Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol87.Issue1-2.Sept2000:
Animal Feed Science and Technology
87 (2000) 105±115
Effects of dry matter content on trypsin inhibitors
and urease activity in heat treated soya beans
fed to weaned piglets$
C.E. White*, D.R. Campbell1, L.R. McDowell
Department of Animal Sciences, Institute of Food and Agricultural Sciences, Gainesville, FL 32611, USA
Received 1 April 1999; received in revised form 28 January 2000; accepted 8 June 2000
Abstract
A nutrition study was conducted to evaluate the growth response of weaned piglets fed diets
containing soya beans that had been processed into protein supplements at two different levels of
dry matter (DM) and temperature. Four diets contained protein supplements prepared from whole
full-fat soya beans equilibrated at 800 or 900 g kgÿ1 DM prior to being heated to 110 or 1258C. An
additional diet contained a protein supplement prepared from raw whole full-fat soya beans at
900 g kgÿ1 DM; i.e. an unheated soya bean protein supplement. The experimental control diet was
supplemented with a solvent extracted commercially processed soya bean meal (900 g kgÿ1 DM)
containing 480 g crude protein kgÿ1. Soya beans at 900 g kgÿ1 DM prior to heat treatment at 1108C
produced protein supplements, after heat treatment, that had higher residual levels of trypsin
inhibitors and urease activity than measured in soya beans at 800 g kgÿ1 DM prior to the same heat
treatment. The moisture content of soya beans prior to heat treatment affected the level of heat
necessary to lower values for trypsin inhibitors and urease activity. Soya beans at 800 g kgÿ1 DM
prior to heating at 1108C, produced a protein supplement with similar residual concentrations of
trypsin inhibitors and urease activity to soya beans at 900 g kgÿ1 DM prior to heating at 1258C.
This observation suggested that the soya beans with higher moisture content required lower heat
energy to inactivate trypsin inhibitors and urease. The pen unit response of piglets fed the diet
containing the soya bean protein supplement prepared from soybeans processed at 900 g kgÿ1 DM
and heated to 1108C was not improved when compared to piglets fed the diet containing the
unheated soya bean protein supplement. Soya beans at 800 or 900 g kgÿ1 DM prior to heating to
1108C, or soybeans at 900 g kgÿ1 DM heated to 1258C, produced protein supplements that were
inadequately heat processed as indicated by the values for residual trypsin inhibitors and urease
activity, and, the depressed pen unit response of piglets when compared to those fed the control diet.
$
Florida Agricultural Experiment Station Journal Series no. R-06804.
Corresponding author. Fax: 1-352-392-7652
E-mail address: white@animal.u¯.edu (C.E. White).
1
Present address: Roche Vitamins and Fine Chemicals, Paramus, NJ 07652, USA.
*
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 6 8 - 1
106
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
In contrast, piglets fed the protein supplement prepared from soya beans at 800 g kgÿ1 DM prior to
heating to 1258C, displayed an average daily feed intake and feed-to-gain ratio that did not differ
signi®cantly from piglets fed the control diet. These data indicate that when whole full-fat soya
beans were processed by the dry roasting method, their initial DM content of 800 or 900 g kgÿ1
affected the processing temperature necessary to denature or otherwise inactivate inherent trypsin
inhibitors and urease activity. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Piglets; Soya bean; Trypsin inhibitors; Urease activity
1. Introduction
The soya bean (Glycine max (L.) Merrill) is classi®ed as an oilseed legume and
inadequately heat processed soya beans contain an array of inherent anti-nutritional
factors as reviewed by Liener (1988). Among these are the protease trypsin inhibitors and
urease. When soya beans are subjected to adequate heat processing by any of a number of
commercial or experimental laboratory methods, the trypsin inhibitors and other antinutritional factors are suf®ciently inactivated, and their nutritional components are
improved (Yoshida and Kajimoto, 1988; Marty and Chavez, 1993; Marty et al., 1994;
Marsman et al., 1995; Qin et al., 1996; Zhu et al., 1996; Rajko and Szabo, 1997; DudleyCash, 1999).
