SIAAD of meals reported for laying hens, broilers

SIAAD of meals reported for laying hens, broilers

*Dr. William A. Dudley-Cash is a poultry and fish nutritionist and has his own consulting firm in Modesto, Cal. To expedite answers to questions concerning this column, please direct inquiries to Feedstuffs, Bottom Line of Nutrition, 7900 International Dr., Suite 650, Bloomington, Minn. 55425, or email [email protected]

STANDARDIZED ileal amino acid digestibility (SIAAD) is a measure of the digestibility of amino acids in a feed ingredient.

Digestible amino acids are the best measure of the amino acid value of ingredients. Most commercial nutritionists have adopted the use of digestible amino acid values in their feed formulations. Unfortunately, the use of digestible amino acid values is handicapped by a lack of sufficient digestibility information for all of the feed ingredients the nutritionist wants to use.

Also, there are questions about the applicability of digestibility values determined with one species, strain or age of poultry to poultry of another species, strain or age.

S. Adedokun et al. (2014) reported a study designed to determine the SIAAD of seven meat and bone meal (MBM) and three soybean meal (SBM) samples in Ross 708 broilers and Hy-Line W36 laying hens.

The ingredient samples were sourced from the Midwest and Mideast regions of the U.S. in 2010. Each of the 10 feed ingredients was added to a semi-purified experimental diet as the sole source of crude protein in order to provide 20% crude protein in the diet.

 

Experimental diets

The experimental diets are described in Table 1, with the top line showing the analyzed crude protein content of the test ingredients. The MBM samples varied in crude protein content from 47.3% to 55.9%. To achieve 20% crude protein in the experimental diet, the levels in the MBM samples varied from 35.8% to 42.4%, and the level of corn starch was adjusted accordingly.

SBM samples 1, 2 and 3 analyzed 47%, 48% and 45% crude protein, respectively. However, for formulation of the SBM experimental diets, the value of 46.0% crude protein was applied for all three samples, and the level of SBM included in the diet was the same (44.2%), as was the level of dextrose (44.4%), in each of the three SBM experimental diets.

In addition to the 10 diets for the 10 ingredient samples, a nitrogen-free diet (NFD) was also formulated and fed in each experiment.

Chromic oxide was added to each experimental diet as an indigestible marker. The same diet batch was fed to broilers and laying hens. The analyzed crude protein, dry matter and total amino acid content of the 10 experimental diets are shown in Table 2. The NFD diet is not listed in Table 2 because it contained no crude protein or amino acids.

 

Broiler design

All 10 feed ingredients were evaluated in 21-day-old broilers. A total of 528 day-old broiler chicks were housed in cages and fed a standard broiler diet from 0 to 16 days of age. At 16 days, the broilers were allotted to treatments using a randomized complete block design with six replicate cages of eight birds per cage and then were fed the 11 experimental diets (10 ingredient diets and one NFD) from 16 to 21 days of age.

At 21 days of age, the birds were euthanized using carbon dioxide asphyxiation. Digesta was collected from the entire ileum of all birds within a cage by flushing the ileum with distilled water. The ileum was defined as that portion of the small intestine from Meckel's diverticulum to about 5 mm proximal to the ileo-cecal-colonic junction.

The digesta from each cage was pooled, frozen and stored at -20 degrees C. The stored samples were subsequently freeze-dried and ground with a coffee grinder.

 

Laying hen design

The seven MBM samples were evaluated in 288 laying hens that were 30 weeks old. The 144 laying hens used to evaluate the three SBM samples were 50 weeks old.

In each experiment, the experimental diets (seven or three ingredient diets plus the NFD) were fed to six replicates of six birds per replicate (each replicate consisted of three adjacent cages of two birds per cage) for five days. The ileal contents of each replicate were harvested, pooled and prepared in the same manner described for the broilers.

The details of the analytical methods employed are contained in the original paper. The amino acid digestibility values were "standardized" by correcting for basal ileal endogenous amino acid (EAA) losses using the information from the NFD.

