Excessive heat treatment of double-low rapeseed meal reduces not only amino acid digestibility but also concentrations of metabolizable energy when fed to growing pigs

Double-low rapeseed meal (RSM) is currently used as a protein ingredient in animal diets. Heat treatment of RSM at varying processing conditions removes the residual hexane and efficiently reduces the glucosinolate content. However, variations in heat processing temperatures and duration of heat treatment may result in Maillard reactions, resulting in the formation of sugar-amino acid complexes. Maillard reaction products result in reduced standardized ileal digestibility (SID) of amino acids (AA), with Lys being the most sensitive AA. However, there is limited information about how heating affects the concentration of digestible energy (DE) and metabolizable energy (ME). Therefore, the objective of this experiment was to test the hypothesis that both the degree of heating and the time that heat is applied will affect the concentration of DE and ME and the SID of AA in double-low RSM fed to growing pigs.

 

Materials and Methods

Nine sources of RSM were used in the study. A conventional double-low RSM was either not autoclaved or autoclaved following one of 8 treatments: 110ºC for 15 or 30 min or 150ºC for 3, 6, 9, 12, 15, or 18 min. These 9 sources of RSM were used in 2 experiments.

 

Exp.1. Energy digestibility and concentrations of DE and ME

A corn-diet and 9 diets based on corn and each of the 9 sources of RSM were prepared. Thus, there were 10 diets in the experiment. Twenty growing barrows with an average initial BW of 21.23 ± 1.23 kg were randomly allotted to the 10 diets in a replicated 10 × 4 Youden Square with 10 diets and 4 periods. Thus, there were 2 pigs per diet in each period for a total of 8 replicate pigs per diet. Pigs were housed individually in metabolism crates that were equipped with a self-feeder, a nipple waterer, and a slatted floor. Urine and feces were collected for 5 d, and after determination of gross energy concentrations in diets, urine, and feces, concentrations of DE and ME in each source of RSM were calculated.

 

Exp. 2. Amino acid digestibility

Twenty growing barrows with an average initial BW of 69.81 ± 5.71 kg had a T-cannula installed in the distal ileum. Pigs were allotted to a replicated 10 × 4 Youden square design with 10 diets and four 7-day periods in each square. Pigs were placed in individual pens (1.2 by 1.5 m) that were equipped with a self-feeder, a nipple waterer, and a slatted tri-bar floor. The 10 diets included, a N-free diet and one diet containing each of the 9 sources of RSM as a sole source of AA, as described on Exp.1. Ileal digesta were collected on d 6 and 7 of each 7-d period. At the conclusion of the experiment, all sources of RSM, all diets, and all ileal digesta samples were analyzed for AA and values for the SID of AA in each source of RSM were calculated. 

 

Results

Exp.1. Energy digestibility and concentrations of DE and ME

There were no differences for ATTD of DM and GE, DE, and ME, and DE and ME on a DM basis between the conventional RSM and RSM autoclaved at 110ºC (Table 1). However, there was a decrease (quadratic, P < 0.05) in ATTD of DM and GE, and concentrations of DE, and ME in RSM if RSM was autoclaved at150ºC.

 

Exp. 2. Amino acid digestibility

The SID of CP and all AA was less (P < 0.01) if RSM was autoclaved at 150ºC than at 110ºC, but there was no differences between RSM without heat treatment and RSM that was heat treated at 110ºC (Table 2). The SID of CP and all AA decreased (quadratic, P < 0.01) as the duration of heat treatment increased at 150ºC.

 

Key points

  • Autoclaving of RSM at 110ºC for 15 or 30 min does not affect the ATTD of GE, DE and ME.
  • Digestibility of AA, and DE and ME, are reduced if RSM is autoclaved at 150ºC and the longer the duration of autoclaving is the more the SID of AA and DE and ME are reduced.
  • These results indicate that if crushing plants can avoid heating RSM to more than 110ºC during processing, the risk of over-heating is limited.

 

Table 1 Apparent total tract digestibility (ATTD) of GE, DM, and concentration of DE and ME in corn and rapeseed meal heat treated1, as-fed basis, Exp. 1

Item

Corn

RSM2

Heat treatment temperature

 

Contrast P-value

110°С

150°С

RSM

vs.

110°С

110°С

 vs.

