Digestibility of amino acids in corn, corn co-products, and bakery meal fed to growing pigs

Rising costs of traditional swine feeds are causing many producers to look for alternative feedstuffs to deliver nutritional value at a lower cost. The corn milling and fermentation industries, and the human food industry, create co-products which can be fed to livestock.  One of these, distillers dried grains with solubles (DDGS), has been found to be suitable for inclusion in swine diets up to 30%. Other co-products have not been as extensively studied. This experiment was performed to measure the apparent (AID) and standardized (SID) ileal digestibility of crude protein and amino acids in corn gluten meal, corn gluten feed, corn germ meal, hominy feed, and bakery meal in growing pigs and to compare these values to the values observed for DDGS and corn.

Alternative feedstuffs

Hominy feed is a co-product from the dry milling industry, and consists of the hull and starchy endosperm of corn kernels. Corn gluten meal, corn gluten feed, and corn germ meal are co-products from the wet milling process, in which corn is steeped in water before being separated into its components. Corn germ meal consists of the germ after extraction of the oil. Corn gluten meal consists mainly of the gluten portion of the kernel, after the germ and bran have been removed and the starch has been mechanically separated out. Corn gluten feed consists of the bran combined with condensed solubles from the steepwater. Bakery meal is produced from waste wheat products, pasta, snack foods, baked goods, and breakfast cereals. 

AA digestibility

Eight diets were prepared. Seven of the diets contained commercial yellow dent corn, DDGS, hominy feed, corn gluten meal, corn gluten feed, corn germ meal, or bakery meal as the sole source of protein and amino acids. The eighth diet contained no protein and was used to measure the basal endogenous loss of protein and amino acids. Ileal digesta were collected and analyzed for protein content, and SID was calculated by subtracting endogenous loss from the total ileal protein/amino acid output.

Corn gluten meal had the greatest (P < 0.01) AID for crude protein and all indispensable amino acids of all ingredients used in this experiment, including corn and DDGS. The mean AID for indispensable amino acids in corn gluten feed, corn germ meal, hominy feed, and bakery meal did not differ from corn or DDGS.

The SID of crude protein was greater (P < 0.01) in corn and corn gluten meal than in all other ingredients (Table 2). The SID of crude protein in DDGS, bakery meal, corn germ meal, corn gluten feed, and hominy meal did not differ from each other.

The SID of lysine in corn gluten meal and corn gluten feed was greater (P < 0.01) than in DDGS, bakery meal, corn germ meal, and hominy feed, and was the same as that of corn.  For all indispensable amino acids except argininine, the SID values in corn gluten meal did not differ from those of corn. SID of indispensable amino acids in bakery meal, corn gluten meal, corn gluten feed, corn germ meal, and hominy feed was in most cases less than that in corn, but the same or greater than that in DDGS.

Key points

  • While values for digestibility of crude protein and amino acids in corn DDGS are known, digestibility values for other corn co-products have yet to be determined.
  • For most amino acids, SID in bakery meal, corn gluten meal, corn gluten feed, corn germ meal, and hominy feed is comparable to or greater than that of DDGS.
  • With the exception of arginine, crude protein and amino acid SID of corn gluten meal is comparable to corn.



 Table 1. Apparent ileal digestibility (AID) of AA in corn, corn co-products, and bakery meal fed to growing pigs.

 

Dietary treatments

 

