Dietary Fiber

goal for dietary fiber in diet

cats: 5-20% (carnivores)

most animals: 55-60% of energy from CHOs

dietary fiber

measure of nonstarch polysaccharides, lignin, resistant starches

definition - nondigestible CHO and lignin that are intact and intrinsic in plants

includes

• cellulose, lignin, hemicellulose (plant cell wall)

• pectins, gums (secreted in response to plant injury)

• mucilages (associated w plant wall)

**complex nonstarch polysaccharides, lignin is exception

dietary fiber definition

chemical - sum of allnon-starch polysaccharides (NSP), non-digestible oligosaccharides, and lignin

physiological - all plant polysaccharides and lignin that are resistant to hydrolysis by endogenous secretions of the GI tract

dietary fiber in canine/feline nutrition

portion of edible parts of plants or analogosus carbohydrates that are resistant to digestion and absorption in the SI of animals

consists of

• polysaccharides (cellulose, hemicellulose, pectins) 10+ subunits

• oligosaccharides (inulin, raffinose) 3-9 subunits

• lignin

• associated plant substances (partially/fully fermented in LI)

B(1-4) linkages of cellulose are resistant to endogenous enzymes

a(1-4) linkages of starch are digested by endogenous enzymes

how fiber composition change with processing and source

Starch

storage carbohydrate, NOT a dietary fiber

concentration varies widely in feed ingredients

resistant starch (white beans, lentils, plantains)

• not fully digested in SI

• grouped within total dietary fiber and can provide health benefits similar to those of soluble fiber

oligosaccharides

found in plant cell wall, plasma membrane, vacuoles, of beans, lentils, whole grains

non-digestible by mammalian enzymes

fructooligosaccharides = prebiotics

cell wall (soluble fibers)

primarily found in the cell walls of oats and barley

beta-glucans, pectins, gums

resistant to mammalian enzymes, fermentable, viscous

cell wall (insoluble fibers)

cellulose - structural homopolysaccharide, glucose units, B-1-4-glycosidic bonds, resistant to mammalian enzymes, partially fermentable in LI

hemicellulose - structural heteropolysaccharide, resistant to mammalian enzymes, partially fermentable in LI

lignin

complex structural organic polymer

resistant to mammalian enzymes

non-fermentable by bacteria

present in all vascular plants

considered the greatest impediment to digestion

phenolics

present in many plants - defensive mechanism

antinutritive properties (interferes with digestion)

antioxidant activity

soluble dietary fiber

pectins, gums, mucilages, beta-glucans, some hemicellulose

increased water holding capacity (hydrophillic

delay gastric emptying, slow intestinal transit, and delays glu uptake (slows things down)

modifies microbiome

tends to be fermentable/rate of fermentability varies

insoluble dietary fibers

cellulose, some hemicelluloses, lignin

decreased water holding capacity (hydrophobic)

increases fecal bulk

decrease transit time (speed things up) - impedes glu absorption, hydrolysis of starch

decreases energy density of diet, increases post-prandial satiety

fermentability decreased

modes of action of soluble fibers on gut health

fermentation by gut microbiota produces short chain fatty acids (SCFA, VFA) → fuel for cells, lower pH, promote growth of beneficial microbes

regulation of bowel movements → stool consistency, manage diarrhea

enhance nutrient absorption → slow digestion/absorption

enhance barrier function/gut integrity → anti-inflammatory properties, enhance tight junctions

modes of action of insoluble fiber on gut health

increase passage rate, decrease pathogen proliferation and adhesion

decrease E. coli and diarrhea incidence

increase fecal bulk (regular bowel movements)

enhance satiety

SCFA production in large intestine/colon

other effects of fiber

growth performance

• DF reduces energy intake via nutrient dilution

• small quantities may improve but depends on source, animal species, age, environment

weight control

• used to restrict nutrient digestion/absorption, energy intake

• fiber dilutes caloric content

glycemic index

• viscous fibers in SI act as a barrier to release of nutrients and slow absorption (control glu/insulin metab)

satiety

• gastric distention

• work/time for chewing

  • hormonal (leptin —| hunger vs ghrelin → hunger

fiber for cats

obligate carnivores, require more fat/protein than fiber

recommendation - no specific minimum, often included at 1.5-4% DM basis

support digestive health, prevent constipation, and manage conditions (obesity, hairballs)

fiber for dogs

omnivores - can tolerate and benefit from more fiber in their diets

recommendation - included in diets at 2.5-5%, may be higher in therapeutic diets

support GI health, healthy weight management, useful in dogs with diabetes/digestive disorders