Amino acid and energy digestibility of an enhanced torula yeast and fish meal fed to weanling pigs

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Yeast may be used instead of fish meal or other animal protein sources in diets for weanling pigs and there are several yeast proteins available. A newly developed enhanced torula yeast is derived from forestry by-products, and therefore, has a lower carbon-footprint compared with other yeast products. This enhanced torula yeast has an improved amino acid (AA) profile compared with traditional fermentation products, but at this time no data for the nutritional value of enhanced torula yeast fed to weanling pigs have been published. Therefore, 2 experiments were conducted to test the hypothesis that the AA and energy values of enhanced torula yeast is not different from that of fish meal. In Exp. 1, the apparent ileal digestibility (AID) and the standardized ileal digestibility (SID) of AA were determined, whereas Exp. 2 was designed to determine the concentration of digestible energy (DE) and metabolizable energy (ME) in both enhanced torula yeast and fish meal.

 

Experimental Procedures

The enhanced torula yeast was sourced from Arbiom Inc. (Durham, NC) and a commercial source of fish meal was also used (Table 1). Both ingredients were used in the two experiments.

In Exp. 1, 6 weanling barrows (initial BW: 11.7 ± 0.4 kg) were equipped with a T-cannula in the distal ileum and allotted to a replicated 3 × 3 Latin square design with 3 diets and 3 periods for a total of 6 replicate pigs per diet. Two cornstarch-based diets were formulated using enhanced torula yeast or fish meal as the only AA-contributing ingredients in each diet and a N-free diet was used to measure basal endogenous losses of AA. In each period, diets were fed for 7 days with ileal digesta being collected for 8 h on days 6 and 7. The ileal digesta were analyzed for AA to calculate AID and SID of all AA.

In Exp. 2, 24 barrows (initial BW: 14.4 ± 1.1 kg) were placed in individual metabolism crates and allotted to a completely randomized design with 3 diets and 8 replicate pigs per diet. The dietary treatments included a corn-based diet and 2 diets based on a mixture of corn and enhanced torula yeast or fish meal. Feces and urine samples were collected using the marker to marker approach with 5-d adaptation and 4-d collection periods. Samples of diets, feces, and urine were analyzed for gross energy to calculate concentrations of DE and ME in each ingredient.

 

Results

The AID and SID of AA in enhanced torula yeast were greater (P < 0.01) than in fish meal (Table 2), but there was no difference in the ATTD of GE between enhanced torula yeast and fish meal (Table 3). The concentration of DE in enhanced torula yeast tended (P < 0.10) to be greater than in fish meal, but if calculated on a DM-basis, no difference in the concentration of DE between enhanced torula yeast and fish meal was observed. The concentration of ME was also not different between the 2 ingredients.

 

Key points

  • The AID and SID values for AA are greater in enhanced torula yeast than in fish meal.
  • The concentration of DE and ME in enhanced torula yeast yeast is not different from fish meal

 

Table 1. Analyzed composition of ingredients (as-fed basis)

 

Ingredient

Item

Enhanced torula yeast

Fish meal

DM, %

95.69

91.20

GE, kcal/kg

4,600

4,320

CP, %

52.37

64.17

Ash, %

11.53

20.01

Indispensable AA, %
  Arg

2.39

3.60

  His

0.91

1.17

  Ile

2.31

2.55

  Leu

3.42

4.22

  Lys

3.45

4.51

  Met

0.58

1.61

  Phe

2.10

2.44

  Thr

2.35

2.40

  Trp

0.62

0.55

  Val

2.79

2.94

Dispensable AA, %
  Ala

3.33

3.98

  Asp

4.32

5.33

  Cys

0.49

0.47

  Glu

8.07

7.83

  Gly

2.27

4.74

  Pro

1.55

2.94

  Ser

1.97

2.04

  Tyr

1.67

1.68

  Total AA

44.59

55.00

Lys: CP ratio

6.59

7.03

 

 

Table 2. Apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA in enhanced torula yeast and fish meal fed to weanling pigs.
 

AID

SID1

 

Ingredient

Ingredient

Item

Enhanced torula yeast

Fish meal

SEM

P-value

Enhanced torula yeast

Fish meal

SEM

P-value

Indispensable AA, %

  Arg

92.6

78.3

1.76

< 0.001

99.4

83.0

1.76

< 0.001

  His

91.0

69.8

1.07

< 0.001

96.3

74.3

1.07

< 0.001

  Ile

90.2

71.5

0.92

< 0.001

93.9

75.1

0.92

< 0.001

  Leu

91.3

72.9

0.88

< 0.001

95.3

76.3

0.88

< 0.001

  Lys

91.7

73.1

1.13

< 0.001

95.2

76.0

1.13

< 0.001

  Met

90.3

74.8

0.99

< 0.001

94.5

76.3

0.99

< 0.001

  Phe

90.6

69.8

0.91

< 0.001

94.8

73.7

0.91

< 0.001

  Thr

78.8

65.6

1.13

< 0.001

86.2

73.4

1.13

< 0.001

  Trp

92.1

79.0

0.91

< 0.001

97.0

84.3

0.91

< 0.001

  Val

86.3

67.8

1.09

< 0.001

92.4

73.9

1.09

< 0.001

 Mean

89.5

72.3

0.95

< 0.001

94.5

76.6

0.95

< 0.001

Dispensable AA, %

  Ala

90.0

71.7

1.23

< 0.001

94.4

75.7

1.23

< 0.001

  Asp

87.1

57.6

0.96

< 0.001

92.0

61.8

0.96

< 0.001

  Cys

74.6

55.4

1.53

< 0.001

87.9

68.5

1.53

< 0.001

  Glu

92.1

72.2

0.72

< 0.001

94.9

75.3

0.72

< 0.001

  Gly

79.3

66.2

3.39

0.008

99.5

76.2

3.39

< 0.001

  Ser

81.9

65.2

1.39

< 0.001

89.2

72.8

1.39

< 0.001

  Tyr

89.8

67.7

0.95

< 0.001

94.1

72.3

0.95

< 0.001

 Mean

84.9

65.1

1.33

< 0.001

93.2

71.8

1.33

< 0.001

All AA

87.6

69.3

1.10

< 0.001

93.9

74.6

1.10

< 0.001

1Values for SID were calculated by correcting the values for AID for basal ileal endogenous losses (n = 6). Basal ileal endogenous losses were determined (g/kg of dry matter intake) as CP, 16.14; Arg, 0.57; His, 0.18; Ile, 0.31; Leu, 0.49; Lys, 0.45; Met, 0.09; Phe, 0.32; Thr, 0.64; Trp, 0.11; Val, 0.62; Ala, 0.54; Asp, 0.77; Cys, 0.25; Glu, 0.86; Gly, 1.61; Ser, 0.52; and Tyr, 0.23.

Table 3. Apparent total tract digestibility (ATTD) of gross energy (GE) and concentration of DE and ME in enhanced torula yeast and fish meal fed to weanling pigs

Item

Enhanced torula yeast

Fish meal

SEM

P-value

ATTD of GE, %

88.88

86.35

1.60

  0.188

As-fed basis

    DE, kcal/kg

3850

3689

65.80

   0.059

    ME, kcal/kg

3479

3291

74.76

   0.119

DM basis

    DE, kcal/kg

4023

4045

70.83

   0.783

    ME, kcal/kg

3636

3609

80.20

   0.820

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