Feed International - August 2017 - 19
FeedInternational ❙ 19
forms, such as acid detergent fiber and neutral detergent
fiber, offer a more inclusive methodology in terms of fiber
quantity in any specific ingredient, but they still fail to provide any qualitative trait.
Fiber is not just an anti-nutrient
There is no doubt that excess fiber will reduce
overall nutrient digestibility, as has been demonstrated by many older studies. But not all fibers act in
this way. For example, pectins form a gel that is expected to reduce iron absorption, but studies have shown
it actually enhances it. This is because water-soluble
fibers reduce transit time, enabling better digestibility.
This is, of course, true up to a certain concentration,
as we know very well that excess soluble fibers, such
as those from wheat and barley, might actually reduce
digestible enzyme access to nutrients.
There is a need to qualify
fiber in biological terms
In practical terms, gut microflora respond to two
types/functions of fiber: solubility and fermentability.
Some fibers can be partially soluble (hemicelluloses) or
partially fermentable (cellulose). We cannot provide an
easy method of characterizing each fiber based on its
chemical nature alone. Thus, each ingredient, with a very
complex fiber profile, must be assayed and characterized
individually - a very laborious and expensive proposition, but one without a more practical alternative.
Animal requirements in terms
of fiber functionality differ
In older animals, (insoluble) fiber is beneficial
August/September 2017 ❙ www.WATTAgNet.com
only in terms of gut motility, whereas its contribution to
overall energy supply is but limited (fermentable fiber).
In young animals, however, things become quite complicated. Soluble fiber is required to slow down digesta
passage rate in the small intestine, under certain conditions, whereas a healthy fermentation pattern in the large
intestine is required to ensure overall gut health. As such,
the right mix of soluble versus insoluble fiber requires
quantification for each species and age, something extremely difficult, especially considering that such ratio
is bound to be different in relatively healthy versus unhealthy animals.
Human nutrition is more
advanced in terms of fiber
There is a considerable body of literature in the
realm of human nutrition pertaining to fiber that remains
unknown to animal nutritionists. Given the close proximity of the human digestive system, similar problems of gut
health and not so disparate ingredients, or at least types
of fibers we consume, it is logical to assume that research
from human nutrition science could be used at least as the
springboard to enhance our understanding in fiber and
health interactions. After all, Hippocrates of Kos, the father
of modern Western medicine, used to say let food be your
medicine and medicine your food.
Learn more: The role of fiber in
monogastric animal nutrition,
from fiber concentration
We must move away from crude fiber and focus on
fiber solubility and fermentability. Considerable research
is required to qualify the effects of each type of fiber and
their correct ratio under each stress condition for each
animal species. Ingredients must also be characterized
according to their functional fiber concentrations. Fiber is
neither "good" nor "bad" as there are numerous types of
fibers, each with a specific role to play - something that
changes according to animal age and condition. ■