and soluble fiber including low molecular weight sugars, represents a more complete picture of the fiber fraction and its potential consequences when fed to an animal.

Raising food animals is rooted in progress and innovation. Stakeholders are constantly adapting to the ever-changing regulatory landscape that dictates how the industry can produce and market its products. Many parts of the world are limited in feeding technologies that can be used to improve growth performance. The use of conventional antibiotic growth promoters has declined over the years and ractopamine hydrochloride is banned in many countries. More recently, pharmacological levels of zinc oxide have been phased out in the European Union. The next innovative power solution may prove effective, but legislation will dictate its use if the science is there to back it up. An ingredient like a functional fiber is unlikely to have any regulatory objections because of how it is produced and how it affects the animal.

New generation functional fibers are active ingredients that have beneficial physiological effects on animals. HP FiberBoost is an enzyme-treated functional fiber that is designed to combine the physical benefits of insoluble fiber with the gut health boosting effect of prebiotic carbohydrates. Specific enzymes hydrolyze sections of the carbohydrate structure to reduce viscosity while maintaining the desired structural functionality of the fiber. This targeted cleavage enhances the concentration of prebiotic carbohydrate moieties that stimulate the proliferation of beneficial bacteria in the hindgut, resulting in the production of significant amounts of butyric acid.