Hello everyone. My name is Diego Rodriguez, I am a research specialist at the Stein
Monogastric Nutrition Laboratory, and today, I will share data about digestibility values
of soybean meal and soybean expeller when fed to growing pigs.

Oilseed production around the world had been increased for the last century. About 575
million metric tons of oilseed are produced every year, and about 60% of the oilseed
production are soybeans, having Brazil and the United States as the biggest producers with
about 50% of the total oilseed production. Also, it’s been reported that about 239 million
metric tons of soybean meal are produced, and this soybean meal is mainly used in the
formulation of diets for monogastric animals; especially they are used in poultry diets,
but also in swine industry. And that is because of the great source of protein that can be
found in soybean meal.

There are two mechanisms that are usually used for oil extraction from soybeans. Solvent
extraction is the mechanism more used, and there is mechanical or expeller extraction.
Usually for solvent extraction, they use a chemical named hexane and also use high
temperature that facilitate the oil extraction. And therefore, the meal fraction from this
process has a lower oil content compared with mechanical pressing. Also, there is a
concern about the use of chemicals during the processing of feed ingredients. And
therefore, the soybean oil that is obtained by mechanical pressing may have a greater
value on the food market compared with the soybean oil that is obtained by solvent
extraction. It is important also to mention that solvent extraction cannot be done in a
small scale compared with mechanical extraction, and this is more important for small
producers of soybeans.

Knowing this process, Insta-Pro International developed a mechanism that is named
high-shear dry extrusion. And this process consists that the soybean is exposed to high
temperature, high pressure, high shear in a relatively short time, and this
high-temperature short-time process, it is believed to help in the rupture of plant cell
walls to facilitate the oil extraction from the soybean. But also, because of the high
temperature that is used during this process, it may help in the deactivation of
anti-nutritional factors such as trypsin inhibitors. 

After the high-shear dry extrusion process, the meal fraction from this process is
mechanically pressed, and therefore the end product will have a high-value soybean oil
that can be sold in the food market with a greater price, and also an expelled soybean
meal fraction that could be used in the formulation of diets for monogastric animals.

Therefore, the objective of this study was to test the hypothesis that including soybean
expeller to diets fed to growing pigs will increase the standardized ileal digestibility
of amino acids, also the apparent total tract digestibility of gross energy and total
dietary fiber, and also an increase of concentration of energy compared with conventional
solvent-extracted soybean meal.

To test this hypothesis, we conducted two experiments. The first experiment was to
determine the amino acid digestibility. And for this experiment, we utilized three diets.
The first experimental diet was a cornstarch with 35% of soybean expeller, and the second
was cornstarch and 33% of soybean meal as the only source of amino acid. For the diet with
soybean meal, we’d include 2% of soybean oil, and that is because it’s reported that oil
has a positive effect on amino acid digestibility. And because soybean expeller has a
greater oil content compared with soybean meal, we wanted to have similar oil
concentration in both diets to see a better effect on amino acid digestibility. In our
second experiment, we formulated three diets: a corn basal diet, plus two additional diets
including corn and 32% of soybean expeller or corn and 30% of soybean meal.

For the experimental design, for the amino acid digestibility experiment, we utilized nine
cannulated barrows with initial body weight of 56 kg, and we allotted those pigs in a
triplicate 3x3 Latin square design and therefore, we had nine pigs per diet. For our
second experiment, we utilized 24 growing barrows with initial body weight of 45 kg, and
these 24 barrows were allotted to the three experimental diets by using a randomized
complete block design. And therefore, we had eight replicate pigs per diet.

For the sample collection, for amino acid digestibility experiment, pigs were fed the
experimental diets for a total of seven days, having the initial five days as adaptation
period followed by two days of ileal digesta sample collections. And for the energy and
nutrient digestibility experiment, pigs were fed the experimental diets for nine days,
having the initial five days as adaptation period to the diet, followed by four days of
total but separate urine and fecal collection.

