Starch and fiber properties affect their kinetics of digestion and thereby digestive physiology in pigs

Abstract

Traditionally in swine nutrition, analyses of starch and fiber have focused on assessing quantity; however, both have a wide range of functional properties making them underappreciated nutrients. Starch ranging from low to high amylose changes from rapidly digestible in the upper gut to poorly digestible but fermentable in the lower gut thereby changing from a source of glucose to VFA source. Likewise, fibers ranging from low to high viscosity affect digesta flow and from slowly to rapidly fermentable alter production of VFA serving as energy for the gut or whole body. Our hypothesis is that total extent, kinetics, and site of digestion or fermentation of starch and fiber are important for whole body nutrient use and intestinal health. To elucidate their effects, we developed in vitro, lab-based methodologies to describe kinetics of digestion and fermentation and linked these with in vivo models including i) ileum cannulation to collect digesta, ii) portal-vein catheterization to sequentially sample blood, iii) slaughter method to collect site-specific intestinal tissue and digesta, and iv) indirect calorimetry. Using these methods, kinetics of nutrient absorption was associated with pancreatic and intestinal hormones released into the portal vein, intestinal microbiota, and gene expression in intestinal tissue and microbiota. These studies confirmed that slowly digestible starch is partially degraded in the distal small and large intestine and fermented into VFA including butyrate (10-fold increase in net portal appearance), which reduces insulin responses by 60% and whole body energy use. Starch entering the distal intestine altered mRNA abundance of nutrient transporters and was bifidogenic. Extremely viscous purified fiber dampened glycemic responses and reduced digesta passage rate by 50% thereby increasing ileal digestion of dietary nutrients whereas increased fiber in feed grains reduced nutrient digestibility. Fermentable fiber increased butyrate and insulin production. These methods will therefore support elucidation of mechanisms that link starch and fiber properties to whole body nutrient use and intestinal health.

Acute effects of pea protein and hull fibre alone and combined on blood glucose, appetite, and food intake in healthy young men – a randomized crossover trial

“…Dietary fibre, especially viscous fibre, slows gastric emptying, the rate of flow through the small intestine, and the rate of nutrient absorption (Jenkins et al 1978;Ray et al 1983;Blackburn et al 1984;Meyer et al 1988;Bergmann et al 1992;Benini et al 1995;Leterme et al 1998;Marciani et al 2000;Kristensen et al 2011;Zijlstra et al 2012;Scazzina et al 2013). Pea hulls contain mainly cellulose (Reichert 1981), an insoluble fibre, but also contain pectins, glucans, arabinans, and hemicelluloses (Weightman et al 1994;Renard et al 1997).…”

Effects of alginate and resistant starch on feeding patterns, behaviour and performance in ad libitum-fed growing pigs

“…Thus, in spite of the reduced glucose supply from enzymatic digestion directly after the meal, RS provides a large amount of SCFA to be oxidized in the postabsorptive phase (Haenen et al, 2013;Souza da Silva et al, 2014). According to Zijlstra et al (2012), absorbed SCFA are metabolized in various cell types, including colonocytes, hepatocytes, and skeletal and cardiac muscle cells. A prolonged energy supply from SCFA throughout the day may have reduced the mobilization of glucose from cell storage and likely led to a more efficient mechanism for maintenance of blood glucose between meals in pigs fed RS-containing diets.…”

Diet nutrient digestibility and growth performance of weaned pigs fed field pea

“…Thus, starch in field pea is not digested completely in the small intestine and up to 20% of starch is fermented in the large intestine of pigs (Wiseman, 2006). However, starch fermentation instead of starch digestion is less efficient energetically for the pig (Zijlstra et al, 2012).…”