Studies by Yoshida and Kajimoto (1988), Marsman et al. (1995), Zhu et al., (1996) and
Rajko and Szabo, (1997), clearly advanced soya bean processing technologies but did not
include animal feeding trials. Marty and Chavez (1993) and Marty et al. (1994) reported
growth response of piglets fed experimental diets where soya beans had been prepared
into protein supplements via a variety of processing methods (extrusion, jetsploding,
roasting or toasting). Further, animal growth response was a criterion used to assess the
quality of single batches of heat processed soybeans, but their experimental design did
not permit identi®cation of the optimal processing temperature necessary to maximize the
animal pen unit response within each processing method evaluated. As a result, the
animal pen unit response within the two studies varied appreciably depending on the
processing method used, suggesting that animal pen unit response was affected by a
combination of factors which included nutritional value, palatability and digestibility,
even when the soya bean protein supplements were considered by the researchers to have
received adequate heat processing.
Qin et al. (1996), showed that experimental variation in feeding steam roasted soya
beans to pigs was introduced by variables such as processing temperature, length of
processing time, the size and variety of the soya bean, and animal pen unit response to the
diet. In the current study we report animal pen unit response of piglets resulting from the
variation in nutritional value of soya bean protein supplements prepared from dry roasting
whole full-fat soya beans processed at 800 or 900 g kgÿ1 DM and 110 or 1258C. The
objective of this study was to compare the pen unit response of piglets fed soya bean
protein supplements prepared by the dry roasting of whole full-fat soya beans at 800 or
900 g kgÿ1 DM prior to dry roasting at 110 or 1258C, using commercially available onfarm equipment.
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
107
2. Materials and methods
2.1. Dietary treatments
The composition of diets is presented in Table 1. The International Feed Number (IFN;
NAS, 1971) is reported in the text herein for each major feed ingredient used as a dietary
energy or protein component. Diets were formulated to contain ground maize (Zea mays)
grain (IFN 4-02-935) as the primary energy source. The soya bean protein supplements
prepared and used in the six dietary treatments were as follows. Diet 1, commercial
solvent extracted soya bean meal (IFN 5-04-612) at 900 g kgÿ1 DM. Diets 2±6 contained
the whole full-fat soya beans (IFN 5-04-610) at either 800 or 900 g kgÿ1 DM. Speci®cally,
diet 2 soya beans were at 900 g kgÿ1 DM when included in the diet as a raw (unheated)
protein supplement; diet 3, soya beans were at 900 g kgÿ1 DM prior to heating to a discharge
temperature of 1108C; diet 4, soya beans were at 800 g kgÿ1 DM prior to heating to a
discharge temperature of 1108C; diet 5, soya beans were at 900 g kgÿ1 DM prior to heating
to a discharge temperature of 1258C; and diet 6, soya beans were at 800 g kgÿ1 DM prior
Table 1
Composition of experimental diets
Ingredients
Control (diet 1)
Soya beans (diets 2±6)
Ground maize
Soya bean meala
Whole full-fat soya beansb
Maize oil
Dicalcium phosphate (CaHPO4)
Limestone
Salt
Trace mineralsc
Vitamin premixd
Antibiotice
684
254
±
30
17
8.0
2.5
1.0
1.0
2.5
1000
569
±
399
±
17
8.0
2.5
1.0
1.0
2.5
1000
Calculated analyses of feed
Crude proteinf (g kgÿ1)
Metabolizable energyg (MJ kgÿ1)
a
180
13.85
180
13.82
Crude protein concentration of commercial soya bean meal, 480 g kgÿ1 as fed basis.
