There is increasing evidence that dietary fiber is important
in maintaining the overall health of dogs and cats. Fiber in
petfoods plays a significant role in the prevention and
mitigation of several illnesses, including:
- Irritable bowel syndrome,
- Megacolon and
- Colon carcinoma.
Other possible clinical nutrition uses of fiber include
blunting of postprandial glycemia, preventing the growth of
pathogenic microorganisms and improving nitrogen metabolism in
pets with renal dysfunction. Although the contribution of
energy from fiber fermentation is minimal in dogs and cats,
increasing evidence indicates that this fermentation
contributes to their intestinal health.
As dogs and cats have become domesticated, their diets have
changed from being largely meat-based to ones containing a
substantial amount of carbohydrate. Indeed, many commercial dog
and cat diets contain 30% or more carbohydrate, of which
dietary fiber can be an appreciable component.
Including fiber in petfoods can impact nutrition in several
ways. Moderate to high concentrations of dietary fiber can
decrease food intake and help improve appetite regulation.
Depending on the fermentability and viscosity characteristics
of a particular dietary fiber source, fibers can slow gastric
emptying, decrease intestinal transit time and decrease total
tract nutrient digestibility (see Table 1). However, more
recent data indicate that ileal nutrient digestibility is not
compromised. Other physiological responses attributed to fiber
include fecal bulking, production of short chain fatty acids
(SCFA), enhanced colonic morphology and intestinal function and
a positive influence on the distribution of colonic microflora
(see Table 2).
An ideal dietary fiber or fiber blend should provide good
stool characteristics without significantly decreasing nutrient
The fermentation compartments of companion animals occur
posterior to the stomach. The fermentative role of the cecum is
likely more important in the dog than in the cat. The cecum is
a blind ended sac of the proximal colon in the dog whereas it
is considered a vestigial organ in the cat.
Dogs are capable of fermenting a significant quantity of
dietary fiber. Total tract digestibility of lignocellulose,
hemicellulose and cellulose of 33%, 47% and 18%, respectively,
have been reported in dogs. Swanson et al. investigated the
fermentability of several alternative fiber sources using a
canine in vitro fermentation model.
Fiber sources tested included several pomaces (apple,
carrot, grape, tomato), flaxseed, pea hulls and pistachio. On a
dry matter basis, substrates contained between 55% and 86%
total dietary fiber (TDF) and had varying rations of
insoluble:soluble fiber. Accordingly, fermentation
characteristics also varied greatly, resulting in a range of
organic matter disappearance values (9.3% to 51.7% after 24
hours of fermentation).
The carnivorous nature of cats, their relatively small colon
and their lack of a functional cecum suggest that they may not
utilize dietary fiber as extensively as do other non-ruminants.
However, Kienzle noted reduced pH values of large bowel digesta
and feces after cats ingested raw corn starch. The change in pH
was undoubtedly a result of SCFA produced from microbial
hindgut fermentation of starch.
Sunvold et al. fed domestic shorthair cats diets containing
0% or 9.5% supplemental TDF from either beet pulp (a moderately
fermentable fiber), cellulose (a nonfermentable fiber), a 3:1
cellulose:gum Arabic mixture or two different blends of
- 35% pectin + 30% locust bean gum + 20% carob bean gum +
15% guar gum or
- 60% beet pulp + 22% rice bran + 10% pectin + 8% carob
Total tract disappearance of TDF was increased by
consumption of beet pulp (38.2%) and fiber blends (50.6% and
41.1%, respectively) compared to the control diet (5.3%)
However, TDF digestibilities of cellulose (8.9% and the 3:1
cellulose:gum Arabic mixture (5.7%) were similar to the control
diet. These data refute the assumption that cats are incapable
of utilizing fermentable carbohydrates.
To further define the role of dietary fiber for companion
animals, research is needed in several areas. For example, the
role of fiber in the longevity of dogs and cats is virtually
unknown. Also, the role of fiber in diets to aid treatment of
specific disease is promising but needs further study. Finally,
although evidence exists as to the potential benefit of SCFA
production in the intestine of other species, information
regarding the role of SCFA in the dog and cat is scarce.
Development of a better knowledge base in these areas would
further refine our ability to develop diets for companion
animals that would optimized their health and well-being.
Online extra!This article is based on a 33-page paper by
Fahey et al., which includes references, and is titled The role
of dietary fiber in companion animal nutrition. It is available