 

Ileal EAA flow

The ileal EAA flow from the NFD was used to standardize the digestibility of the amino acids. The EAA flow was measured as milligrams of amino acid per kilogram of dry matter intake. A summary of the results of the measured EAA flow is shown in Table 3. The complete results for each individual amino acid are in the original paper.

The results summarized in Table 3 show that the EAA flow was very similar when broilers were compared with laying hens that were either 30 or 50 weeks of age.

On average, the EAA flow was markedly higher for the nonessential amino acids than the mean of the essential amino acids. Methionine had the lowest EAA flow of all amino acids for broilers and layers, while cysteine had the lowest EAA flow for all nonessential amino acids.

In the comparisons of EAA values between broilers and laying hens (30 and 50 weeks old), the standard deviations were large, representing about 25% of the measured values. The large standard deviations may indicate either a large variation in actual values between birds or some difficulty in measuring EAA.

 

SIAAD

Table 4 shows a summary of the SIAAD values for the seven MBM samples. The details for all of the amino acids are contained in the original paper.

SIAAD values were higher for broilers than laying hens for six of the seven MBM samples. The SIAAD values were significantly higher for broilers for samples 3, 4, 5 and 7, while samples 2 and 6 were numerically higher for broilers. Only sample 1 was numerically higher for laying hens.

Taken individually, virtually all of the SIAAD values for the essential amino acids were higher for broilers than laying hens for samples 2-7. The only exceptions were leucine, cysteine and threonine in MBM sample 6, which was uniquely identified as a porcine MBM. The SIAAD values were consistently higher for the essential amino acids compared to the nonessential amino acids.

Cysteine consistently had the lowest SIAAD value of all of the amino acids for both broilers and laying hens — consistently at or below 50%. In the case of MBM sample 6, the measured SIAAD value was only 11.5%. This extremely low SIAAD value may have been associated with sample 6 being a porcine MBM, or it may simply indicate that MBM sample 6 had been severely damaged during production.

Table 5 shows a summary of the SIAAD values for the three SBM samples, which were consistently higher than the SIAAD values for MBM.

When comparing laying hens with broilers, there were no significant differences; however, as observed with the MBM samples, the broiler values for SIAAD were consistently numerically higher than the laying hen values. Also, the SIAAD values for cysteine were the lowest of all amino acids in every sample.

In the case of MBM, the SIAAD values for essential amino acids were consistently higher than for the nonessential amino acids in the same sample. That was also the case for the SBM samples, but the differences were smaller.

 

Broiler growth

The broiler growth performance from 16 to 21 days of age for the 10 ingredient samples tested is shown in Table 6. There were no significant differences in weight gain or feed-to-gain ratio for the three samples of SBM. There were significant differences between the seven samples of MBM, which tended to correspond with the SIAAD values (particularly the values for cysteine) determined for these samples.

These results tend to validate the importance of the SIAAD determinations.

 

Comments

This research shows that there are large differences in amino acid digestibility between ingredients (SBM versus MBM), among samples (sources) of the same ingredient (MBM), for different target animals (broilers versus laying hens) and, clearly, among amino acids in the same ingredient.

I was particularly struck by the consistently high values for the EAA flow of cysteine and by the consistently low SIAAD values for cysteine. These values may indicate that cysteine is uniquely subject to ingredient processing damage or that there are some problems with the procedures for determining the SIAAD value of cysteine.

Although there is still variation in the determination of amino acid digestibility, I believe the use of digestible amino acid values in feed formulation will significantly improve performance, consistency of performance and the economics of performance compared with the use of total amino acid values. Even the use of a poor set of digestible amino acid values is vastly superior to the use of the best set of total amino acid values.

The accurate measurement of EAA excretion is an important part of determining amino acid digestibility. The procedures described in this paper are the result of several years of research and publications by the senior author (and a hall-of-fame list of junior authors) designed to evaluate the best method of measuring amino acid digestibility. The reference list includes eight papers by Adedokun, including a review (2011).

Clearly, there is some unexplained variation that requires more research, but the authors believe that this is state of the art.