Crude protein concentration of whole full-fat soya beans, 367 g kgÿ1 as fed basis.
c
Calcium Carbonate Company, Quincy, IL. Contained 200 mg zinc, 100 mg iron, 55.0 mg manganese,
11.0 mg copper, 1.5 mg iodine, 1.0 mg cobalt, 20.0 mg calcium and 0.10 mg selenium per kg of feed.
d
Hoffmann LaRoche Company, Nutley, NJ. Supplied 13.2 mg ribo¯avin, 44.0 mg niacin, 26.4 mg
pantothenic acid, 176.0 mg choline chloride, 22.0 ug Vitamin B12, 5500 IU Vitamin A, 880 ICU Vitamin D3
and 22.0 IU Vitamin E per kg of diet.
e
American Cyanamid Company, Princeton, NJ. Supplied 44.0 mg chlortetracycline, 44.0 mg sulfamethazine
and 22.0 mg penicillin per kg of complete diet.
f
Calculated crude protein from nitrogen (N) analysis (N6.25) of individual grain and protein supplement
used as feed in this study, as fed basis.
g
Calculated metabolizable energy based on published estimates (NRC, 1988) for grain and protein
supplements used as feed in this study.
b
108
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
to heating to a discharge temperature of 1258C. The appropriate levels of vitamins and
minerals necessary to meet the growth requirements of piglets 5±20 kg BW (NRC, 1988),
were included in each of the six dietary treatments as shown in Table 1.
2.2. Laboratory preparation of soya bean protein supplements
The ®ve laboratory-prepared protein supplements fed were made from aliquots drawn
from a large uniform batch of whole full-fat soya beans (183 g ether extract kgÿ1, DM
basis) of the `Bragg' variety; i.e. G. max var. Bragg, grown and harvested at a single
location in Alachua County, Florida during a single growing season. The entire quantity
of whole raw full-fat soya beans used to prepare diets 2±6 assayed at 897 g kgÿ1 DM at
ambient conditions of temperature, relative humidity and barometric pressure prior to
processing. This value was rounded up to 900 g kgÿ1 DM for simplicity of reporting. The
DM content of soya beans fed in diets 4 and 6 was decreased prior to dry roasting by
adding 100 g kgÿ1 (w/w) distilled water to an aliquot of soya beans at 900 g kgÿ1 DM.
The soya beans were equilibrated with the water overnight via gentle stirring and
tumbling to ensure uniform moisture absorption. The ®nal DM concentration for soya
beans used in diets 4 and 6 prior to roasting assayed at 795 g kgÿ1 DM and was rounded
up to 800 g kgÿ1 DM, again for simplicity of reporting. To minimize potential
deterioration from prolonged storage of soya beans at 800 g kgÿ1 DM, those used in
diets 4 and 6 were heat processed the morning following overnight equilibration with
water. All aliquots of raw soya beans at either 800 or 900 g kgÿ1 DM were heat processed
by an automated commercial Roast-A-Tron (Mix-Mill, Inc., Bluffton, IN) gas-®red
roaster. Soya beans were roasted at the prescribed temperature control and transit time
settings as recommended in the manufacturer's operations manual to achieve the desired
discharge temperature as speci®ed in diets 3±6. The average transit time through the
roaster was 60 s for soya beans processed to a discharge temperature of 1108C, or 90 s for
soya beans processed to a discharge temperature of 1258C. When heat processing was
completed, the soya beans returned to 90% DM at room temperature, and were ground
into a meal of ®ne particle size before inclusion into their respective diets.
2.3. Commercial soya bean meal
The commercial soya bean meal used in the current study was manufactured by the
solvent extraction process as outlined by Ensminger et al. (1990). Brie¯y, full-fat soya
beans were crushed, then heated to 468C for 15 min. The crushed heated product was then
rolled into ¯akes and passed to an extraction tower where approximately 99% of the soya
oil (190 g soya oil kgÿ1 full-fat soya beans; NRC, 1988) was removed by extraction with
hexane. The de-fatted soya bean meal then passed into a drier and was retained for 10 min
at 988C. Thereafter, the soya bean ¯akes passed into a toaster where they were retained
for 90 min at 1048C, followed by rapid cooling to 388C prior to making a pass through
the grinder. The commercial soya bean meal fed in the current study had an ether extract
residual of 13 g kgÿ1 DM. The fat content of the control diet containing the commercial
soybean meal was adjusted to that of the diets containing full-fat soybeans by adding corn
oil to the ®nal feed formulation presented in Table 1.
