Department of Animal Science Florida Agricultural
Research Report AL-1984-6 -29- Experiment Station
May, 1984 Gainesville, FL
Performance of Growing-Finishing Swine Fed Diets Containing
Soybean Meal or Soybeans with Varying Heat TreatmentsI
D. R. Campbell, M. T. Coffey and G. E. Combs2
During periods of low demand for soybean oil or low price for whole
soybeans, it is economical to include whole "full-fat" soybeans in swine
diets. Since whole soybeans contain not only high quality protein (38-42%)
but are also a rich source of energy due to the oil which they contain
(18-22%), they have the potential of supplying major quantities of both
energy and protein for all types of swine feeds. However, the major drawback
of including whole soybeans in swine feeds is that they contain
anti-nutritonal factors which require heat processing to destroy. The most
important anti-nutritional factor in soybeans Is trypsin inhibitor. Soybeans
also contain urease which has little nutritional importance In swine diets
except that the urease content Is used to evaluate optimum heat processing.
Heating the soybeans reduce both the trypsin inhibitor and urease contents.
Soybean meal processing plants monitor the urease content while producing
soybean meal and considers soybeans having a urease index less than .20 to be
adequately processed. Two on-the-farm methods of heat processing whole
soybeans (roasters and extruders) currently available for swine producers
have increased the feasibility of including whole soybeans in swine diets.
The objectives of these studies were to compare performance of
growing-finishing pigs fed diets containing "weathered" soybeans (heated and
unheated) to a corn-soybean meal diet. The Bragg variety of soybeans were
defined as "weathered" due to remaining In the field a period of time
considered longer than normal before being harvested.
Two trials were conducted utilizing 117 crossbred pigs. Six pigs were
assigned to each pen on the basis of initial weight, sex and litter origin.
Both trials consisted of three replicate pens per treatment. The heated
whole soybeans were passed through a Roast-A-Tron3 gas-fired roaster.
Afterwards, the heated and unheated soybeans were ground in a hammer mill
before inclusion into their respective diets. The diet compositions are
presented in Table 1.
Trial 1. Forty-five pigs averaging 37.9 kg were randomly assigned to the
following three treatments: (1) a corn-soybean.meal diet; (2) a
2Campbell, Graduate Research Assistant; Coffey, Assistant Animal
Nutritionist; and Combs, Animal Nutritionist, Department of Animal
3Mix-Mill, Inc., Bluffton, IN.
corn-unheated soybean diet or (3) a corn-heated soybean (110 C) diet. The
grower diet was fed for 28 days then all pens were changed to their
respective finishing diet. After a 56-day finisher period, the diets were
switched on the pigs consuming the whole soybean diets and pig performance
was observed an additional 14 days. The pigs consuming the unheated soybean
diet received the heated soybean diet and the pigs fed the heated soybean
diet received the unheated soybean diet.
Trial 2. Seventy-two pigs averaging 71 kg were fed the finisher diets
presented in table 1. The dietary treatments were (1) soybean meal; (2)
unheated soybeans; (3) soybeans heated to 110 C and (4) soybeans heated to
All pigs in both studies were housed in a semi-enclosed concrete
growing-finishing barn with solid floors. Feed and water were supplied ad
libitum. Pig weights and feed consumption were determined bi-weekly. The
growth data were analyzed by least squares analysis of variance with initial
weight as a covariate. Feed intake and feed efficiency data were subjected
to analysis of variance for a randomized complete block design. Duncan's
multiple range test was used to determine treatment differences.
Results and Discussion
The results from trial 1 are presented in table 2. In the grower period,
feed intake, feed to gain ratio, and growth of pigs fed unheated soybeans
were adversely affected (P<.05) compared to the pigs fed soybean meal or
heated soybean diets. Pig growth, feed efficiency and feed intake between
the soybean meal and heated soybean diets did not differ (P>.05).
During the finisher period, raw soybeans continued to be an inadequate
protein supplement for pigs. Heating the soybeans to 110 C significantly
(P<.05) Improved feed Intake, pig growth and feed to gain ratio However,
feed consumption and pig growth were still depressed (P<.05) when compared to
the pigs fed the soybean meal diet. Feed efficiency did not differ between
the heated soybean and soybean meal diets.
