Effects of physicochemical characteristics of feed ingredients on total tract digestibility of dry matter, energy, fiber, and protein by growing pigs

Dietary fiber is resistant to digestion in the small intestine, but is fermented in the large intestine and the resulting short chain fatty acids provide some energy to the pig. Fermentation occurs to a greater or lesser degree depending on the chemical and physical composition of the fiber; soluble fiber is generally fermented to a greater extent than insoluble fiber.

Bulk density, swelling capacity, water binding capacity, and viscosity of diets fed to pigs vary based on the types of fiber present in the diets. Therefore, an experiment was conducted to test the hypothesis that the physicochemical characteristics of feed ingredients are correlated with the concentrations of digestible energy (DE) and metabolizable energy (ME) and the apparent total tract digestibility (ATTD) of energy, dry matter (DM), and nutrients in corn, wheat, soybean meal (SBM), canola meal, distillers dried grains with solubles (DDGS), corn germ meal, copra meal, sugar beet pulp, solka floc, and pectin.

Materials and methods

Eighty growing barrows with an average initial body weight of 48.41 kg were allotted to a randomized complete block design with 4 blocks of 20 pigs and fed ten diets. Thus, there were 4 blocks and 2 replicate pigs per diet in each block for a total of 8 replicate pigs per diet. Two diets were based on corn or  wheat, one was a corn-SBM diet, and the remaining seven diets were based on a mixture of the corn-SBM basal diet and either canola meal, DDGS, corn germ meal, copra meal, sugar beet pulp, solka floc, or pectin. The ratio between corn and SBM was the same in all corn-SBM diets so that the contribution of corn and SBM to the diets containing the other fiber sources could be calculated. The DE, ME, and digestibility of nutrients in the other fiber sources were calculated by difference.

Diets were fed for 26 days. The initial 19 days were considered the adaptation period to the diet and the subsequent 5 days were used for urine and fecal sampling.

Bulk density, swelling, water binding capacity, and viscosity of all diets were measured in all diets (Table 2).

ATTD of GE and DE and ME concentration in ingredients

The ATTD of GE was greatest (P < 0.05) in corn, wheat, and SBM (Table 3). The ATTD of GE was greater (P < 0.05) in canola meal, DDGS, corn germ meal, copra expellers, and sugar beet pulp than in solka floc and pectin.

The concentration of DE and ME was greater (P < 0.05) in SBM than in all other ingredients. On an as-fed basis, the DE and ME of wheat did not differ from the values in SBM or copra expellers, and were greater (P < 0.05) than the DE and ME of corn, corn germ meal, DDGS, canola meal, sugar beet pulp, pectin, and solka floc.

On a dry matter basis, DE and ME in corn were not different from the De and ME in wheat andcopra expellers, but the DE and ME in canola meal, DDGS, sugar beet pulp, pectin, and solka floc were less (P < 0.05) than in the corn, wheat, and copra expellers.

Apparent total tract digestibility of DM, OM, and nutrients in ingredients

The ATTD of DM and OM was greater (P < 0.05) in wheat, corn, SBM, and pectin than in corn germ meal, copra expellers, sugar beet pulp, DDGS, canola meal, and solka floc (Table 4).

The ATTD of crude protein, acid hydrolyzed ether extract (AEE), NDF, ADF, TDF, and IDF were greater (P < 0.05) in pectin than in all other ingredients. Pectin also had the greatest concentration of soluble fiber as well as the highest swelling capacity, water binding capacity, and viscosity of all of the tested ingredients (P < 0.05 for all measurements).

The ATTD of NDF was greater (P < 0.05) in copra expellers than in wheat, SBM, corn, canola meal, and solka floc, but did not differ from the values for DDGS and corn germ meal. The ATTD of ADF was greater (P < 0.05) in SBM than in solka floc or corn, but did not differ from the values for sugar beet pulp, canola meal, DDGS, corn germ meal, or copra expellers. The ATTD of TDF was greater (P < 0.05) in sugar beet pulp than in corn germ meal, wheat, corn, canola meal, and solka floc, but did not differ from the values in SBM or copra expellers. The ATTD of IDF was greater (P < 0.05) in sugar beet pulp than in SBM, corn germ meal, corn, wheat, canola meal, DDGS, or solka floc, but did not differ from the values for copra expellers.

Correlation coefficients

The concentration of DE and the ATTD of DM in the ingredients were negatively correlated (P < 0.05) with concentrations of IDF and TDF (Table 5). The concentration of ME and the ATTD of GE were negatively correlated (P < 0.05) with TDF. The ATTD of crude protein was negatively correlated (P < 0.05) with the concentration of NDF, ADF, and IDF.

