Transform our perception of fiber
Fiber nutrition is still in its infancy compared to current in-depth knowledge of amino acids and some vitamins and minerals. There is growing interest in the use of high fiber ingredients due to their perceived benefits on gut health. Significant advancements in carbohydrate analysis have enabled 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 high fiber ingredients can help lower diet costs, others may not be cost effective in certain situations. We need to transform our perception of fiber and the strategy we use to measure its success as a nutritional intervention.
Fiber refers to complex carbohydrate structures resistant to endogenous mammalian enzymes. Dietary fiber can be broken down by enzymes expressed by the microbiota inhabiting the intestine, subsequently producing fermentation by-products that provide health benefits for the animal. Not all fermentations result in beneficial metabolites; the fermentation of proteins produces putrefactive factors which are harmful to animal health. Fermentation of undigested protein reaching the hindgut is a major contributor to post-weaning diarrhea.
There are currently no recommendations for meeting the fiber requirements in monogastric animals. We incorporate fibrous ingredients into the diet not because the animal has a need for 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 depends on the type of fiber. We currently characterize fiber as soluble or insoluble, as opposed to fermentable or non-fermentable, as it can be easily and repeatedly measured using available analytical procedures. However, the solubility is not the same as the fermentability, but soluble dietary fiber is generally more rapidly fermentable than insoluble dietary fiber.
Soluble fiber can increase the viscosity of the digesta and delay gastric emptying. Viscosity 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 the pH with antimicrobial effects that act as a competitive exclusion strategy by commensal and beneficial bacteria to outperform pathogens. Fermentation byproducts also stimulate the production of goblet cells to increase mucus secretion, thus improving intestinal permeability against toxins and pathogenic bacteria. On the other hand, insoluble fiber increases bulk and stimulates the peristaltic movement of feed through the intestinal tract. It also prevents 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 desired response of the animal.
Fermentation of fiber 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 recognized in the field of nutrition. Controversy exists in its form of application and whether it is more effective to supplement via diet or by stimulating microbial production within 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 suggests benefits for the animal. However, there are also several species that ferment the 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 the crude protein levels of early nursery diets in production systems with limited use of antibiotics or zinc oxide.
Many of our common high fiber ingredients contain nutrients other than fiber that can be used by the animal. Oats are a good source of prebiotic β-glucans but are also a good source of starch. Dried Distillers 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 high fiber ingredients rarely contribute only fiber in the diet. Some ingredients can even introduce mycotoxins and other toxic compounds into the diet that will inhibit growth.
The different types of carbohydrate structures among the high fiber 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 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, appropriate husbandry practices and specific diet formulation strategies must be implemented jointly. From a nutritional standpoint, minimizing undigested protein and rapidly fermenting carbohydrates reaching the hindgut by using the right fiber can help improve fecal consistency. The challenge of fiber supplementation is to identify when to use what kind of ingredient or supplement of fiber.
It is important to consider the concentration of total dietary fiber in the complete ration. Increasing dietary fiber can have unintended consequences if the ration is not balanced to accommodate higher levels of fiber. Although the animal can use the byproducts of fermentation for energy, high levels of dietary fiber can also decrease the digestibility of certain nutrients. It is important to know which ingredients contribute to fiber in the diet. For example, a ration based on wheat and barley will have a higher concentration of soluble and fermentable fiber compared to a diet using corn as the main grain.
Is it possible to achieve the favorable effects of fiber without sacrificing performance? Yes, but it does require 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 raw materials, hence the term crude. The fiber detergent methods are an improvement over crude fibers, but do not provide the full story. Total dietary fiber, looking specifically at insoluble and soluble fiber, including low molecular weight sugars, represents a more complete picture of the fiber fraction and its potential consequences when given to an animal.
The breeding of food animals is deeply 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 the feeding technologies that can be used to improve growth performance. The use of conventional growth promoting antibiotics has declined over the years and ractopamine hydrochloride is banned in many countries. More recently, pharmacological levels of zinc oxide are being phased out from the European Union. The next innovative feeding solution may prove to be 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 opposition 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 the animal. HP FiberBoost is an enzyme-treated functional fiber that is designed to combine the physical benefits of insoluble fiber with the stimulating effect of prebiotic carbohydrates on gut health. Specific enzymes hydrolyze sections of the carbohydrate framework to reduce viscosity while maintaining the desired structural functionality of the fiber. This targeted cleavage increases the concentration of prebiotic carbohydrate moieties which stimulate the proliferation of beneficial bacteria in the hindgut, resulting in the production of significant amounts of butyric acid.