Amino acid digestibility in processed soybean products, rapeseed expellers, and a fermented mixture of co-products fed to weanling pigs

Soybean meal is the most common source of protein in swine diets in the United States. However, conventional soybean meal contains antinutritional factors such as antigenic proteins, oligosaccharides, lectins, and trypsin inhibitors that limit its use in diets fed to weanling pigs. Methods of processing soybean meal to remove antinutritional factors have been developed. These include enzyme treatment, fermentation, and the removal of soluble carbohydrates.

Like soybean meal, rapeseed products are usually not fed to weanling pigs due to the presence of glucosinolates and relatively high concentrations of fiber in these products. Previous research has shown that fermentation of soybean meal can reduce antinutritional factors and fiber concentrations. It is possible that fermentation can make 00-rapeseed meals and 00-rapeseed expellers suitable for feeding to weanling pigs, but no research has been conducted to confirm this hypothesis. An experiment was conducted to determine the standardized ileal digestibility (SID) by weanling pigs of crude protein and amino acids in four sources of processed soybean products, conventional soybean meal, conventional 00-rapeseed expellers, and in a fermented mixture of co-products including 00-rapeseed expellers, wheat bran, potato peel, and soy molasses.

Experimental design

Twenty seven weanling barrows with an average initial body weight of 9.29 kg were surgically equipped with a T-cannula in the distal ileum and fed one of eight diets. The four processed soybean products were two sources of enzyme-treated soybean meal (ESBM-1 and ESBM-2), extruded soybean meal (SBM-EX), and soy protein concentrate (SPC). Another diet contained conventional soybean meal (SBM-CV). Two rapeseed products were also tested: conventional 00-rapeseed expellers (RSE), and a fermented co-product mixture (FCM) containing 00-rapeseed meal, wheat, soy molasses, and potato peel. Seven of the diets each contained one of the seven test ingredients as the sole source of amino acids. In addition, a nitrogen-free diet was used to calculate basal endogenous losses of crude protein and amino acids. Ileal digesta were collected and analyzed to determine amino acid digestibility.

Results

The concentration of crude protein ranged from 47.81% to 62.05% in the soybean meal products and from 30.13% to 32.00% in the rapeseed products (Table 1).

Among soy products, the SID of crude protein was the same in ESBM-1, ESBM-2, SBM-EX, and conventional soybean meal (Table 2). The SID of crude protein in SPC was less than that in ESBM-1.The SID for the mean of all indispensable amino acids did not differ among soy products.

The SID of lysine and the lysine:crude protein ratio in ESBM-2 was less than that in SBM-CV, indicating that this product may have been damaged by excessive heat during processing.

The SID of crude protein and most amino acids was greater in the processed soy products than in the rapeseed products. For crude protein and all amino acids, SID values in RSE were greater than in FCM.

Key points

  • Digestibility of crude protein and most amino acids was the same in the four processed soy products as in SBM-CV. However, reduced lysine digestibility and lysine:crude protein ratio in ESBM-2 indicated possible heat damage.
  • Crude protein and amino acid digestibility in SPC was less than in ESBM-1, indicating that this particular source of SPC was not of as high quality as other processed soybean products.
  • The digestibility of crude protein and amino acids in rapeseed products was generally less than in soy products.
  • Fermentation did not improve amino acid digestibility in rapeseed expellers; FCM had the least digestible amino acids of all of the ingredients tested. This may be due to damage in the drying process, or to inclusion of low-quality ingredients in FCM.

 

Table 1. Analyzed crude protein and amino acid composition of enzyme-treated soybean meal (ESBM-1 and ESBM-2), extruded soybean meal (SBM-EX), soy protein concentrate (SPC), conventional soybean meal (SBM-CV), conventional 00-rapeseed expellers (RSE), and a fermented 00-rapeseed coproduct mixture (FCM) fed to pigs

 

Ingredient

Item

ESBM-1

ESBM-2

SBM-EX

SPC

SBM-CV

RSE

FCM

CP, %

56.82

52.07

53.28

62.05

47.81

30.13

32.00

Indispensable AA, %

             

   Arg

4.00

3.64

3.75

4.54

3.44

1.73

1.80

   His

1.43

1.31

1.30

1.57

1.22

0.79

0.75

   Ile

2.63

2.38

2.40

2.93

2.18

1.21

1.11

   Leu

4.31

3.89

4.02

4.85

3.60

1.96

2.12

   Lys

3.64

3.14

3.17

3.90

3.02

1.78

1.65

   Met

0.74

0.70

0.67

0.82

0.65

0.59

0.59

   Phe

2.86

2.57

2.71

3.22

2.37

1.16

1.27

   Thr

2.10

1.92

1.95

2.35

1.79

1.28

1.31

   Trp

0.74

0.65

0.70

0.77

0.66

0.39

0.37

   Val

2.82

2.57

2.49

3.08

2.35

1.47

1.58

Total Indispensable AA, %

25.27

22.77

23.16

28.03

21.28

12.36

12.55

Dispensable AA, %

             