Item

Corn

DDGS

BM

CGluM

CGF

CGerM

HF

SEM

P-value

CP, %

59.0b

53.8bc

54.1bc

77.5a

52.1bc

55.2b

47.5c

2.36

< 0.01

Indispensable AA, %

  Arg

74.1c

65.5d

72.3c

83.9a

71.7c

81.1ab

75.8bc

1.77

< 0.01

  His

74.9ab

70.3bc

66.1c

79.6a

70.2bc

73.5b

72.1bc

1.97

< 0.01

  Ile

72.1b

69.7bc

65.4cd

84.2a

70.7bc

72.6b

62.2d

2.14

< 0.01

  Leu

83.3b

82.1b

74.8c

90.4a

78.2bc

76.6c

79.3bc

1.65

< 0.01

  Lys

58.0bc

39.2d

39.7d

73.6a

64.0ab

64.4ab

50.6cd

3.61

< 0.01

  Met

82.3b

79.3bc

73.5d

89.9a

75.3cd

78.6bc

73.1d

1.68

< 0.01

  Phe

79.6b

77.2bc

73.4c

88.0a

75.9bc

78.8b

73.0c

1.78

< 0.01

  Thr

57.8cde

60.6bcd

50.6e

78.6a

68.4b

63.8bc

51.0de

2.87

< 0.01

  Trp

64.9c

75.6b

75.9b

86.8a

80.0b

76.5b

66.2c

1.91

< 0.01

  Val

70.3bc

68.4bcd

63.3d

81.9a

68.7bcd

72.0b

62.8cd

2.2

< 0.01

Mean

74.5b

70.8b

71.3b

86.0a

72.0b

74.1b

68.7b

2.27

< 0.01

Dispensable AA, %

  Ala

72.9b

70.1b

63.0c

84.9a

69.5b

68.7bc

67.4bc

2.25

< 0.01

  Asp

62.7b

60.7b

52.8c

79.2a

58.0bc

60.8b

57.6bc

2.57

< 0.01

  Cys

69.8b

67.6bc

62.3cd

78.0a

58.3d

57.4d

67.6bc

2.27

< 0.01

  Glu

81.2ab

77.6bc

78.2bc

86.1a

72.1d

73.8cd

76.9bcd

1.64

< 0.01

  Gly

30.9

24.6

41

39.2

36.4

42.9

35.3

5.78

0.27

  Pro

6.4ab

-20.6bc

45.8a

53.2a

7.3ab

-44.5c

6.6abc

17

< 0.01

  Ser

70.6b

68.5b

65.5b

86.0a

66.6b

67.7b

69.9b

2.05

< 0.01

  Tyr

77.6b

76.5bc

71.8c

88.0a

74.9bc

75.2bc

70.7c

1.83

< 0.01

Mean

61.7bc

53.6c

68.1b

77.5a

55.5c

53.9c

58.5bc

3.68

< 0.01

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

 

Table 2. Standardized ileal digestibility (SID) of AA in corn, corn co-products, and bakery meal fed to growing pigs.

 

Dietary treatments

 

Item

Corn

DDGS

BM

CGluM

CGF

CGerM

HF

SEM

P-value

CP, %

89.1a

70.5b

72.5b

85.5a

70.9b

69.5b

74.8b

2.51

< 0.01

Indispensable AA, %

  Arg

100.1a

81.3d

91.5bc

93.7bc

90.4c

89.7c

96.3ab

1.77

< 0.01

  His

83.7a

75.5cd

72.5d

82.8ab

75.9cd

77.6bcd

79.8abc

1.97

< 0.01

  Ile

80.9ab

74.7bc

71.0c

86.4a

76.6bc

76.7bc

70.8c

2.14

< 0.01

  Leu

88.0ab

84.8bc

78.2e

91.3a

82.2cde

79.8de

83.8bcd

1.66

< 0.01

  Lys

69.2ab

46.0d

48.4cd

78.7a

68.8ab

68.4b

58.8bc

3.61

< 0.01

  Met

86.2ab

81.6bc

76.5d

90.6a

78.8cd

80.8cd

77.0cd

1.68

< 0.01

  Phe

85.9ab

81.1bc

77.7c

89.4a

81.2bc

82.0bc

79.2c

1.78

< 0.01

  Thr

74.9ab

69.5bc

62.1c

83.5a

75.2ab

71.3b

65.8bc

2.87

< 0.01

  Trp

83.9bc

82.6bc

83.1bc

91.8a

87.5ab

81.4c

82.4bc

1.91

< 0.01

  Val

80.1ab

73.9bc

69.8c

84.9a

74.9bc

76.0bc

71.7c

2.2

< 0.01

Mean

84.9ab

76.7c

78.5bc

88.6a

78.7bc

78.9bc

78.0bc

2.27

< 0.01

Dispensable AA, %

  Ala

86.6ab

77.8c

73.0c

87.8a

77.9c

75.8c

79.3bc

2.25

< 0.01

  Asp

77.2ab

68.1c

62.2c

83.2a

66.4c

66.4c

68.8bc

2.57

< 0.01

  Cys

79.6ab

73.4bc

69.0cd

81.0a

65.2d

64.1d

76.1abc

2.27

< 0.01

  Glu

87.7a

81.8bc

81.8bc

87.6a

77.1c

77.8bc

82.9ab

1.64

< 0.01

  Gly

107.4a

64.8d

88.7bc

66.5d

76.2cd

68.6d

97.1ab

5.78

< 0.01

  Pro

193.3a

86.4c

158.2ab

97.2c

130.9bc

98.9c

190.2a

14.51

< 0.01

  Ser

85.1ab

76.9cd

75.6d

89.7a

77.1cd

75.1d

82.4bc

2.05

< 0.01

  Tyr

84.8ab

81.1bc

77.0c

89.6a

81.0bc

79.4bc

77.8c

1.83

< 0.01

Mean

103.3a

77.8d

94.1ab

83.6bc

83.5cd

76.2d

95.6ab

3.7

< 0.01

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

 

This research report is based on unpublished research by F. N. Almeida and H. H. Stein.

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