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
109
2.4. Analytical determinations
The DM content both before and after heat processing was determined as outlined by
the American Association of Analytical Chemists (AOAC, 1980). Ether extract of the raw
soya beans was also determined according to the AOAC (1980). Representative samples
of the raw soya beans and the commercial soya bean meal were analyzed for crude
protein (nitrogen6.25) content using the procedure for nitrogen determination set forth
by Gallaher et al. (1975) for the Technicon Auto Analyzer (Technicon Industrial Systems,
1978). The residual levels of the trypsin inhibitors expressed as milligrams of protease
inhibitor per gram (mg gÿ1) of de-fatted soya bean sample was measured by the method
of Hamerstrand et al. (1981) both before and after heat processing. Urease activity was
measured as change in pH units (DpH) by the method of Caskey and Knapp (1944).
2.5. Animal feeding trial design
One-hundred and eight Yorkshire±HampshireDuroc crossbred piglets with an average
initial body weight (BW) of 5 kg were allotted by litter origin, BW and sex to receive one
of the six dietary treatments. Each treatment was replicated three times into pen units which
contained six piglets each. The feeding trial was conducted over a period of 35 days. All
piglets were housed in an enclosed climate controlled nursery equipped with elevated pens
having expanded metal ¯oors and wire mesh side panels. Feed and water were offered ad
libitum in each pen unit. The BW of individual piglets, and the feed consumption in each
pen unit, were measured bi-weekly to permit calculations of average daily gain (ADG),
average daily feed intake (ADFI) and the feed-to-gain ratio (F:G) used as animal pen unit
response criteria for statistical analyses that compared effects of dietary treatments.
2.6. Statistical analyses
Variability in ADG of piglets was analyzed by least squares means analysis using the
general linear model of the statistical analysis system (SAS, 1979). The variables ADFI and
F:G were subjected to analysis of variance for a randomized complete block design, where
blocks represented replications within dietary treatments. When calculated values for F were
signi®cant, the Duncan's new multiple range test (Steel and Torrie, 1960) was used to
interpret signi®cant differences among means for ADFI and F:G. Diets 3±6 were further
analyzed as a 22 factorial design evaluating animal pen unit response (ADG, ADFI and
F:G) to the dry matter content of soya beans prior to dry roasting, and the effects of dry
roasting soya beans at the two selected temperatures used to process the protein supplements.
3. Results
3.1. Pen unit response
Table 2 presents the growth response data of piglets assigned the six dietary treatments.
The ADG of piglets fed diet 1, containing the commercial soya bean meal as a protein
110
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
Table 2
Pen unit response of piglets fed diets containing protein supplements from commercial soya bean meal (SBM,
diet 1) or full fat Bragg variety soya beans (diets 2±6) processed at different levels of dry matter and
temperaturea,b
S.E.M.c
Dietary treatment, diet
1
2
Process temperature (8C)
Soya bean dry matter (g kgÿ1)
n/a
900
Ambient 110
900
900
Average
Average
Average
Average
Average
5.04
16.80
0.33 a
0.59 a
1.76 c
5.03
7.87
0.08 d
0.33 b
4.45 ab
initial weight (kg)
®nal weight (kg)
daily gainb (kg)
daily feed intake (kg)
feed-to-gain ratio, F:G
3
5.02
7.56
0.06 d
0.32 b
5.23 a
4
5
6
110
800
125
900
125
800
5.03
9.75
0.13 c
0.41 b
3.09 b
5.03
11.03
0.17 c
0.39 b
2.33 c
5.03
13.71
0.25 b
0.55 a
2.21 c
±
±
0.02
0.02
0.41
a
Means in the same row with different letters are signi®cantly different (P
87 (2000) 105±115
Effects of dry matter content on trypsin inhibitors
and urease activity in heat treated soya beans
fed to weaned piglets$
C.E. White*, D.R. Campbell1, L.R. McDowell
Department of Animal Sciences, Institute of Food and Agricultural Sciences, Gainesville, FL 32611, USA
Received 1 April 1999; received in revised form 28 January 2000; accepted 8 June 2000
Abstract
A nutrition study was conducted to evaluate the growth response of weaned piglets fed diets
containing soya beans that had been processed into protein supplements at two different levels of
dry matter (DM) and temperature. Four diets contained protein supplements prepared from whole
full-fat soya beans equilibrated at 800 or 900 g kgÿ1 DM prior to being heated to 110 or 1258C. An
additional diet contained a protein supplement prepared from raw whole full-fat soya beans at
900 g kgÿ1 DM; i.e. an unheated soya bean protein supplement. The experimental control diet was
supplemented with a solvent extracted commercially processed soya bean meal (900 g kgÿ1 DM)
containing 480 g crude protein kgÿ1. Soya beans at 900 g kgÿ1 DM prior to heat treatment at 1108C
produced protein supplements, after heat treatment, that had higher residual levels of trypsin
inhibitors and urease activity than measured in soya beans at 800 g kgÿ1 DM prior to the same heat
treatment. The moisture content of soya beans prior to heat treatment affected the level of heat
necessary to lower values for trypsin inhibitors and urease activity. Soya beans at 800 g kgÿ1 DM
prior to heating at 1108C, produced a protein supplement with similar residual concentrations of
trypsin inhibitors and urease activity to soya beans at 900 g kgÿ1 DM prior to heating at 1258C.
This observation suggested that the soya beans with higher moisture content required lower heat
energy to inactivate trypsin inhibitors and urease. The pen unit response of piglets fed the diet
containing the soya bean protein supplement prepared from soybeans processed at 900 g kgÿ1 DM
and heated to 1108C was not improved when compared to piglets fed the diet containing the
unheated soya bean protein supplement. Soya beans at 800 or 900 g kgÿ1 DM prior to heating to
1108C, or soybeans at 900 g kgÿ1 DM heated to 1258C, produced protein supplements that were
inadequately heat processed as indicated by the values for residual trypsin inhibitors and urease
activity, and, the depressed pen unit response of piglets when compared to those fed the control diet.
$
Florida Agricultural Experiment Station Journal Series no. R-06804.
Corresponding author. Fax: 1-352-392-7652
E-mail address: white@animal.u¯.edu (C.E. White).
1
Present address: Roche Vitamins and Fine Chemicals, Paramus, NJ 07652, USA.
*
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 6 8 - 1
106
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
In contrast, piglets fed the protein supplement prepared from soya beans at 800 g kgÿ1 DM prior to
heating to 1258C, displayed an average daily feed intake and feed-to-gain ratio that did not differ
signi®cantly from piglets fed the control diet. These data indicate that when whole full-fat soya
beans were processed by the dry roasting method, their initial DM content of 800 or 900 g kgÿ1
affected the processing temperature necessary to denature or otherwise inactivate inherent trypsin
inhibitors and urease activity. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Piglets; Soya bean; Trypsin inhibitors; Urease activity
1. Introduction
The soya bean (Glycine max (L.) Merrill) is classi®ed as an oilseed legume and
inadequately heat processed soya beans contain an array of inherent anti-nutritional
factors as reviewed by Liener (1988). Among these are the protease trypsin inhibitors and
urease. When soya beans are subjected to adequate heat processing by any of a number of
commercial or experimental laboratory methods, the trypsin inhibitors and other antinutritional factors are suf®ciently inactivated, and their nutritional components are
improved (Yoshida and Kajimoto, 1988; Marty and Chavez, 1993; Marty et al., 1994;
Marsman et al., 1995; Qin et al., 1996; Zhu et al., 1996; Rajko and Szabo, 1997; DudleyCash, 1999).
