Reducing crude protein in layer diets studied

Reducing crude protein in layer diets studied

*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, 5810 W. 78th St., Suite 200, Bloomington, Minn. 55439, or email [email protected]

TO alleviate the burden of elevated feed prices in recent years, several studies have focused on the development of dietary formulations aimed at reducing feed costs while maintaining production performance.

One of these strategies is based on formulating diets on an ideal protein basis while eliminating or reducing crude protein restrictions. The goal is to provide ideal levels of the essential amino acids for optimizing hen performance while minimizing excess amino acids. This is accomplished by reducing the crude protein content of the diet while supplementing any limiting essential amino acids with crystalline amino acids. With the increasing availability of a number of synthetic amino acids, this feeding strategy is becoming more attractive.

H. Burley and P. Patterson of Pennsylvania State University and M. Elliott of A & E Nutritional Services published a paper on the effect of a reduced-crude protein, amino acid-balanced diet on hen performance, production costs and ammonia emissions in a commercial laying hen flock.

Several university studies have shown that reducing the crude protein restriction while supplementing the essential amino acids can effectively maintain the egg production performance of laying hens.

The objective of the Burley et al. research was to determine if these results can be reproduced under commercial-scale conditions.

 

Materials, methods

A total of 50,760 Lohmann LSL Lite laying hens were obtained from a commercial pullet farm at 18 weeks of age and placed in an environmentally controlled, mechanically ventilated high-rise house that employed a deep-pit manure storage system.

The birds were housed in six rows, with 8,460 birds in each row. There were either seven or eight birds per cage, with a total of 1,128 cages per row in a back-to-back configuration. There were 564 cages in the front and an equal number of cages in the back of the row.

A chain feeder extended the length of the front cages, made a U-turn and extended the length of the back cages of each row. In this configuration, the front of the feed trough was at the feed hopper, the midpoint of the feed trough was at the distant point of the row and the end of the feed trough was, again, at the hopper end of the row, in front of the back cages.

Each of the six rows of cages was randomly assigned to one of three dietary treatments, with two rows per treatment.

The diets were fed to each of the treatment groups from 18 to 51 weeks of age (February to September). All lighting and management practices were in accordance with current recommendations for the breed. The flock owner was allowed to make minor adjustments in management as long as the adjustments applied to the entire flock and did not affect individual treatment groups.

 

Dietary treatments

There were three experimental treatment diets: a low-crude protein diet, a medium-crude protein diet and a control diet (Table 1). The control diet represented a typical commercial laying hen diet. The other two diets represented stepwise reductions in the crude protein requirement.

The experimental diets were formulated by Wenger's Feed Mill Inc. in Rheems, Pa. A commercial-type phase feeding program was employed, and the diets were least-cost formulated each week based on current ingredient prices and nutrient requirements.

Corn and soybean meal were the predominant feed ingredients in the diets, with corn averaging 52.37%, 51.08% and 49.14% and soybean meal averaging 10.02%, 11.59% and 17.39% for the low diets, medium diets and control diets, respectively, over the eight months of the trial.

All of the diets were formulated to meet the same ideal amino acid requirements, with adjustments made for the phase feeding. As the protein requirement was reduced from the control to the medium to the low diets, synthetic amino acids were added to meet the ideal amino acid requirements. The treatment diets were designed to be isocaloric and contained an average of 2,860 kcal/kg of metabolizable energy.

Once every four weeks, feed samples were collected at the front, middle and end of the feed trough from each cage row, resulting in six replicate feed samples for each diet and for each location along the feed trough at each sampling date. Feed samples were sent to Evonik-Degussa for analysis of dry matter, crude protein, lysine, methionine, methionine plus cysteine (total sulfur amino acids [TSAA]) and threonine.

Table 2 shows the average analyzed nutrient concentrations for the feed samples taken throughout the experiment for the control diet, medium diet and low diet.

The results showed a significant difference in crude protein content that reflected the design of the experiment. There was no significant difference in lysine, methionine or TSAA content, as was intended. The threonine content of the control diet was significantly higher than the other two diets. The researchers noted that this was the result of the greater crude protein restriction in the control diet.

There was a concern that particle size segregation from the beginning to the end of the feed track might change the nutrient content of the feed. The results of the nutrient analysis by location shown in Table 2 indicate that there was very little change in the nutrient content of the feed when comparing the front to the middle and the end of the feed trough.

The feed samples were also analyzed for particle size by separating 200 g fractions into 10 particle sizes using an AS 200 sieve shaker and nine USA Standard Testing sieves with openings ranging from 3,360 micrometers (sieve number 6) to 210 micrometers (sieve number 70). The average results for the sieve testing are shown in Table 3.

There were significantly fewer large particles in the control diet than the medium and low diets but significantly more medium-sized particles (sieves 16-40) in the control versus the medium and low diets.

