| |
Soybean
Meal Composition Studies
A study was undertaken at North Carolina State University to identify
soybean meal’s nutritional characteristics desired by swine
nutritionists. Specifically, the research was designed to evaluate
compositional variation in experimental and commercial soybean varieties
and whether these compositional differences were large enough to
be nutritionally or environmentally important to the swine nutritionists.
In a study reported in 2002, the digestibility of soybean meal was
found to be relatively uniform across the U.S. and Netherlands.
This lack of variability was attributed to minimal genetic variation
in nutritional traits in commercial soybean cultivars and to uniform
meal processing conditions. This study was designed to expand these
research investigations and to evaluate experimental soybean germplasm
lines with unique traits.
Seventy-two soybean samples were analyzed for crude protein (CP),
neutral detergent fiber (NDF), acid detergent fiber (ADF) and in
vitro dry matter (DM) digestibility. Based on the variation found,
eight samples (five genetically modified lines and three commercial
varieties) were selected for testing. The eight soybean sources
were sent to the Texas A&M Oilseed Processing Laboratory to
be processed into meal using carefully controlled uniform processing
conditions. The pilot-plant solvent-extracted meals were analyzed
for moisture, crude fat, crude protein, crude fiber, ash, urease
activity, trypsin inhibitor, protein dispersibility, phytate phosphorus
and oligosaccharides using officially accepted methods.
A Latin square designed study with eight pigs and eight diets was
used for the ileal digestibility experiments. The sixteen-percent
crude protein experimental diets were formulated with soybean meal
as the only protein source. Soybean meal levels in the diets ranged
from 31-34 percent. Feed and freeze-dried ileal digesta were analyzed
for the chromic oxide marker, amino acids and dry matter.
In another experiment, the total track digestion was determined
using five soybean meals, ten crossbred barrows and a 5x5 Latin
square designed study. Urine and feces were collected, stored and
evaluated for gross energy, nitrogen and odor characteristics. Using
data from the two trials, the researchers calculated fermentation
rates for CP and DM based on actual ileal digestibilities of the
feed ingredients and total tract digestibilities of the complete
diet.
Results indicated that the 72 soybean samples was fairly uniform;
the coefficients of variation (CV) for CP, NDF and ADF were 3.6,
7.4 and 8.8%, respectively. However, the researchers were successful
in selecting eight soybean samples with a higher CV for ADF (26%),
but were not successful increasing the CV for CP (3.7%). The ranges
of values were: CP, 48.2-53.1%; CF, 2.6-5.6%; NDF, 5.8-9.2%, ADF,
2.6-5.0%; hemicellulose, 3.1-4.7%; raffinosis, 0.15-1.22% and stachyose,
0.28-5.93%. These data suggest that important composition differences
exist between different soybean germplasm lines. These differences
may have an impact on the meal’s nutritional value. These
results also indicate that the variations in protein levels in soybean
lines are relatively small and processing does not increase the
amount of variation in the meal produced.
Several correlations were found between the meal components. The
CP content of the meal was negatively correlated with fiber (r=
-0.70, P=0.05), raffinose (r= -0.90, P<0.01), and stachyose (r=
-0.96, P<0.01). Trypsin inhibitor, urease value and protein dispersion
index were all correlated (r= -0.63 to -0.83) indicating processing
had a similar effect on all of these meal components.
The researchers reported differences up to 6% in ileal DM digestibilities
and 8% in ileal CP digestibilities. These differences were reduced
to 1.1% for total tract DM digestibility and 4% for total tract
CP digestibilities by further break down of the materials in the
lower digestive track. Ileal digestibilities of the eight soybean
meals ranged from 79.6 to 83.2% and were highly correlated with
energy digestibility (r= 0.91, P<0.05). Crude protein ileal digestibilities
ranged from 80.6 to 84.6% and were not correlated with DM digestibility.
It should be noted that the apparent ileal digestibilities for CP
and lysine, methionine and threonine were highly correlated (r>0.96,
P<0.01). Protein dispersibility index, trypsin inhibitor and
urease levels had little impact on digestibilities in this study.
|
|
|
  |
Turn Page |
PRINTABLE
TEXT VERSION |
|
|
 |
The SOYBEAN
MEAL INFORMATION CENTER is sponsored by the Soybean Checkoff: Including
the checkoff boards from, Iowa, Kansas, Michigan, Minnesota, Nebraska,
North Dakota, Kentucky and the United Soybean Board |
|
