Pig International - November 2017 - 33
PigInternational ❙ 33
First, in animals prone to bacterial diarrheas and fed
diets without antibiotics, we require a low-moisture
environment in the upper gastrointestinal tract - otherwise excessive bacterial growth may promote pathogenic strains to the animal's detriment. But, a drier digesta will result most likely in reduced penetration by
digestive enzymes, leading to reduced nutrient digesta.
So, these two aspects work against each other, and one
cannot have both in the same feed formulation design.
Finally, we must ensure water is released in the
large intestine for reabsorption. Otherwise, we will
have incidents of wet litter, leaky diarrhea (non-pathogenic), dirty eggs, loose stool, etc. Thus, diets must be
designed having specific goals and always taking into
account the hygiene levels of each farm before employing the right tools to control digesta moisture levels at
each site of the gastrointestinal tract.
The chemical value of renown remains crude fiber,
but it is now antiquated as we understand it includes but
a small fraction of functional fibers. For example, a feed
high in pectins or highly soluble hemicelluloses is not
likely to figure high in terms of crude fiber as these fractions are not caught up easily during crude fiber analysis.
cal analyses appear more comprehensive, but they remain
largely irrelevant to monogastric nutrition. Such are NDF
and ADF analyses that were developed to cater for ruminant fiber nutrition. Even though these values will not
change from species to species, like crude fiber, we have
virtually nil data regarding monogastrics. Even, then,
modern fiber thinking is now beyond chemical analyses
as we focus more on biological values. This is not to say
chemical analyses are obsolete, but rather that they have
become a tool in establishing biological values that correspond to each species.
In monogastric animal nutrition, we are currently
describing fiber as soluble versus non-soluble (for the
part of the gut that includes the stomach and most of
the small intestine), and fermentable versus non fermentable (for the part that includes the last part of the
small intestine and all of large intestine). It is a common error to believe that all soluble (or non-soluble)
fiber is equally fermentable (or non-fermentable).
Today, we know that this is just not true, at least in
absolute terms when precision is required. It should be
noted here that in order to determine the solubility and
fermentability of an ingredient, we require live animal
tests, something that adds to the delay by which new
data emerge. In-vitro (lab) tests will eventually become
commonplace, but these will always remain more expensive than chemical analyses, and, of course, never
as accurate as in-vivo (live animal) tests. Thus, research focus remains on those species and feeds that
can provide a quick return on investment - such as
feeds for young animals, those raised with antibioticfree diets under challenging conditions and animals
already suffering from gut health problems. At this
moment, there is not a concrete set of feed specifications for these biological values, and, as such, each
nutritionist has to use empirical evidence, at best.
Learn more: 6 fiber insights for formulating livestock feed, www.WATTAgNet.com/articles/30802
November/December 2017 ❙ www.WATTAgNet.com