Salivary Amylase
Form of Dietary CHO
Starch Maltose Sucrose Lactose
Stomach
(amylase from saliva)
Dextrin→Maltose
Small Intestine Pancreatic Amylase
Maltose
Large Intestine
Miller et al. (eds.), 1991
Digestion in Large Intestine
Carnivores and omnivores
▪ Limited anaerobic fermentation ▪ Bacteria produce small quantities of cellulase ▪ Volatile fatty acid (VFA) produced by microbial digestion of fibers
➢ Pancreatic amylase ▪ Hydrolyzes alpha 1-4 linkages ▪ Produces monosaccharides, disaccharides, and polysaccharides ▪ Major importance in hydrolyzing starch and glycogen to maltose
Summary of Carbohydrate Digestion and Absorption in
Monogastrics
Consist of starches, glycogen, sucrose, lactose, glucose, fructose
Maltose
Maltase
Glucose + Glucose
Lactose Lactase
Glucose + Galactose
* Poultry do not have lactase
Digestion of Disaccharides
Newborns have a full complement of brush-border enzymes
Polysaccharides
Amylase
Disaccharides
Digestion in Small Intestine
Digestion mediated by enzymes synthesized by cells lining the small intestine (brush border)
With exception of newborn animal (first 24 hours), no di-, tri-, or polysaccharides are absorbed
Monosaccharides absorbed primarily in duodenum and jejunum
Nutrient Absorption - Carbohydrate
Active transport for glucose and galactose
Sodium-glucose transporter 1 (SGLT1) Dependent on Na/K ATPase pump
Facilitated transport for fructose
Brush Border Enzymes
Glucose Fructose Galactose
+
+
+
Glucose Glucose Glucose
None
Bacterial Microflora Ferment Cellulose
Carbohydrate Absorption in Monogastrics
Brush Border Enzymes
Disaccharides
Monosaccharides
* Exception is β-1,4 bonds in cellulose
Digestion in Small Intestine
Sucrose
Sucrase
Glucose + Fructose
* Ruminants do not have sucrase
of the short time food is in the mouth ▪ Ruminants do not have this enzyme ▪ Not all monogastrics secrete it in saliva
Carbohydrate Digestion
Pancreas
Carbohydrate Digestion
Non-Ruminant Carbohydrate Digestion
Mouth
➢ Salivary amylase
▪ Breaks starches down to maltose ▪ Plays only a small role in breakdown because
▪ Little absorption in stomach and large intestine
Small Intestine Carbohydrates
Monosaccharides
Portal Vein
Active Transport
Liver
Distributed to tissue through circulation
▪ Propionate ▪ Butyrate ▪ Acetate
Digestion in Large Intestine
Post-gastric fermenters (horse and rabbit)
▪ Can utilize large quantities of cellulose ▪ Cecum and colon contain bacteria which
produce cellulase ▪ Cellulase is capable of hydrta-glucoside linkage
Overview Monogastric Carbohydrate Digestion
Location
Mouth
Enzymes