Amino acid digestibility in four sources of canola meal and soybean meal fed to growing pigs

Due to the increasing demand for protein for livestock feeding, the interest in using canola meal in diets fed to swine is increasing. Canola meal is a product of the rapeseed plant, an abundant oilseed crop grown in Canada, the Northern United States, and parts of Europe. The oil is extracted for use in cooking and agriculture, leaving a high-protein meal that can be used in livestock feeding. Although the concentration of protein and amino acids and the amino acid profile of canola meal is less desirable than that of soybean meal, its relatively low cost may make it an attractive option for producers. Recently, new varieties of canola that contain more protein and less fiber have been selected. The de-oiled meals of these varieties have a concentration of crude protein that is close to that of de-hulled soybean meal.  However, there is no information about the digestibility of amino acid in high protein canola meal when fed to pigs.

It has also been speculated that changes in the traditional pre-press solvent extraction oil removal procedure may improve the quality of canola meal. The traditional procedure involves use of heat to desolventise the de-oiled meal, but a new procedure allows for production of canola meal using a low-temperature procedure. There are, however, no comparative data between meals produced using the traditional high temperature procedure and meals produced using the low-temperature procedure.

Therefore, an experiment was conducted with the objective of comparing the digestibility of amino acids in high-protein canola meal with the digestibility of amino acids in conventional canola meal and in soybean meal. The second objective was to compare the digestibility of amino acids in canola meal produced using a low-temperature process with that of canola meal produced using a traditional high-temperature process.
 

Experimental design

Four sources of canola meal and one source of soybean meal were used (Table 1). One source of canola meal was produced from a new high-protein variety of canola (CM-HP) and contained 44.7% crude protein. Two additional sources of canola meal were produced from a conventional source of canola, but one source was produced using a traditional prepress-solvent extraction procedure using heating to desolventise the meal (CM-HT) whereas the other source was produced using a low-temperature crushing procedure (CM-LT). The last source of canola meal was a conventional source of canola meal (CM-CV). The soybean meal that was used was also a conventional source of de-hulled soybean meal.

Twelve growing barrows with an average initial body weight of 34.0 kg were allotted to a repeated 6 x 6 Latin square design. Six experimental diets were prepared: one diet was based on soybean meal and four diets were based on each of the four sources of canola meal. In each of these diets, soybean meal or canola meal was the sole source of protein in the diet. In addition to these five diets, an N-free diet that was used to estimate the basal endogenous losses of crude protein and amino acids from the pigs was also formulated.

Ileal digesta were collected and analyzed to determine the apparent ileal digestibility of crude protein and amino acids in each protein source. AID values were adjusted for basal endogenous losses of protein and amino acids to calculate standardized ileal digestibility.

 

Results

The digestibility values for crude protein and all amino acids were greater (P < 0.05) in soybean meal than in any of the four sources of canola meal, but the digestibility of crude protein and most amino acids did not differ among the four samples of canola meal (Table 2).  Conventional canola meal had less (P < 0.05) digestibility of isoleucine than the other canola meal samples, while the low-temperature processed canola meal had less (P < 0.05) digestibility of tryptophan than the other canola meals. The high protein canola meal had a greater (P < 0.05) digestibility of lysine than the other canola meals, and the digestibility of lysine in both the high temperature processed and the low temperature processed canola meals  was greater (P < 0.05) than in conventional canola meal. Cysteine digestibility was greater  (P < 0.05) in the high temperature processed canola meal than in the high protein canola meal and the conventional canola meal.

 

Selecting for high protein does not decrease amino acid digestibility

The digestibility of crude protein and all amino acids in the high protein canola meal was equal to or greater than in the conventional canola meal indicating that the selection for the high protein concentration did not negatively influence digestibility of amino acids. The feeding value of the high protein canola meal is, therefore, greater than in conventional canola meal because the increased concentration of crude protein and amino acids results in increased concentrations of digestible amino acids, which the pigs can utilize for protein synthesis. However, although the concentration of crude protein in the high-protein canola meal is close to that of de-hulled soybean meal, the concentration and the digestibility of amino acids in high-protein canola meal is less than in de-hulled soybean meal.

 

Processing temperature does not affect amino acid digestibility

The fact that no differences were observed between the high-temperature canola meal and the low-temperature canola meal indicates that there is no advantage of using the low-temperature production process. This observation also indicates that the temperature used in the desolventiser process of the traditional pre-press de-oiling procedure is not detrimental to amino acid digestibility.