150°С

At

110°С

At

150°С

Duration (min):

15

30

3

6

9

12

15

18

SEM

Linear

Linear

Quadra

tic

ATTD of GE, %

92.2

75.6

77.1

75.5

69.0

72.7

63.7

65.1

65.2

62.6

2.51

0.82

<0.001

0.65

0.93

0.001

ATTD of DM, %

93.5

73.3

75.8

73.7

67.8

71.2

63.1

64.1

64.6

62.1

2.31

0.60

<0.001

0.42

0.98

0.001

DE, kcal/kg

3,530

3,161

3,239

3,220

2,919

3,147

2,731

2,788

2,793

2,737

104

0.58

<0.001

0.57

0.95

0.004

ME, kcal/kg

3,457

2,873

3,013

3,017

2,720

2,936

2,508

2,619

2,547

2,458

114

0.28

<0.001

0.34

0.41

0.02

DE, kcal/kg DM

4,000

3,425

3,506

3,784

3,171

3,410

2,960

3,023

3,016

2,967

113

0.60

<0.001

0.59

0.90

0.003

ME, kcal/kg DM

3,918

3,113

3,262

3,264

2,955

3,182

2,719

2,839

2,750

2,665

123

0.30

<0.001

0.35

0.38

0.01

1Data are least squares means of 8 observations per treatment.

2RSM = rapeseed meal not autoclaved.

 

Table 2. Standardized ileal digestibility (%) of CP and AA in rapeseed meal (RSM) heat treated1,2, Exp. 2

Item

Control3

Heat treatment temperature

 

Contrast P-value

110°С

150°С

Control

vs.

110°С

110

°С

 vs.

150°С

110°С

150 °С

Duration (min):

15

30

3

6

9

12

15

18

SEM

Linear

Linear

Quadra

tic

CP

73.4

71.6

73.9

64.2

56.5

44.4

46.3

44.2

28.7

2.34

0.820

<0.001

0.580

0.023

<0.001

Indispensable AA

Arg

87.9

87.2

88.1

83.0

77.1

65.6

69.5

64.9

51.6

2.45

0.925

<0.001

0.811

0.001

<0.001

His

84.3

82.5

83.8

79.0

74.9

66.1

67.2

65.7

54.8

1.47

0.476

<0.001

0.327

0.001

<0.001

Ile

73.8

73.1

73.4

65.5

60.1

51.9

52.9

51.7

35.1

1.43

0.750

<0.001

0.741

0.002

<0.001

Leu

78.2

77.4

77.4

69.7

66.0

59.3

60.6

59.4

45.5

1.29

0.600

<0.001

0.654

0.025

<0.001

Lys

76.8

70.8

73.3

59.9

45.7

25.7

25.8

21.6

-0.49

2.69

0.095

<0.001

0.070

0.001

<0.001

Met

50.3

44.7

50.3

36.5

23.3

10.5

9.4

9.5

-22.1

3.85

0.546

<0.001

0.293

0.012

<0.001

Phe

76.6

76.2

76.2

68.7

66.2

61.2

62.0

60.5

50.1

1.73

0.840

<0.001

0.861

0.218

<0.001

Thr

69.9

66.2

69.1

59.6

54.9

46.6

47.9

47.0

30.1

2.09

0.336

<0.001

0.181

0.096

<0.001

Trp

72.1

69.6

71.6

63.7

61.0

55.7

56.7

58.1

44.4

1.77

0.506

<0.001

0.332

0.521

<0.001

Val

73.3

70.6

72.9

65.7

60.4

52.2

52.9

51.6

36.6

1.87

0.489

<0.001

0.293

0.008

<0.001

Dispensable AA

Ala

74.3

73.1

73.7

64.9

58.3

48.0

51.2

48.0

32.9

2.09

0.689

<0.001

0.651

0.028

<0.001

Asp

72.3

68.4

69.4

54.9

43.7

32.4

35.0

33.6

12.2

2.88

0.274

<0.001

0.280

0.476

<0.001

Cys

74.2

70.7

72.7

58.0

48.5

33.4

34.2

31.4

7.8

2.68

0.418

<0.001

0.332

0.015

<0.001

Glu

84.7

83.5

84.9

78.9

74.2

65.7

67.6

65.5

54.4

1.45

0.714

<0.001

0.485

0.002

<0.001

Gly

76.8

79.5

74.4

65.6

55.9

42.3

46.5

44.5

25.5

4.34

0.985

<0.001

0.654

0.241

<0.001

Pro

97.4

98.0

96.8

82.4

67.9

34.1

55.7

35.1

36.9

11.03

0.999

<0.001

0.964

0.754

<0.001

Ser

72.3

69.1

71.0

61.8

57.2

48.5

50.6

49.1

34.3

2.01

0.324

<0.001

0.227

0.186

<0.001

1Data are least squares means of 8 observations per treatment.

2Values for standardized ileal digestibility were calculated by correcting apparent ileal digestibility values for basal endogenous losses. Basal endogenous losses were determine using pigs fed the N-free diet as (g/kg DMI): CP, 16.09; Arg, 0.47; His, 0.15 Ile, 0.28; Leu, 0.45; Lys, 0.36; Met, 0.29; Phe, 0.25; Thr, 0.54; Trp, 0.14; Val 0.41; Ala, 0.60; Asp, 0.76; Cys, 0.21; Glu, 0.94; Gly, 1.50; Pro, 4.50; and Ser, 0.53.

3Rapeseed meal not autoclaved.

 

 

 

 

 

 

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