Average daily weight gain, feed efficiency and feed intake were reduced
(P<.05) by feeding raw soybeans during the entire trial. The depressed
(P<.05) feed intake and growth of pigs fed heated soybeans during the
finishing period resulted in an overall reduction (P<.05) in these dependent
variables. However, pigs utilized the heated soybeans equally efficient
(P>.05) when compared to soybean meal.
These data are in contrast of previous work (Fla. Res. Rept. AN-1970-2)
which reported raw and heated soybeans were adequate protein supplements for
finishing pigs. The previous study also indicated that the quality of heat
processing of soybeans was less critical as the pig matures. The heated
soybeans were an inadequate feed ingredient for three week-old pigs.
However, the heated soybeans were adequate for nine and sixteen week-old
pigs. Likewise, performance of the three and nine week-old pigs was
adversely affected by feeding raw soybeans but the sixteen week-old pigs
could adequately utilize the raw soybeans. These results are in contrast
with data from this study. A reason why the heated soybeans were adequate
during the grower and not the finisher period is not readily apparent.
At the end of the study, when the pigs fed the heated soybean diet were
offered the raw soybean diet, pig growth was promptly reduced (P<.01) and
feed to gain ratio was increased (P<.06) (table 3). Feed intake declined but
did not significantly differ (P>.05). Conversely, when pigs fed the raw
soybean diet received the heated soybean diet, pig growth quickly increased
(P<.01) and feed to gain ratio decreased (P=.03). Feed intake was improved
but did not significantly differ (P>.05).
A summary of the performance data of trial 2 are presented in table 4.
Daily gain and feed efficiency of pigs fed raw soybeans were significantly
reduced (P<.05) when compared to pigs fed the soybean meal diet. Heating raw
soybeans to 110 C did not Improve (P>.05) their feeding vilue. To obtain
similar growth of pigs fed the soybean meal diet, it was necessary to roast
the raw soybeans to 125 C. Roasting the raw soybeans at 110 C did not
provide equal growth to pigs fed the soybean meal diet. Feed efficiency of
pigs fed soybean meal and soybeans heated at 110 C or 125 C did not differ
(P>.05). Feed intake was not influenced by the experimental factors.
Previous research data have been inconsistent regarding the feeding value
of raw and roasted soybeans for growing-finishing pigs. The present data
provide additional evidence of this inconsistency. Feeding raw soybeans
depressed feed intake in trial 1 and not in trial 2. Heating raw soybeans to
110 C improved their feeding value in trial 1 but not in trial 2. The causes
for these discrepancies are not evident. However, the pigs in Trial 2 were
heavier and more mature than the pigs involved in Trial 1. The feed intake
of the older pigs appears to be influenced less by the quality of soybean
protein being consumed. The depressed performance of finishing pigs fed raw
soybeans contradict previous results (Fla. Res. Rept. AN-1970-2) but could be
due to the fact that the soybeans in this study remained in the field an
extended period of time before being harvested.
The Bragg soybeans in these studies contained 98.0 units of trypsin
inhibitor (TI) per mg sample which is higher than normally found in soybeans
(50-80 Tl/mg). The urease index of the unheated soybeans and soybeans heated
to 110 and 125 C were 1.95, 1.86 and .86, respectively. The inferior
performance of pigs fed the raw soybeans and lack of Improvement resulting
from roasting soybeans at 110 C typifies their high urease indexes. The data
indicates that soybeans having a urease index of .86 are adequate protein
supplements for pigs initially weighing 71 kg although this urease index
(.86) Is considered by soybean meal processing plants as being inadequately
Two trials utilizing 117 crossbred pigs to compare the performance of
growing-finishing pigs fed diets containing soybean meal and raw and heated
soybeans.. Performance of pigs fed the raw soybean diet was significantly
reduced (P<.05) with pigs weighing either 38 or 71 kg initially when compared
to pigs fed the soybean meal diet. Heating raw soybeans to 110 C permitted
equal performance to growing pigs fed soybean meal. However, finishing pigs
fed soybeans roasted at 110 C did not grow at a similar rate as pigs fed the
soybean meal diet. Roasting soybeans at 125 C decreased their urease index
to .86 and permitted equal average daily gain and feed efficiency of 71 kg
pigs fed a soybean meal diet. The unheated soybeans were inadequate protein
supplements for both growing and finishing pigs. Additional research is
needed to explain differences noted between these two trials.
