Background on Further Processing for Animal & Industrial Use
Background
Soybean meal (SBM) for animal use
(77%) dominated the domestic and international
use of the 2008/09 US soy harvest of nearly 82
million metric tons, followed by human food
products (20%) and industrial uses such as
biofuels (3%).
About half of SBM contains a high
amount of protein with a complimentary balance
of amino acids similar to corn, making it a good
protein source. However, 35% of SBM consists
of carbohydrate which is ineffectively utilized
by poultry and swine. As a result, additional use
and value of soy by the livestock industries will
likely come from maximizing nutritional value
for the animal.
Limitations to Value Realization
To gain potential value and further use
of soy, we must look at industry specific issues.
For this paper, we’ll focus on poultry and swine,
recognizing that there are many other avenues to
realizing value in the processing portion of the
value web.
Poultry: Very little of the carbohydrate
in SBM can be digested by the bird. This
indigestibility is demonstrated in the
digestibility differences of feces noted in the
pictures on the right between corn and SBM
without hulls. Availability of soy phosphorus
improves with dietary supplementation from
phytase, but the digestibility of phosphorus from
SBM by poultry (& swine) is less than 50% with
enzyme supplementation.
Swine have improved digestibility of
soy’s carbohydrate fraction over poultry, but
non-starch polysaccharides can have detrimental
effects on their intestinal health. Additionally,
soy protein eaten by young pigs can cause
allergenic responses in the pig resulting in
diarrhea, intestinal inflammation, and increased
susceptibility to other enteric disease—which
reduce nutrient utilization.
Other soy products have been used
effectively in swine, including hulls as a dietary
“bulking” agent in sow gestation diets. Hulls
help with satiety as well as a fiber source to
reduce ammonia emissions through
improvement in hind-gut fermentation. Glycerin,
a biodiesel co-product, can be supplemented up
to 10% in pigs and poultry diets, however
beyond this, the liver can‘t metabolize it
effectively, and physical form of the diet beyond
10% of glycerin in the diet makes it so the diet
does not flow in storage bins.
The Dairy industry uses SBM primarily
in lactating cow rations as it provides a good
amino acid balance vs corn based co-products.
Treated SBM (heat or extruded), is used to
increase “bypass protein” (milk production
stimulant), however pricing limits further use.
Beef: As SBM is too expensive for a
practical source of protein, the hulls remain as a
potential cheap energy source for beef
cattle/calves if treatment allows for the
improved fiber digestibility.
Example of Complex Issues Affecting Value of Soy for Poultry & Swine
Problem Overview
Fiber and other non-starch
polysaccharides (fiber) in soy can have a
dramatic impact on nutrient digestibility, manure
volume and animal growth rates in poultry and
swine. Addressing these issues requires a crosscutting approach between seed genetics, further
processing and animal studies. For example, the
apparent digestibility of dry matter is only 54%
for SBM with hulls. Collectively, the inefficient
use of these non-starch polysaccharides (fiber)
accounts for 37% of the meal that cannot be
digested. If hulls are removed from the SBM,
the cellulose and total fiber content are
improved, but are still not well utilized by the
bird. Therefore, prestarter or starter diets
containing a high proportion of SBM may not
provide the amount of calculated energy and
may suppress early growth. This is a significant
issue for a chick’s first week of life when calorie
needs are high but their access to calories is
reduced 5 to 10% when fed SBM.
While it is often thought that digestion
of amino acids is adequate from soybean meal,
we know that cultivation location, season,
processing technique, and level of antinutritional factors (e.g. trypsin inhibitors, lectins,
saponins, and oligosaccharides) influence amino
acid availability to the swine and poultry. Some
of the soybean’s proteins can increase allergenic
responses in the weanling pig and this
inflammatory response leads to reduced growth
the first 14 days post-weaning.
What’s Been Done to Address Problem
A multi-disciplinary approach is
required across genetics, processing and animal
studies. (Note: if you were to look at this from a
Value Chain Analysis, you’d not see a natural
connection between these segments. It requires a
look across the soybean web to assess the
implications.)
Genetic approaches: Soy lines have
been developed to address both the
indigestibility and allergenic responses:
A) K. Rainey (Purdue –Agronomy) has
developed low oligosaccharide lines. Prior USB
funded work has demonstrated at least an eight
percent improvement in caloric use by broilers.
B) E. Herman (Univ. AR) has developed low
allergenic soy lines.
C) A. Schinckel & T. Stewart (Purdue – Animal
Sciences) have developed divergent lines of pigs
(now have 6 generations of selection) to study
the impact and mediation strategies to
hypo/hyper-allergenic responses to dietary soy.
Dietary approaches: Two particular approaches
have been developed to address the inefficient
use of soy carbohydrates by poultry and swine:
A) Enzyme use. Dr. Adeola (Animal Science)
along with collaborators have demonstrated that
as calories become more expensive in poultry
and swine diets, combinations of carbohydrases
(xylanase, α-galactosidase, cell-wall degrading
enzymes, etc.) substantially improve caloric use
by the animal. This valuation becomes
extremely important as feed ingredient prices
increase, and as soy becomes a larger part of the
diet (e.g., livestock diets without animal
protein).
B) Soy protein isolate/concentrate. Prior
research with broilers has demonstrated a 5 to
10% improvement in metabolized calories from
soy concentrate than traditional SBM. Similar
improvements have been seen by Dr. Applegate
(Animal Sciences) in early turkey diets with the
use of soy concentrate vs SBM to partially
alleviate the turkey’s immature digestive
capacity.