Swelling capacity of diets was positively correlated (P < 0.05) with ATTD of NDF, ADF, IDF, and TDF (Table 6.) Water binding capacity was positively correlated (P < 0.05) with ATTD of  IDF and TDF. Viscosity was positively correlated (P < 0.05) with ATTD of NDF, ADF, and IDF.

Key points

  • Physical properties such as bulk density, swelling capacity, water binding capacity, and viscosity may vary based on the types of fiber in the ingredient or diet.
  • Fiber content, particularly TDF, is negatively correlated with DE and ME.
  • Swelling capacity, water binding capacity, and viscosity can be used to predict the digestibility of fiber in vivo, but cannot be used to predict DE and ME.

Table 1. Analyzed nutrient composition of corn, wheat, soybean meal, canola meal, distillers dried grains with solubles, corn germ meal, copra expellers, sugar beet pulp, solka floc, and pectin, as-fed basis

 

Ingredient1

Item

Corn

Wheat

SBM

CM

DDGS

CGM

CE

SBP

SF

Pectin

GE, kcal/kg

3,722

3,797

4,109

4,267

4,537

4,179

4,713

3,740

3,957

3,384

DM, %

85.42

86.81

88.80

88.90

88.77

89.28

96.54

92.48

98.35

91.50

CP, %

6.56

10.80

46.90

40.52

25.52

23.91

21.65

7.27

0.71

1.68

AEE2, %

3.06

1.86

1.55

4.06

9.58

2.97

11.17

2.00

0.38

0.14

NDF, %

8.51

11.36

6.30

18.88

32.29

39.60

48.14

45.47

30.49

0.78

ADF, %

2.40

3.06

5.00

14.32

12.97

14.70

23.79

21.54

16.43

0.15

Lignin, %

0.47

0.69

0.16

7.39

2.29

4.29

5.14

2.46

ND

ND

Ash, %

1.05

1.61

6.78

7.14

5.91

2.61

5.63

6.96

0.04

1.62

OM, %

84.37

85.20

82.02

81.76

82.86

86.67

90.91

85.52

98.31

89.88

TDF3, %

10.76

11.40

17.84

26.42

34.66

39.78

43.84

48.54

93.31

51.69

   IDF, %

10.71

10.93

16.70

25.44

34.38

38.47

42.05

44.57

93.16

0.09

   SDF, %

0.06

0.47

1.14

0.98

0.29

1.31

1.79

3.97

0.15

51.60

1SBM = soybean meal; CM = canola meal; DDGS = distillers dried grains with solubles; CGM = corn germ meal; CE = copra expellers; SBP = sugar beet pulp; SF = solka floc.

2AEE = acid hydrolyzed ether extract.

3TDF = total dietary fiber; IDF = insoluble dietary fiber; SDF= soluble dietary fiber.

Table 2. Bulk density, swelling, water binding capacity (WBC), and viscosity of the diets

 

Diet

P-value

Item

Corn

Wheat

SBM

CM

DDGS

CGM

CE

SBP

SF

Pectin

Bulk density, g/L

668.09b

624.78d

787.01a

624.11d

533.17g

653.76c

571.82f

612.12e

254.02h

619.12de

<0.01

Swelling, L/kg DM

2.67g

3.00f

3.50e

4.05cd

4.14cd

3.90d

4.21c

4.54b

3.12f

6.00a

<0.01

WBC, g/g

1.23g

0.81h

1.51f

1.65e

1.62e

2.12c

2.09c

2.20b

1.71d

2.34a

<0.01

Viscosity, centipoise

0.98b

0.99b

1.01b

1.01b

1.02b

0.97b

1.00b

1.37b

0.99b

2.73a

<0.01

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

Table 3. Concentration of digestible and metabolizable energy and apparent total tract digestibility (ATTD) of GE in corn, wheat, soybean meal, canola meal, distillers dried grains with solubles, corn germ meal, copra expellers, sugar beet pulp, solka floc, and pectin, as-fed basis

 

Ingredient

P-value

Item

Corn

Wheat

SBM

CM

DDGS

CGM

CE

SBP

SF

Pectin

Ingredients

 

 

 

 

 

 

 

 

 

 

 

