Dietary fiber in swine diets: Impact on fiber degradation, disaccharidase activity, nutrient digestibility, uptake and intestinal histology along the gastrointestinal tract.

摘要

The purpose of the following experiments was to document the physical, chemical and physiological impact of dietary fiber along the gastrointestinal tract of swine. The experiment presented in Chapter II determined the level of dietary fiber degradation along the digestive tract following the intake of fermented and non-fermented liquid cereal (barely and wheat) diets. The experiment presented in Chapter III showed the impact of dietary soybean hulls (SH) on nutrient digestibility and consequent energy substrate utilization in the pig. The final experiment presented in Chapter IV documented the impact of soybean hulls on gastrointestinal tract physiology.;Results from the first experiment indicate that fermentation can reduce whole cereal grain (barley and wheat) DM content, however following fermentation the level of cereal DM between barley and wheat was similar. Fermentation can also decrease the level CP, fat and sugar present in these cereal grains; altering the chemical properties of cereal grains prior to feeding. Feeding growing pigs fermented barley diets had a greater impact on reducing fecal DM, OM and protein compared to pigs fed the fermented wheat diets. Total ileal NSP digestibility tended to decrease while fecal NSP digestibility was not affected by feeding pigs fermented liquid cereal diets. Therefore, the impact of fermentation can also vary depending on the type cereal grain used. Ultimately feeding growing pigs these fermented liquid diets can result in altered dietary, ileal and fecal organic matter, protein, fat, carbohydrate, and non-starch polysaccharide residue fractions.;In the second experiment, pigs were fed basal diets with increasing levels (0 to 12%) of supplemental SH. Under these feeding conditions, DM, GE, and nitrogen (N) intake and fecal N output were linearly increased with increasing SH, while DE tended to linearly decrease with increasing SH. Growing pigs fed the 3 and 6% supplemental SH diets had reduced urinary N output compared to the control fed pigs, however pigs fed 12% SH had an increased amount of urinary N. There was a tendency for the amount of N retained as a percentage of N consumed to increase in pigs fed 3 and 6% SH and decrease with 12% SH compared to control fed pigs. A similar pattern was documented for increased N retained as a percentage of N absorbed in pigs fed the 3 and 6% SH and decreased with 12% SH compared to control fed pigs. Although there were differences in N balance measures, feeding supplemental SH did not have an impact on ileal or total N digestibility. Dietary starch was nearly digested by the terminal ileum in pigs regardless of the level of SH supplementation. Although ileal and fecal NSP digestibilities are presented in Chapter III, their validity should be evaluated carefully as repeatable and accurate values were difficult to obtain.;In the third experiment, active glucose transport was increased in nursery pigs fed diets containing 6% SH compared to those pigs fed 0 and 3% SH, whereas pigs fed the 12% SH diet had intermediate glucose transport. There was a linear decrease in ileal crypt depth as the amount of SH in the diet increased from 0 to12%. However, jejunal and ileal villus and the villus:crypt depth ratio was similar among treatment groups. The level of disaccharidase activity was also similar among pigs fed varying levels of dietary fiber. These research studies indicate the potential of varying effects of dietary fiber and the process of diet fermentation to impact nutrient digestibility and gut physiology of the swine gastrointestinal tract. Factors causing the variation in response from dietary fiber are the inclusion level in the pig's diet, source of fiber in the diet, age of the pig being fed, and site of nutrient digestion and utilization within the pig.