The researchers suggested that the difference in particle size distribution reflects the distribution of corn and soybean meal in the three diets. Corn is generally of larger particle size, while soybean meal is mostly of smaller particle size compared with corn. The low diet contained significantly more fine particles (pan) than the control diet, which reflected the higher content of synthetic amino acids, according to the researchers.

The sieving results shown for the trough location indicate that there was no significant particle separation along the length of the feed trough.

 

Performance results

Once every four weeks, hens from a single cage at the front, middle and end of the feed trough for each cage row were weighed, resulting in six replicate cages of hen bodyweight for each dietary treatment and each location along the feed trough at each sampling date.

Once every four weeks, 15 eggs were collected at the front, middle and end of the feed trough in each cage row. The result was six replicate examples for each dietary treatment and for each location along the feed trough at each sampling date. Samples were taken to Penn State for interior egg quality analysis or to Wenger's feed mill for shell quality analysis.

The performance results by diet and feed trough location are shown in Table 4. There were no significant differences in bodyweight, egg weight, albumin height, Haugh unit, yolk color, shell strength or shell thickness that could be attributed to the experimental diets.

The performance results associated with location along the feed trough indicated that albumin height and Haugh units were significantly larger in the middle of the trough. The researchers suggested that this result might be associated with environmental differences. Because of the configuration of the experimental rows, the front and the end of the trough were both at one end of the row, while the middle of the trough was at the other end of the row.

Feed consumption and egg production results. Mean feed consumption and egg production results are shown in Table 5.

Weekly water intake and feed consumption increased from starting levels at 18 weeks of age and leveled off in a manner similar to that of a normal commercial flock, according to Burley et al.

Percent daily egg production increased after housing and then leveled off in a manner similar to a normal commercial flock, according to the researchers. Peak hen-day egg production was exceptional for all dietary treatments and occurred at 27 weeks of age. Typical commercial egg production for this breed of hen ranges from 92% to 95%.

Cumulative eggs per hen housed averaged 205 eggs across dietary treatments for this experiment, compared with an expected average of 195.1 cumulative eggs for this breed under commercial conditions. Burley et al. noted that both egg production and cumulative eggs per hen housed were similar across dietary treatments.

Mean weekly egg case weight increased from the lowest diet to the highest crude protein diet (Table 5). Hens fed the control diet reached the 20.41 kg case weight benchmark at 24 weeks of age, while hens fed the low diet and the medium diet needed one additional week to achieve this same case weight.

Mean weekly egg mass averaged 58.0 g across all dietary treatments, compared with 55.7 g for a typical commercial flock at 51 weeks of age. Egg mass also increased from the lowest to the highest crude protein diets. These observations suggest that lower dietary crude protein may lead to a lower egg weight on a commercial scale.

The most important and marketable eggs produced by commercial flocks are large Grade A eggs. Weekly percentages of these eggs for each dietary treatment were assessed. What is interesting is that greater percentages of large eggs were consistently observed in the low diet, followed by the medium diet and then the control diet (Table 5). Hens fed the medium diet and control diet produced lower percentages of large eggs because they were generating greater percentages of extra-large and jumbo eggs.

Average percentages of cracked, dirty and lost eggs were all greatest for the control diet versus the low and medium dietary treatments. The researchers suggested that these observations provide further evidence that hens fed higher-crude protein diets produce larger eggs, and larger eggs can have thinner shells that break more easily and result in higher percentages of cracked and lost eggs.

Manure composition and ammonia flux. An airflow recirculation portable flux chamber was used to measure ammonia flux every four weeks at representative locations on the surface of the manure directly beneath the front, middle and end locations along the feed trough of each cage row.

Every four weeks, 200 g of manure was collected from the pit of the house directly beneath the front, middle and end locations along the feed trough from each cage row. The manure was sampled from the surface of the pile to a depth of no greater than 10 cm in the same locations where ammonia flux was measured. The Agricultural Analytical Services Laboratory at Penn State analyzed all manure samples for percent dry matter, total nitrogen, ammonium nitrogen, organic nitrogen, phosphate and potash.

The potassium content of the manure was significantly higher for the control diet compared with the lowest-crude protein diet. The researchers believe this was because the control diet contained more soybean meal, and soybean meal is a rich source of potassium.

Also, ammonium nitrogen was greater at the middle versus the front of the feed trough.

Other than these two observations, manure parameters did not differ significantly by dietary treatment or location along the feed trough. The researchers had expected a significant difference between the experimental diets for ammonia flux and manure nitrogen content because of the significant difference in the crude protein contents of the experimental diets. This result was unexpected and unexplained.

 

Economic analysis

Weekly production data were used to determine weekly egg income, feed cost and egg income minus feed cost per hen housed for each of the three experimental diets (Table 6).