Studies by Yoshida and Kajimoto (1988), Marsman et al. (1995), Zhu et al., (1996) and
Rajko and Szabo, (1997), clearly advanced soya bean processing technologies but did not
include animal feeding trials. Marty and Chavez (1993) and Marty et al. (1994) reported
growth response of piglets fed experimental diets where soya beans had been prepared
into protein supplements via a variety of processing methods (extrusion, jetsploding,
roasting or toasting). Further, animal growth response was a criterion used to assess the
quality of single batches of heat processed soybeans, but their experimental design did
not permit identi®cation of the optimal processing temperature necessary to maximize the
animal pen unit response within each processing method evaluated. As a result, the
animal pen unit response within the two studies varied appreciably depending on the
processing method used, suggesting that animal pen unit response was affected by a
combination of factors which included nutritional value, palatability and digestibility,
even when the soya bean protein supplements were considered by the researchers to have
received adequate heat processing.
Qin et al. (1996), showed that experimental variation in feeding steam roasted soya
beans to pigs was introduced by variables such as processing temperature, length of
processing time, the size and variety of the soya bean, and animal pen unit response to the
diet. In the current study we report animal pen unit response of piglets resulting from the
variation in nutritional value of soya bean protein supplements prepared from dry roasting
whole full-fat soya beans processed at 800 or 900 g kgÿ1 DM and 110 or 1258C. The
objective of this study was to compare the pen unit response of piglets fed soya bean
protein supplements prepared by the dry roasting of whole full-fat soya beans at 800 or
900 g kgÿ1 DM prior to dry roasting at 110 or 1258C, using commercially available onfarm equipment.
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
107
2. Materials and methods
2.1. Dietary treatments
The composition of diets is presented in Table 1. The International Feed Number (IFN;
NAS, 1971) is reported in the text herein for each major feed ingredient used as a dietary
energy or protein component. Diets were formulated to contain ground maize (Zea mays)
grain (IFN 4-02-935) as the primary energy source. The soya bean protein supplements
prepared and used in the six dietary treatments were as follows. Diet 1, commercial
solvent extracted soya bean meal (IFN 5-04-612) at 900 g kgÿ1 DM. Diets 2±6 contained
the whole full-fat soya beans (IFN 5-04-610) at either 800 or 900 g kgÿ1 DM. Speci®cally,
diet 2 soya beans were at 900 g kgÿ1 DM when included in the diet as a raw (unheated)
protein supplement; diet 3, soya beans were at 900 g kgÿ1 DM prior to heating to a discharge
temperature of 1108C; diet 4, soya beans were at 800 g kgÿ1 DM prior to heating to a
discharge temperature of 1108C; diet 5, soya beans were at 900 g kgÿ1 DM prior to heating
to a discharge temperature of 1258C; and diet 6, soya beans were at 800 g kgÿ1 DM prior
Table 1
Composition of experimental diets
Ingredients
Control (diet 1)
Soya beans (diets 2±6)
Ground maize
Soya bean meala
Whole full-fat soya beansb
Maize oil
Dicalcium phosphate (CaHPO4)
Limestone
Salt
Trace mineralsc
Vitamin premixd
Antibiotice
684
254
±
30
17
8.0
2.5
1.0
1.0
2.5
1000
569
±
399
±
17
8.0
2.5
1.0
1.0
2.5
1000
Calculated analyses of feed
Crude proteinf (g kgÿ1)
Metabolizable energyg (MJ kgÿ1)
a
180
13.85
180
13.82
Crude protein concentration of commercial soya bean meal, 480 g kgÿ1 as fed basis.