   Ala

2.43

2.22

2.20

2.66

2.03

1.26

1.43

   Asp

6.28

5.72

5.94

7.08

5.35

2.10

2.27

   Cys

0.74

0.70

0.65

0.77

0.62

0.65

0.68

   Glu

9.54

8.65

8.96

10.69

8.17

4.47

4.93

   Gly

2.33

2.13

2.12

2.54

1.96

1.43

1.52

   Pro

2.92

2.63

2.63

3.13

2.33

1.74

1.98

   Ser

2.45

2.22

2.40

2.81

2.10

1.17

1.19

   Tyr

1.99

1.81

1.88

2.19

1.68

0.85

0.93

Total AA, %

53.95

48.85

49.94

59.90

45.52

26.03

27.48

 

 

Table 2. Standardized ileal digestibility (SID) of crude protein and amino acids in enzyme-treated soybean meal (ESBM-1 and ESBM-2), extruded soybean meal (SBM-EX), soy protein concentrate (SPC), conventional soybean meal (SBM-CV), conventional 00-rapeseed expellers (RSE), and a fermented 00-rapeseed coproduct mixture (FCM) fed to pigs

 

Ingredient

P-value

Item

ESBM-1

ESBM-2

SBM-EX

SPC

SBM-CV

RSE

FCM

 

CP, %

89.92a

85.20abc

86.19ab

82.19bc

87.99ab

79.50c

70.60d

<0.01

Indispensable AA, %

               

  Arg

96.88a

93.48abc

95.03ab

92.26bc

95.44ab

90.12c

81.06d

<0.01

  His

93.41a

90.64ab

90.27ab

88.88b

91.51ab

87.93b

79.56c

<0.01

  Ile

91.71a

88.90ab

89.90ab

87.34b

89.71ab

81.29c

74.35d

<0.01

  Leu

91.65a

89.22ab

89.64ab

87.50bc

89.65ab

84.94c

78.36d

<0.01

  Lys

87.34ab

82.51bc

86.39ab

86.52ab

89.15a

80.19c

64.17d

<0.01

  Met

92.92a

90.47abc

90.63abc

88.82bc

92.06ab

87.77c

83.71d

<0.01

  Phe

92.60a

90.07ab

90.80ab

88.78b

89.91ab

85.29c

79.93d

<0.01

  Thr

87.51a

83.93a

85.28a

85.97a

87.25a

78.05b

70.55c

<0.01

  Trp

93.33a

89.95ab

91.09ab

89.99ab

92.30ab

89.00b

85.29c

<0.01

  Val

89.95a

86.18a

86.42a

86.40a

88.22a

78.85b

71.36c

<0.01

  Mean

91.42a

88.25a

89.93a

88.28a

90.32a

83.84b

75.23c

<0.01

Dispensable AA, %

               

  Ala

88.25a

83.92ab

85.40ab

81.30b

86.95ab

81.53b

73.22c

<0.01

  Asp

88.53a

86.32a

85.28a

85.81a

87.77a

81.10b

69.72c

<0.01

  Cys

82.26ab

77.30b

79.33ab

79.03ab

84.64a

80.54ab

70.20c

<0.01

  Glu

90.05a

87.12a

87.89a

88.06a

90.15a

87.49a

81.78b

<0.01

  Gly

86.59a

77.67a

81.07a

74.47ab

86.22a

80.22a

61.92b

<0.01

  Pro

101.18a

80.32ab

91.56a

55.39b

97.21a

83.05ab

22.47c

<0.01

  Ser

91.97a

89.16a

91.25a

90.41a

91.82a

81.41b

74.83c

<0.01

  Tyr

92.43a

89.52a

90.85a

90.39a

90.61a

81.15b

76.67c

<0.01

  Mean

90.04a

83.82ab

85.59ab

81.31b

88.91ab

83.69ab

67.41c

<0.01

Total AA, %

90.64a

86.11abc

87.34abc

84.05bc

89.60ab

83.56c

71.10d

<0.01

a-eMeans within a row lacking a common superscript letter differ (P < 0.05).

This report is based on unpublished research by D. M. D. L. Navarro, Y. Liu, T. B. Christensen, and H. H. Stein.

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