 

Key points

  • The digestibility of crude protein and amino acids was less in canola meal than in soybean meal regardless of the source of soybean meal used.
  • Amino acids in high-protein canola meals are as digestible or better digestible than the amino acids in conventional canola meal.
  • More digestible amino acids will be provided to pigs if high-protein canola meal is used rather than conventional canola  meal.
  • Processing canola meal at lower temperatures does not improve amino acid digestibility.

 

Table 1. Concentration of crude protein and amino acids in soybean meal (SBM), high protein canola meal (CM-HP), conventional canola meal (CM-CV), and canola meal processed at high or low temperatures (CM-HT and CM-LT, respectively)

 

Ingredient

Item

SBM

CM-HP

CM-HT

CM-LT

CM-CV

  CP, %

47.11

44.72

36.02

36.99

34.2

Indispensable AA, %

       

  Arg

3.25

2.5

2.05

2.13

1.87

  His

1.16

1.14

0.94

0.98

0.86

  Ile

2.16

1.71

1.48

1.53

1.34

  Leu

3.49

2.93

2.46

2.54

2.29

  Lys

2.85

2.41

2.01

2.1

1.8

  Met

0.64

0.83

0.69

0.72

0.67

  Phe

2.27

1.65

1.38

1.44

1.3

  Thr

1.71

1.69

1.42

1.47

1.43

  Trp

0.69

0.61

0.45

0.47

0.4

  Val

2.24

2.19

1.85

1.92

1.72

Dispensable AA, %

       

  Ala

1.95

1.82

1.53

1.58

1.44

  Asp

5.07

3.09

2.41

2.49

2.42

  Cys

0.59

1.05

0.79

0.84

0.74

  Glu

7.98

7.07

5.7

5.86

5.25

  Gly

1.9

2.03

1.74

1.81

1.67

  Pro

2.29

2.62

2.18

2.21

2.02

  Ser

1.9

1.45

1.16

1.2

1.19

  Tyr

1.63

1.12

0.99

1.02

0.97



 

Table 2. Standardized ileal digestibility (SID) by growing pigs of crude protein and amino acids in  soybean meal (SBM), high protein canola meal (CM-HP), conventional canola meal (CM-CV), and canola meal processed at high or low temperatures (CM-HT and CM-LT, respectively) 

 

Ingredient

 

Item

SBM

CM-HP

CM-HT

CM-LT

CM-CV

P-value

  CP, %

87.1a

73.9b

73.5b

71.4b

71.1b

< 0.05

Indispensable AA, %

  Arg

95.5a

82.0b

84.8b

84.5b

84.1b

< 0.05

  His

89.0a

80.8b

80.7b

80.6b

78.2b

< 0.05

  Ile

89.5a

74.4b

75.3b

74.6b

72.4c

< 0.05

  Leu

88.0a

76.2b

77.3b

75.9b

76.2b

< 0.05

  Lys

86.2a

76.1b

71.8c

71.6c

64.3d

< 0.05

  Met

89.4a

83.0b

82.3b

81.6b

82.6b

< 0.05

  Phe

89.4a

75.8b

77.8b

76.2b

76.7b

< 0.05

  Thr

85.1a

69.4b

71.0b

68.6b

69.5b

< 0.05

  Trp

90.1a

84.9b

84.0b

80.7c

85.7b

< 0.05

  Val

86.2a

72.0b

72.8b

72.0b

69.2b

< 0.05

Mean

89.0a

76.5b

76.6b

77.9b

74.8b

< 0.05

Dispensable AA, %

  Ala

83.5a

75.5b

76.9b

75.2b

73.4b

< 0.05

  Asp

86.2a

71.1b

70.6b

68.9b

67.3b

< 0.05

  Cys

84.9a

74.9c

77.8b

75.1bc

68.1d

< 0.05

  Glu

89.5a

82.6b

83.8b

83.1b

82.0b

< 0.05

  Gly

85.9a

74.9b

78.0b

77.3b

74.7b

< 0.05

  Pro

125.21a

102.7c

104.6bc

110.4b

103.0bc

< 0.05

  Ser

89.5a

71.5b

72.9b

69.9b

72.9b

< 0.05

  Tyr

90.0a

75.6b

77.8b

76.4b

76.0b

< 0.05

Mean

90.8a

79.8bc

81.6b

80.8bc

77.7c

< 0.05

All AA

89.6a

77.7bc

79.3b

78.4bc

75.8c

< 0.05

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

This report is based on unpublished research by T. Maison and H. H. Stein.

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