  ATTD of GE, %

86.8a

90.0a

88.4a

66.9cd

68.7c

74.5b

78.9b

75.4b

59.9e

62.3de

<0.01

  DE, kcal/kg

3,239cd

3,395bc

3,925a

2,742f

3,033e

3,037de

3,571b

2,705f

992h

2,328g

<0.01

  DE, kcal/kg of DM

3,786b

3,910b

4,409a

3,091d

3,419c

3,395c

3,687b

2,928d

1,469f

2,563e

<0.01

  ME, kcal/kg

3,174c

3,328bc

3,828a

2,517e

2,902d

2,923d

3,464b

2,657e

963g

2,179f

<0.01

  ME, kcal/kg of DM

3,714bc

3,835b

4,312a

2,830e

3,267d

3,273d

3,589c

2,874e

978g

2,381f

<0.01

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

Table 4. Apparent total tract digestibility (ATTD) of DM, OM, CP, acid hydrolyzed ether extract (AEE), NDF, ADF, total dietary fiber (TDF), insoluble dietary fiber (IDF), and soluble dietary fiber (SDF) in ingredients

 

Ingredient

-value

Item, %

Corn

Wheat

SBM

CM

DDGS

CGM

CE

SBP

SF

Pectin

DM

88.9a

90.2a

89.5a

66.5cd

69.6c

78.1b

80.0b

79.0b

61.8d

86.4a

<0.01

OM

90.6a

92.1a

90.8a

74.3c

74.9c

82.3b

84.4b

84.8b

68.4d

91.7a

<0.01

CP

77.9c

87.2b

91.7b

76.6c

80.0c

64.3d

67.8d

16.0f

30.6e

116.4a

<0.01

AEE

32.5d

59.4c

-4.4e

52.8c

60.9c

47.3c

87.2b

52.0c

75.7b

105.5a

<0.01

NDF

50.8e

68.7cd

66.5d

38.0e

73.1bcd

80.3bcd

83.6b

82.8bc

48.2e

116.7a

<0.01

ADF

60.5d

60.2d

84.9b

69.9bcd

75.1bcd

69.4bcd

78.9bcd

81.6bc

63.3cd

116.6a

<0.01

TDF

55.9de

61.3d

83.5bc

53.9e

53.6e

78.0c

82.3bc

86.9b

42.5f

97.5a

<0.01

   IDF

53.5d

59.8d

77.7c

53.7d

56.7d

78.3c

82.5bc

88.5b

44.5e

119.6a

<0.01

   SDF

103.3

107.5

99.7

53.8

105.0

96.5

208.3

-44.8

93.0

86.5

0.06

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

Table 5. Correlation coefficients between the concentration of fiber, concentration of DE and ME, and apparent total tract digestibility (ATTD) of DM and nutrients in ingredients

 

Correlation coefficient

Item

NDF

ADF

IDF

SDF

TDF

DE

ME

ATTD of DM

ATTD of GE

ATTD of CP

NDF

1

0.94***

0.65**

-0.43

0.43

-0.1

-0.09

-0.49

-0.2

-0.73**

ADF

 

1

0.71**

-0.43

0.49

-0.17

-0.17

-0.61*

-0.29

-0.75**

IDF

   

1

-0.41

0.81***

-0.65**

-0.63*

-0.77***

-0.48

-0.79***

SDF

     

1

0.2

-0.25

-0.27

0.24

-0.43

0.5

TDF

       

1

-0.86***

-0.85***

-0.68**

-0.80***

-0.53

DE

         

1

1.00***

0.67**

0.81***

0.43

ME

           

1

0.69**

0.84***

0.39

ATTD of DM

             

1

0.76**

0.51

ATTD of GE

               

1

0.18

ATTD of CP

 

 

 

 

 

 

 

 

 

1

* P < 0.10; ** P < 0.05; *** P < 0.01

Table 6. Correlation coefficients between the physical characteristics of  diets, concentration of DE and ME in ingredients, and apparent total tract digestibility (ATTD) of nutrients in ingredients

 

Correlation coefficient

Item

Bulk

Swelling

WBC

Viscosity

DE

ME

ATTD of NDF

ATTD of ADF

ATTD of IDF

ATTD of TDF

Bulk

1

0.11

-0.01

0.48

0.15

0.14

0.31

0.49

0.38

0.37

Swelling

 

1

0.89***

0.62*

-0.08

-0.09

0.75**

0.80***

0.89***

0.84***

WBC

   

1

0.3

-0.21

-0.2

0.48

0.57*

0.67**

0.68**

Viscosity

     

1

-0.21

-0.23

0.92***

0.86***

0.79***

0.58*

DE

       

1

1.00***

-0.04

-0.02

0.15

0.36

ME

         

1

-0.05

-0.04

0.14

0.36

ATTD of NDF

           

1

0.89***

0.91***

0.76**

ATTD of ADF

             

1

0.90***

0.78***

ATTD of IDF

               

1

0.95***

ATTD of TDF

 

 

 

 

 

 

 

 

 

1

* P < 0.10; ** P < 0.05; *** P < 0.01

This report is based on unpublished research by Diego Navarro and Hans H. Stein.

Authors: 
Publication Type: