Modulation Of Intestinal Cell Differentiation By Different Fiber Sources And Evaluation Of Using A Modified Three-Step Procedure To Predict Digestible And Metabolizable Energy Content In Growing Pigs

Abstract

Accurate swine diet formulation is essential for optimizing caloric and nutritional efficiency of pork production. The large variability in energy and nutrient composition among high fiber ingredients from different sources requires the development and use of relatively rapid, inexpensive, and accurate methods to determine dynamic estimates of these ingredients. The overall goal of this thesis was to develop a better understanding of the potential value of using a 3-step in vitro digestibility system to obtain dynamic estimates of energy and nutrient digestibility, and determine the physiological effects of feeding high fiber ingredients to pigs. Specifically, the objectives were: 1) investigate the mechanisms of how high fiber ingredients affect nutrient utilization in swine by understanding how dietary fiber affects gastrointestinal physiology, specifically cell proliferation and differentiation of the small intestine, and 2) to develop and evaluate a modified three-step in vitro method for rapid estimation of the digestible and metabolizable energy content and fiber digestibility and fermentability among high fiber feed ingredients. To achieve these objectives, we conducted 4 studies. Chapter 2 describes the effects of different fiber source in the diet on modulation of intestinal cell differentiation in growing pigs. The results showed feeding diets containing what straw (WS) and corn distillers’ dried grains with solubles (DDGS) modulated intestinal differentiation by promoting goblet cells and altered expression of nutrient receptors and transporters in growing pigs, while feeding soybean hulls (SBH) had less effect. Chapter 3 describes differences of in vitro hydrolysis, fermentation, and estimated energy among and within high fiber ingredients using a modified three-step procedure in growing pigs. The results showed that this procedure was useful for detecting the variability of dry matter (DM) digestibility among and between WS, SBH, and corn DDGS sources. Chapter 4 involved evaluating the use of in vitro DM digestibility and gas production to predict apparent total tract digestibility (ATTD) of total dietary fiber (TDF) for growing pigs. Chapter 5 investigated prediction of digestible energy (DE) and metabolizable energy (ME) of DDGS for growing pigs from in vitro digestible nutrients. The results showed that in vivo digestible neutral detergent fiber (NDF), DM, and ether extract (EE) are the best predictors for DE and ME content of corn DDGS fed to growing pigs. Overall, the results from these 4 studies showed that WS, SBH, and corn DDGS 1) regulate intestinal cell differentiation differently, 2) have different fermentability, and 3) can be utilized by a modified three-step procedure and gas production technique to provide an accurate prediction of ATTD of TDF, and potentially, DE and ME content for growing pigs. However, further refinements are needed to improve the practical application of this procedure in evaluating high fiber ingredients.