Crude protein concentration of whole full-fat soya beans, 367 g kgÿ1 as fed basis.
c
Calcium Carbonate Company, Quincy, IL. Contained 200 mg zinc, 100 mg iron, 55.0 mg manganese,
11.0 mg copper, 1.5 mg iodine, 1.0 mg cobalt, 20.0 mg calcium and 0.10 mg selenium per kg of feed.
d
Hoffmann LaRoche Company, Nutley, NJ. Supplied 13.2 mg ribo¯avin, 44.0 mg niacin, 26.4 mg
pantothenic acid, 176.0 mg choline chloride, 22.0 ug Vitamin B12, 5500 IU Vitamin A, 880 ICU Vitamin D3
and 22.0 IU Vitamin E per kg of diet.
e
American Cyanamid Company, Princeton, NJ. Supplied 44.0 mg chlortetracycline, 44.0 mg sulfamethazine
and 22.0 mg penicillin per kg of complete diet.
f
Calculated crude protein from nitrogen (N) analysis (N6.25) of individual grain and protein supplement
used as feed in this study, as fed basis.
g
Calculated metabolizable energy based on published estimates (NRC, 1988) for grain and protein
supplements used as feed in this study.
b
108
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
to heating to a discharge temperature of 1258C. The appropriate levels of vitamins and
minerals necessary to meet the growth requirements of piglets 5±20 kg BW (NRC, 1988),
were included in each of the six dietary treatments as shown in Table 1.
2.2. Laboratory preparation of soya bean protein supplements
The ®ve laboratory-prepared protein supplements fed were made from aliquots drawn
from a large uniform batch of whole full-fat soya beans (183 g ether extract kgÿ1, DM
basis) of the `Bragg' variety; i.e. G. max var. Bragg, grown and harvested at a single
location in Alachua County, Florida during a single growing season. The entire quantity
of whole raw full-fat soya beans used to prepare diets 2±6 assayed at 897 g kgÿ1 DM at
ambient conditions of temperature, relative humidity and barometric pressure prior to
processing. This value was rounded up to 900 g kgÿ1 DM for simplicity of reporting. The
DM content of soya beans fed in diets 4 and 6 was decreased prior to dry roasting by
adding 100 g kgÿ1 (w/w) distilled water to an aliquot of soya beans at 900 g kgÿ1 DM.
The soya beans were equilibrated with the water overnight via gentle stirring and
tumbling to ensure uniform moisture absorption. The ®nal DM concentration for soya
beans used in diets 4 and 6 prior to roasting assayed at 795 g kgÿ1 DM and was rounded
up to 800 g kgÿ1 DM, again for simplicity of reporting. To minimize potential
deterioration from prolonged storage of soya beans at 800 g kgÿ1 DM, those used in
diets 4 and 6 were heat processed the morning following overnight equilibration with
water. All aliquots of raw soya beans at either 800 or 900 g kgÿ1 DM were heat processed
by an automated commercial Roast-A-Tron (Mix-Mill, Inc., Bluffton, IN) gas-®red
roaster. Soya beans were roasted at the prescribed temperature control and transit time
settings as recommended in the manufacturer's operations manual to achieve the desired
discharge temperature as speci®ed in diets 3±6. The average transit time through the
roaster was 60 s for soya beans processed to a discharge temperature of 1108C, or 90 s for
soya beans processed to a discharge temperature of 1258C. When heat processing was
completed, the soya beans returned to 90% DM at room temperature, and were ground
into a meal of ®ne particle size before inclusion into their respective diets.
2.3. Commercial soya bean meal
The commercial soya bean meal used in the current study was manufactured by the
solvent extraction process as outlined by Ensminger et al. (1990). Brie¯y, full-fat soya
beans were crushed, then heated to 468C for 15 min. The crushed heated product was then
rolled into ¯akes and passed to an extraction tower where approximately 99% of the soya
oil (190 g soya oil kgÿ1 full-fat soya beans; NRC, 1988) was removed by extraction with
hexane. The de-fatted soya bean meal then passed into a drier and was retained for 10 min
at 988C. Thereafter, the soya bean ¯akes passed into a toaster where they were retained
for 90 min at 1048C, followed by rapid cooling to 388C prior to making a pass through
the grinder. The commercial soya bean meal fed in the current study had an ether extract
residual of 13 g kgÿ1 DM. The fat content of the control diet containing the commercial
soybean meal was adjusted to that of the diets containing full-fat soybeans by adding corn
oil to the ®nal feed formulation presented in Table 1.