In addition to enabling better basic feed formulation, measuring digestible amino acid values is essential to evaluating other aspects of nutrition. Enzymes are an important example. The value of proteases, phytases, amylases and other enzymes is based on their ability to make more nutrients available, so evaluation of these feed additives must include an accurate determination of nutrient digestibility under a wide range of conditions.

 

The Bottom Line

This research shows that there are important differences in amino digestibility between ingredients, within ingredients and for broilers versus laying hens. The use of the best values for nutrient availability is essential for the improvement of practical feed formulations.

 

References

Adedokun, S., O. Adeola, C. Parsons, M. Lilburn and T. Applegate. 2011. Review: Factors affecting endogenous amino acid flow in chickens and the need for consistency in methodology. Poult. Sci. 90:1737-1748.

Adedokun, S., P. Jaynes, M. Abd El-Hack, R. Payne and T. Applegate. 2014. Standardized ileal amino acid digestibility of meat and bone meal and soybean meal in laying hens and broilers. Poult. Sci. 93:420-428.

 

1. Composition of experimental diets

Item, %

MBM

SBM

NFD

Crude protein

47.3-55.9

46.0

0.0

Ingredient

Test ingredient

35.8-42.4

44.20

Corn starch

44.6-51.2

17.90

Dextrose

0.0

44.40

64.00

Sodium bicarbonate

1.20

Potassium chloride

0.40

Magnesium oxide

0.07

Solkafloc1

5.00

5.00

Soybean oil

5.00

5.00

5.00

Vitamin/mineral premix

0.50

0.50

0.50

Monocalcium phosphate

1.90

1.90

Choline chloride

0.30

0.25

Limestone

1.00

1.30

Sodium chloride

0.20

 

Chromic oxide premix2

2.50

2.50

2.50

Total

100.00

100.00

100.02

1Purified cellulose.

2Prepared by mixing 1 g of chromic oxide with 4 g of corn starch.

 

2. Analyzed amino acid content of experimental diets (as-is basis)*

Item, %

MBM1

MBM2

MBM3

MBM4

MBM5

MBM6

MBM7

SBM1

SBM2

SBM3

Crude protein

20.2

20.4

19.2

21.1

19.6

18.9

19.3

21.8

22.0

20.9

Dry matter

96.4

96.8

97.2

97.1

97.2

96.5

92.8

91.6

91.2

91.2

Amino acid, %

Arginine

1.34

1.32

1.24

1.37

1.36

1.32

1.33

1.57

1.60

1.50

Isoleucine

0.57

0.62

0.54

0.60

0.51

0.52

0.54

0.99

0.98

0.92

Leucine

1.22

1.32

1.11

1.26

1.09

1.11

1.20

1.67

1.70

1.56

Lysine

0.96

1.07

0.90

1.03

0.92

0.96

0.95

1.22

1.18

1.09

Methionine

0.28

0.29

0.26

0.29

0.26

0.26

0.26

0.29

0.27

0.27

Methionine + cysteine

0.44

0.47

0.44

0.44

0.43

0.48

0.49

0.58

0.55

0.55

Cysteine

0.16

0.18

0.18

0.15

0.17

0.21

0.24

0.30

0.28

0.28

Threonine

0.64

0.69

0.60

0.66

0.60

0.60

0.63

0.84

0.86

0.79

Valine

0.81

0.88

0.76

0.85

0.75

0.76

0.82

1.03

1.03

0.96

*Amino acids were not detected in the nitrogen-free diet.

Note: MBM6 was porcine MBM.

 

3. Ileal endogenous amino acid flow

 

 

-Laying hens-

 

Essential amino acids*

Broilers

30 weeks old

50 weeks old

SD

Mean

392

363

403

93

Range

107-608

111-547

112-624

35-142

Methionine

107

111

112

35

Nonessential amino acids

Mean

539

520

573

123

Range

240-926

218-931

261-999

45-251

Cysteine

240

218

261

45

*Ileal EAA flow, mg/kg of dry matter intake.