TABLE 1. PERCENTAGE COMPOSITION OF EXPERIMENTAL DIETS
Grower Diets Finisher Diets
Ingredients Control Soybeans Control Soybeans
Ground yellow corn 76.80 70.30 82.65 77.35
Soybean meal 20.00 --- 14.40 ---
Whole soybeans ---- 26.50 ---- 19.70
Dynafos 1.70 1.70 1.70 1.70
Limestone 0.80 0.80 0.80 0.80
lodized Salt 0.25 0.25 0.25 0.25
Trace Minerals (CCC)1 0.10 0.10 0.10 0.10
Vitamin premix (UF)2 0.10 0.10 0.10 0.10
ASP-250 0.25 0.25 --- ---
1Provided by Calcium Carbonate Company, Quincy, IL contained 20% zinc, 10%
iron, 5.5% manganese, 1.1% copper, 0.15% iodine, 0.10% cobalt and 2% calcium.
2Supplied 13,200 mg riboflavin; 44,000 mg niacin; 26,400 mg pantothenic acid,
176,000 mg choline chloride; 22,000 mcg vitamin B12; 5,500,000 IU vitamin A;
880,00 ICU Vitamin D3 and 22,000 IU vitamin E per kg of premix.
TABLE 2. PERFORMANCE OF GROWING-FINISHING PIGS FED DIETS CONTAINING SOYBEAN
MEAL OR SOYBEANS (UNHEATED OR HEATED), TRIAL 1a
Control Unheated Heated
Average initial weight, kg 37.86 37.86 37.86
Daily cain, kg .78b .43 .76b
Daily feed intake, kg 2.31b 1.82c 2.24b
Feed/gain 2.95b 4.31c 2.94b
Average initial weight, kg 59.77 50.00 59.14
Daily gain, kg .78b .42d .69c
Daily feed intake, kg 2.82b 1.90d 2.55c
Feed/gain 3.62b 4.50c 3.72b
Average initial weight, kg 37.86 37.86 37.86
Average final weight, kg 103.36 73.64 97.50
Daily gain, kg .78b .43d .71c
Daily feed intake, kg 2.65b 1.87d 2.44c
Feed/gain 3.40b 4.42c 3.44b
aLeast squares means for daily gain and treatment means for feed values.
b,c,dMeans in same row with different superscripts are different (P<.05).
TABLE 3. PERFORMANCE OF PIGS BEFORE AND AFTER CHANGING THE SOYBEAN DIETS,
Period (14 days)
Initial raw soybean diet changed to heated soybean diet
Daily gain, kg .47a .83b
Daily feed intake, kg 2.29 2.69
Feed/gain 4.67c 3.27d
Initial heated soybean diet changed to raw soybean diet
Daily gain, kg .60a .41b
Daily feed intake, kg 2.56 2.22
Feed/gain 4.26c 5.36d
a,bMeans in same row with different superscripts are different (P<.01).
c,dMeans in same row with different superscripts are different (P<.06).
TABLE 4. PERFORMANCE OF FINISHING PIGS FED DIETS CONTAINING SOYBEAN MEAL OR
SOYBEANS WITH VARYING HEAT TREATMENTS, TRIAL 2a
Control Unheated 110 C 125 C
Average initial weight, kg 71.00 71.00 71.00 71.00
Average final weight, kg 105.36 100.27 99.64 103.59
Daily gain, kg .70b .60c .59c .66b
Feed/gain 3.92b 4.63C 4.28bc 3.91b
Daily feed intake, kg 2.73 2.77 2.50 2.59
aLeast squares means for daily gain and treatment means for feed values.
b,cMeans in same row with different superscripts are different (P<.05).