Jumping into the results, first, let me set up the slides. In orange color, soybean
expeller will be represented, and in dark blue color, soybean meal will be represented. As
was expected, acid-hydrolyzed ether extract was greater in soybean expeller compared with
soybean meal, and this result was expected because of the high oil content that is
observed after pressing the soybean compared with solvent extraction. In terms of crude
protein, we observed that the values of both soybeans are around 45-46%, which is a little
bit lower compared with reported values such as the NRC 2012.In terms of fiber, insoluble
and soluble dietary fiber was similar concentration between soybean expeller and soybean
meal. In terms of gross energy, because of the high acid-hydrolyzed ether extract in
soybean expeller, it was expected that the gross energy was greater in soybean expeller
compared with soybean meal.

Trypsin inhibitor is an antinutritional factor that is commonly found in soybean products,
and this has a negative effect on amino acid digestibility. A way to ameliorate the
negative effects of trypsin inhibitor is by using heat treatments. And after the heat
process that is commonly used for soybean expeller and soybean meal, there was a reduction
in trypsin inhibitors in both soybean products, having a greater reduction in soybean meal
compared with soybean expeller. Also, it’s been reported that values close to 4 units/mg
of trypsin inhibitors are enough to have no effects on amino acid digestibility.

Therefore, we analyzed the standardized ileal digestibility of amino acid, and we found
out that soybean expeller has greater standardized ileal digestibility of amino acid
compared with soybean meal—with the exception of lysine and tryptophan, that tended to be
greater in soybean expeller compared with soybean meal. This effect is likely because of a
positive effect during the dry extrusion process that allows a better utilization of the
protein from soybean expeller compared with soybean meal.

In terms of apparent total tract digestibility of gross energy, there was no difference
among soybean products and corn. However, the apparent total tract digestibility of total
dietary fiber was greater in soybean expeller compared with corn. And this effect may be
explained because of a greater soluble dietary fiber concentration in soybean products
compared with corn. On the other hand, there was no difference in total dietary fiber
digestibility between soybean expeller and soybean meal.

In terms of energy concentration, soybean expeller has a greater digestible energy
compared with soybean meal and corn. And the same was observed for metabolizable energy,
where soybean meal and corn had lower ME compared with soybean expeller. The reason of
this result is likely because of a greater oil content in soybean expeller compared with
soybean meal and corn, and it is known that fat produces more energy and less heat
production compared with starch and proteins.

Based on the metabolizable energy values and nutrient composition of the feed ingredients,
we calculated the net energy of the feed ingredients using the prediction equation from
Noblet. And it was observed that soybean meal has the lower net energy compared with
soybean expeller and corn. However, there was no difference between soybean expeller and
corn in net energy.

Based on the energy values, we calculated the metabolizability of energy to estimate how
much of the energy was utilized for the pig. And it was observed that the ME to DE ratio
in corn was greater compared with soybean meal. And this result may be explained because
of the high concentration of crude protein in soybean meal compared with corn. And it is
known that the efficiency of utilization of energy in proteins is the lowest compared with
starch or fat. However, there was no difference in ME to DE ratio between soybean expeller
and corn. On the other hand, corn has the greatest NE to ME ratio, compared with the
soybean products, and this effect can be also explained because of the higher crude
protein concentration in soybean products compared with corn. However, this observation is
also telling us that the soybean expeller has a better utilization of energy compared with
soybean meal.

So now, let’s move on into the conclusion of this study. Based on the result of this
study, soybean expeller had less crude protein concentration and a higher oil
concentration compared with conventional soybean meal. By having that nutrient composition
and based on the results of this experiment, we can conclude that soybean expeller has a
greater standardized ileal digestibility of most of the amino acids compared with soybean
meal, but the digestibility of fiber was not different between the two soybean products.
In terms of energy concentration, metabolizable energy and net energy were greater in
soybean expellers compared with soybean meal.

And with that, I would like to thank Insta-Pro International for the financial support and
also all the members from the Stein Monogastric Nutrition Laboratory. And if you want more
information about all the work that is done in our lab, you can visit our website at
nutrition.ansci.illinois.edu.