 

4. Comparison of SIAAD of MBM samples, laying hens vs. broilers

 

-Essential amino acids-

-Nonessential amino acids-

MBM sample

Mean

Range

Methionine

Mean

Range

Cysteine

1: Hen

72.7

68.3-78.7

72.8

64.5

51.9-72.3

51.9

 Broiler

71.6

66.3-78.0

71.8

62.0

38.5-74.1

38.5

 SEM*

3.68

3.27-4.06

3.61

4.97

4.08-5.65

5.52

2: Hen

63.2

57.9-69.2

60.5

56.4

40.7-66.8

40.7

 Broiler

70.8

64.8-76.2

69.3

61.9

29.7-75.5

29.7

 SEM

3.55

2.43-4.34

4.34

3.03

2.10-4.10

4.09

3: Hen

73.9b

70.0-77.5

75.9

65.5b

47.4-73.6

47.4

 Broiler

81.9a

77.0-85.8

82.3

73.5a

51.9-82.7

51.9

 SEM

1.99

1.75-2.45

1.83

2.46

1.81-4.57

4.57

4: Hen

50.1b

42.2-57.0

47.6

40.7b

21.5-53.5

21.5

 Broiler

67.0a

62.1-73.7

65.0

61.0a

38.4-72.4

38.4

 SEM

3.10

2.66-3.77

3.12

3.58

2.56-6.41

6.41

5: Hen

65.4b

58.7-69.5

68.1

52.5b

44.0-61.7

44.0

 Broiler

73.0a

66.6-75.6

75.3

61.0a

41.5-73.6

41.5

 SEM

2.02

1.58-2.64

1.78

2.92

2.12-4.41

4.41

6: Hen

70.1

60.3-78.3

74.8

58.5

25.9-73.6

25.9

 Broiler

70.3

59.6-78.5

75.4

57.8

11.5-77.0

11.5

 SEM

2.01

1.64-2.54

1.92

2.27

1.51-4.25

4.25

7: Hen

74.8b

67.3-81.5

77.5

65.1b

48.2-74.8

48.2

 Broiler

81.8a

74.8-88.6

83.1

73.0a

48.6-84.3

48.6

 SEM

1.58

1.35-1.98

1.35

1.90

1.56-3.10

3.10

a,bMeans within ingredient were significantly different (P < 0.05).

*SEM = standard error of means.

 

5. Comparison of SIAAD of SBM samples, laying hens vs. broilers

 

-Essential amino acids-

-Nonessential amino acids-

SBM sample

Mean

Range

Methionine

Mean

Range

Cysteine

1: Hen

87.6

81.5-92.3

87.7

84.5

76.2-90.5

76.2

 Broiler

90.7

87.4-92.8

92.3

88.7

85.4-91.8

85.4

 SEM

1.10

0.74-1.63

1.19

1.23

0.82-1.27

1.88

2: Hen

88.1

83.2-92.6

88.6

85.3

77.0-90.3

77.0

 Broiler

89.1

86.4-91.5

90.7

87.4

84.5-90.3

84.5

 SEM

1.13

0.84-1.44

1.17

1.18

0.91-1.59

1.59

3: Hen

88.0

82.8-92.3

87.0

86.1

78.7-91.3

78.7

 Broiler

90.9

87.7-93.2

92.5

89.3

87.2-92.1

87.2

 SEM

0.95

0.65-1.44

1.22

1.02

0.67-1.47

1.47

 

6. Broiler performance, 16-21 days of age

Test ingredient

Weight gain, g

Gain:feed

MBM1

157b

0.541b

MBM2

144bc

0.564b

MBM3

160ab

0.568b

MBM4

156bc

0.551b

MBM5

136ce

0.515b

MBM6

104d

0.444c

MBM7

176a

0.693a

SBM1

260

0.695

SBM2

257

0.711

SBM3

267

0.708

a,b,c,d,eMeans within a column with different superscripts are significantly different (P < 0.05).

 

 

Volume:86 Issue:18

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