Fiber in Animal Nutrition

17 2.1 Introduction Without doubt fiber is an important nutrient in swine nutrition contributing to animal health and welfare. Aminimum level of fiber has to be included to maintain physiological function of the gut. Especially during gesta- tion, weaning or a change of feed attention should be given to the amount and type of fiber fed. A major concern when including fiber, is that high fiber diets are associated with dilution in terms of energy and reduced di- gestibility of the feed. But these negative attributes are determined by the inclusion rate and the fibrous characteristics of individual feed components. Different fibrous feed stuffs are available on the market. These fiber sources differ de- pendant on their origin but can also involve certain risks. These risks are associated to feed hygiene (mycotoxins, pests) and other quality properties (dust, flowability). This makes close evaluation obligatory. Nutritionists have long been aware of the importance of fiber in swine nutrition. In recent years the legislation inmany countries has additionally provided for a minimum crude fiber or roughage supplementation in gestating sows. This is accompanied by an increasing awareness for the fiber requi- rements of piglets and hogs. 2.2 Fiber classification It is well accepted that fiber is essential for gut health, gut motility and overall well being of pigs. Thereby two aspects of fiber are in the center of attention and often go along with each other: 1) solubility and 2) fermentability. Cellulose and the lignin-cellulose complex not only fill the gut due to their insolubility they also have a good water binding capa- city which additionally contributes to their bulking features. The bulking effect and the excitation of intestinal receptors by the edges of the particles promote the onward movement of the digesta in the gut. A suffici- ent fill of the gut and good peristalsis of the intestine contributes to satiation and prohibits constipation in and around farrowing – i.e. reducing the risk of MMA. Maintaining the physiological function of the gut is also a challenge in newly weaned piglets. In this transition phase insoluble fiber can contri- bute to a healthy gut. Furthermore insoluble and indigestible fiber can also suppress di- arrhea. If the fiber provides a large surface, this supports the proliferation of probiotic bacteria and the good water binding capacity regulates potential excess liquid in the gut lumen resulting from osmotic imbalances during diarrhea. Soluble and fermentable f ibers in turn provide the nutritional basis for lactic bacteria in the hind gut. Especially pectin plays an important role when providing fermentable fiber to sows because it is themain component in common feedmaterials like sugar beet pulp and apple pomace. In the course of bacterial degradation short chained fatty acids (SCFA) are released and contribute to daily energy supply. While the energy supply fromglucose digestion (derived from cereals) in the small intestine is associated to insulin peaks shortly Fiber in Swine Nutrition Astrid Bosse © ERLING Verlag