The Role of Fibre in Pet Foods
My-Dog.info > Dogs, Diet & Food
Although not often considered by consumers as an essential
ingredient of a balanced pet food, the role of fibre is both
complex and important.
The term "fibre" which appears on a pet food label
refers to "crude fibre" (defined as that portion of a
diet which is not soluble in either hot alkali or acid). However,
it is ofttimes easier to think of fibre as either insoluble and
relatively inert (e.g. cellulose) or soluble (e.g. pectins,
carrageenan and other gums) in water. Ingredients commonly found
in dry per foods, which are high in soluble fibre, would include
oats and oat bran, whereas insoluble fibre is commonly associated
with the cereal grains such as wheat and wheat bran. Typical
crude fibre levels in pet foods range from 2.5 - 5% and can vary
as high as 24% in some specialized therapeutic foods. Levels
below 2.5% would likely imped normal bowel function.
C.V.M.A.’s recommended levels of fibre for optimum nutrition
in a healthy pet vary between 3.5% and 6.0%.
Fibre serves many functions in a diet. One important role is
the absorption of water with soluble fibre having a greater
capacity than insoluble. Fibre also acts as a bulking agent, both
on its own and in conjunction with its water holding capacity,
which increases muscle tone and movement in the large intestine
(colon) with the presumption of healthier tissue. Consequently,
fibre may be helpful in the resolution of constipation in some
pets by increasing faecal mass and by softening stool through
increased water absorption and retention.
Traditional thinking allowed that dietary fibre had no
nutritional value. However, research in dogs has shown that,
through the process of fermentation in the colon, soluble fibre
can, to varying degrees, provide a source of metabolizable
energy. In addition to energy, this fermentation produces a
variety of short chain fatty acids (SCFA) which may play a role
in the treatment of inflammatory bowel disease. SCFAs also lower
the pH of the fluid within the large intestine, thus minimizing
certain bacterial overgrowths, such as Salmonella, and minimizing
the uptake of ammonia through the cells of the colon.
It is important to appreciate that many of the properties
associated with fibre have been based upon work done in humans
and rats. The inclination to draw inter-species conclusions may
be unreliable, as there are significant differences involved. For
example, there are claims that excessive fibre levels potentially
compromise the availability to the body of certain
micronutrients, such as zinc, calcium and iron. Yet some studies
have contradictory conclusions and the implications for pet foods
have been largely uninvestigated. Research in dogs has shown
cellulose tolerance levels of 10 - 15% of the diet without any
adverse effects on the digestion of nutrients. However, fibre can
tie up the availability of the amino acid taurine in cats, which
may suggest the need for a higher dietary taurine content in cats
on high fibre diets.
Studies on humans have implicated fibre as compromising the
activity of digestive enzymes produced by the pancreas, although
fibre appears not to impair enzyme secretion. While research in
dogs is limited, at this time, high fibre diets are considered
inappropriate for dogs who have a poor ability to produce
pancreatic digestive enzymes.
Fibre affects the transit time of food through the
gastrointestinal tract, although the impact varies with fibre
type. The use of higher than normal fibre content in the diets of
diabetic cats is based, in part, upon the assumption that, by
utilizing a fibre source that adds bulk to the food and increases
retention time within the intestine, the result will lead to
lower peaking of blood sugar levels after eating a meal. Again,
such assumptions are based largely upon human research and the
effectiveness in human diabetics is coming under greater
scrutiny.
High fibre, low caloric density pet foods have been
traditionally advocated for use in weight reduction programs
based upon the principle of low caloric intakes and the feeling
of fullness achieved by the bulk of fibre physically bloating the
stomach. However, the resultant faecal mass achieved from some
very high fibre diets can severely compromise owner compliance in
the feeding of such diets.
For many pets, a diet with greater emphasis on restricted
caloric density levels and less on insoluble fibre levels may be
more successful in achieving the long term goal of weight
reduction.
Reprinted with permission from www.animalhealthcare.ca
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