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
109
2.4. Analytical determinations
The DM content both before and after heat processing was determined as outlined by
the American Association of Analytical Chemists (AOAC, 1980). Ether extract of the raw
soya beans was also determined according to the AOAC (1980). Representative samples
of the raw soya beans and the commercial soya bean meal were analyzed for crude
protein (nitrogen6.25) content using the procedure for nitrogen determination set forth
by Gallaher et al. (1975) for the Technicon Auto Analyzer (Technicon Industrial Systems,
1978). The residual levels of the trypsin inhibitors expressed as milligrams of protease
inhibitor per gram (mg gÿ1) of de-fatted soya bean sample was measured by the method
of Hamerstrand et al. (1981) both before and after heat processing. Urease activity was
measured as change in pH units (DpH) by the method of Caskey and Knapp (1944).
2.5. Animal feeding trial design
One-hundred and eight Yorkshire±HampshireDuroc crossbred piglets with an average
initial body weight (BW) of 5 kg were allotted by litter origin, BW and sex to receive one
of the six dietary treatments. Each treatment was replicated three times into pen units which
contained six piglets each. The feeding trial was conducted over a period of 35 days. All
piglets were housed in an enclosed climate controlled nursery equipped with elevated pens
having expanded metal ¯oors and wire mesh side panels. Feed and water were offered ad
libitum in each pen unit. The BW of individual piglets, and the feed consumption in each
pen unit, were measured bi-weekly to permit calculations of average daily gain (ADG),
average daily feed intake (ADFI) and the feed-to-gain ratio (F:G) used as animal pen unit
response criteria for statistical analyses that compared effects of dietary treatments.
2.6. Statistical analyses
Variability in ADG of piglets was analyzed by least squares means analysis using the
general linear model of the statistical analysis system (SAS, 1979). The variables ADFI and
F:G were subjected to analysis of variance for a randomized complete block design, where
blocks represented replications within dietary treatments. When calculated values for F were
signi®cant, the Duncan's new multiple range test (Steel and Torrie, 1960) was used to
interpret signi®cant differences among means for ADFI and F:G. Diets 3±6 were further
analyzed as a 22 factorial design evaluating animal pen unit response (ADG, ADFI and
F:G) to the dry matter content of soya beans prior to dry roasting, and the effects of dry
roasting soya beans at the two selected temperatures used to process the protein supplements.
3. Results
3.1. Pen unit response
Table 2 presents the growth response data of piglets assigned the six dietary treatments.
The ADG of piglets fed diet 1, containing the commercial soya bean meal as a protein
110
C.E. White et al. / Animal Feed Science and Technology 87 (2000) 105±115
Table 2
Pen unit response of piglets fed diets containing protein supplements from commercial soya bean meal (SBM,
diet 1) or full fat Bragg variety soya beans (diets 2±6) processed at different levels of dry matter and
temperaturea,b
S.E.M.c
Dietary treatment, diet
1
2
Process temperature (8C)
Soya bean dry matter (g kgÿ1)
n/a
900
Ambient 110
900
900
Average
Average
Average
Average
Average
5.04
16.80
0.33 a
0.59 a
1.76 c
5.03
7.87
0.08 d
0.33 b
4.45 ab
initial weight (kg)
®nal weight (kg)
daily gainb (kg)
daily feed intake (kg)
feed-to-gain ratio, F:G
3
5.02
7.56
0.06 d
0.32 b
5.23 a
4
5
6
110
800
125
900
125
800
5.03
9.75
0.13 c
0.41 b
3.09 b
5.03
11.03
0.17 c
0.39 b
2.33 c
5.03
13.71
0.25 b
0.55 a
2.21 c
±
±
0.02
0.02
0.41
a
Means in the same row with different letters are signi®cantly different (P