WHAT is fibre? It is naturally
found within plants (often as
structural components), and it is
resistant to digestion by the
enzymes secreted within non-
ruminant, monogastric
animals.
Instead, the
majority of
fibres are
fermented
by micro-
organisms
within the colon into short-chain
fatty acids (SCFAs).
Some of the most common fibres
include cellulose (and hemicellulose),
gums and mucilages. In addition to
this, other plant polysaccharides can
also be considered as fibres – these
include fructans (e.g. inulin, which
contains fructo-oligosaccharides) and mannans.
Fibres can be classified by their structure, rate of fermentation,
solubility in water, digestible and
indigestible fractions, water-holding capacity and viscosity. Most rapidly
fermentable fibres (such as fructo-
oligosaccharides) are soluble,
whereas slowly fermentable fibres
(such as cellulose) tend to be
insoluble.
The general effects of soluble
fibres include:
- delaying gastric
emptying; - the slowing of colonic
transit; - a decrease in colonic pH;
- and
the fermentation to SCFAs providing
energy for colonocytes.
Conversely, insoluble fibres may
hasten gastric emptying; they have no
effect on, or hastening of, colonic
transit; and they may result in an
increase in faecal bulk. Efforts to
increase faecal bulk have been
recommended for the management
of irritable bowel syndrome (IBS)
and other gastrointestinal disorders.
Commonly used fibres
Examples of commonly used fibres
include:
- Cellulose – which consists of glucose
units bound together by β1,4-linkages
(rather than the α-linkages in starch).
The β1,4-linkages can only be broken
apart by microbial enzymes, and this
results in cellulose being fermented in
the colon by micro-organisms.
Cellulose is an effective stool bulking
agent. - Psyllium – this is a good source of
soluble fibre. The seed husks contain
glycosides and mucilages which swell
when in contact with fluid, forming a
gel-like substance. Psyllium can help to
improve faecal consistency and for this
reason it is often useful for the
nutritional management of animals
with large intestinal problems. - Fructo-oligosaccharides (FOS) – this
is able to enter the colon intact because
it is not digested by enzymes in the
small intestine. In the colon, certain
beneficial bacteria (bifidobacteria and
Lactobacillus spp.)
ferment FOS readily,
which leads to an
increase in their
numbers. The resulting
reduction in intestinal
pH can minimise the
growth of pathogenic
bacteria such as E. coli
and Salmonella.
Benefits
The main function of insoluble fibre is
to increase faecal bulk and the level of
water in intestinal contents.1 Fibre has
been shown to shorten intestinal transit
rate in dogs with normal or slow transit
time and to prolong transit rate in dogs
with rapid transit time.1 These factors
help to promote and regulate normal
colonic motility and faecal consistency.
Soluble fibre is rapidly fermented
by micro-organisms within the colon
into SCFAs (acetate, propionate and
butyrate). Colonocytes preferentially
use butyrate as their source of energy,
rather than obtaining energy from
glucose or amino acids.1 In addition,
SCFAs facilitate the reabsorption of
sodium, chloride and water in the
colon.
Finally, the production of SCFAs
lowers the pH of the colonic contents,
which can result in decreased numbers
of pathogenic bacteria and an
increased colonisation resistance
against pathogenic bacteria.1 As can be
seen, SCFAs (in particular butyrate) are
vital for the health of the colon.
Fermentable fibres that can
stimulate the growth of intestinal
bacteria, such as lactobacilli and
bifidobacteria, are often called prebiotics. Prebiotics have been shown
to limit the growth of intestinal
pathogens.
The addition of fibre may not be
suitable for every animal with small
intestinal disease due to the potentially
abrasive properties of certain fibres
and so it is important to evaluate each
patient’s needs on a case by case basis.
Specific conditions
Fibre can assist in the nutritional
management of pets with the following
specific issues:
- Diarrhoea and constipation
Fibre can normalise intestinal water
content by absorbing water from the
luminal contents if an animal has
diarrhoea and adding moisture to the
faecal matter in animals with
constipation. The addition of
fermentable fibre (psyllium and FOS)
within the diet of dogs and cats with
constipation is recommended, since the
gas produced by the fermentation of
these fibres can help to break up the faecal mass. Psyllium is
also able to absorb
water which increases
the volume of the
faeces. The softer
stools that are created
are then easier to pass. - Colitis Increasing the amount of fibre in a diet can
help to bind bile acids and prevent them being deconjugated by bacteria.
Deconjugated bile acids are toxic to the
colonic mucosa and they can also
increase permeability and fluid
secretion in the colon as well as
stimulating mucus output.1 The
addition of insoluble fibre can help to
bind water, producing better formed,
softer faeces. This leads to stretching of
the colonic smooth muscle, helping to
restore normal peristalsis and reduce
straining. - Obesity
The addition of fibre to a pet’s diet can
be effective for controlling body weight
and managing obesity. A carefully
balanced level of soluble and insoluble
fibre in the diet can increase bulk in the
stomach and intestines and helps to
promote the feeling of satiety whilst
fewer calories are consumed.1
In conclusion, although fibre is not
considered an essential component in
the diets of dogs and cats, the use of
fibre as an aid in the nutritional
management of pets with various GI
issues is gaining much interest.
Undoubtedly, this interest will continue
to increase in the future.
- References on file. For more details,
visit vetportal.royalcanin.co.uk (or
vetportal.royalcanin.ie for Ireland).