Weekly egg income per hen housed was lowest for the low diet and highest for the control diet. Weekly feed cost per hen housed was also lowest for the low diet and highest for the control diet. Average egg income minus feed cost was higher for both the low and medium diets compared with the control diet.

The weekly farm revenue in this experiment differed among dietary treatments by only fractions of a cent on a per-hen basis. However, when applied to a 1 million-bird flock, weekly feed costs for the low and medium diets would be $8,300 and $7,000 less than for the control diet, respectively. Also, weekly farm revenues for the low diet and medium diet would be $5,900 and $6,800 more than for the control diet, respectively. This would increase annual farm revenue by $306,800 for the low crude protein diet and $353,600 for the medium crude protein diet compared with the control diet.

Burley et al. pointed out that all three of the diets contained more crude protein and more of the essential amino acids than the minimum requirements recommended by the National Research Council (1994) and current recommendations for the breed. However, given the premise that the control diet is typical of commercial laying hen diets, then reducing the crude protein level and formulating to ideal amino acid levels would increase flock returns.

 

The Bottom Line

This research shows an economic benefit from reducing the crude protein restriction in commercial laying hen diets and formulating to ideal amino acid levels.

 

Reference

Burley, H.K., P.H. Patterson and M.A. Elliot. 2013. Effect of a reduced crude protein, amino acid-balanced diet on hen performance, production costs and ammonia emissions in a commercial laying hen flock. J. Appl. Poult. Res. 22:217-228.

 

1. Range of major ingredients in diets

 

-Control diet-

-Medium diet-

-Low diet-

Ingredient, %

High

Low

High

Low

High

Low

Corn

56.03

41.32

59.35

43.26

58.06

45.30

Soybean meal

26.13

13.09

18.15

8.70

14.83

7.25

Poultry byproduct meal

8.00

1.10

8.00

5.80

8.00

5.75

Dried distillers grains plus solubles

8.00

1.20

8.00

5.00

8.01

5.00

Canola meal

5.00

5.00

4.55

5.00

2.94

Blended fat

2.70

0.15

2.25

2.00

Bakery byproduct meal

6.00

6.20

6.00

Wheat middlings

5.32

6.00

6.00

 

2. Analyzed nutrient concentrations for feed samples, %*

Diet

Dry matter

Crude protein

Lysine

Methionine

TSAA

Threonine

Control diet

90.57

21.88a

1.06

0.44

0.85

0.83a

Medium diet

90.49

20.35b

1.04

0.43

0.83

0.76b

Low diet

90.39

19.90b

1.05

0.45

0.84

0.75b

Location

 

 

 

 

 

 

Front of feed trough

90.36b

20.71

1.05ab

0.44

0.84

0.78

Middle of feed trough

90.47ab

20.43

1.03b

0.43

0.83

0.77

End of feed trough

90.61a

20.99

1.07a

0.45

0.85

0.79

a,bMeans in same column and factor with no common superscript differ significantly (P < 0.05).

*Mean of 48 samples.

 

3. Sieving fractions for feed trough samples, %*

 

-Sieve number-

6

8

12

16

20

30

40

50

70

Pan

Diet

Control diet

4.69b

7.74b

9.30b

11.43a

12.60a

14.21

14.10a

8.93

8.85

8.14b

Medium diet

5.67ab

9.60a

10.20a

11.11ab

11.54b

14.56

12.21b

8.73

7.61

8.76ab

Low diet

6.39a

10.32a

10.17a

10.63b

10.90b

13.51

12.71b

8.66

7.56

9.12b

Location

Front of trough

5.48

9.34

10.18

11.33

11.84

14.55

12.32

8.72

7.99

8.23

Middle of trough

6.23

9.84

9.97

10.93

11.40

13.42

13.20

8.57

7.57

8.87

End of trough

5.05

8.48

9.52

10.91

11.81

14.32

13.49

9.03

8.46

8.98

a,bMeans in the same column and factor with a common superscript are not significantly different (P < 0.05).

*Mean of 48 samples.

 

4. Performance results by diet and feed trough location

 

Body-

Egg

Albumen

Haugh

Yolk

Shell

Shell

weight, kg

weight, g1

height, mm

units2

color3

strengh4

thickness, mm

No. of samples

48

30

30

30

30

24

24

Diet

Control diet

1.58

60.49

8.95

93.57

7.73

4,285

0.36

Medium diet

1.58

60.43

9.06

94.15

7.85

4,322

0.37

Low diet

1.55

60.03

8.98

94.07

7.81

4,370

0.37

Location

Front of trough

1.57

60.53

8.86b

93.02b

7.81

4,318

0.37

Middle of trough

1.55

59.89

9.15a

94.94a

7.77

4,394

0.37

End of trough

1.58

60.54

8.99ab

93.85ab

7.81

4,268

0.36

a,bMeans in the same column and factor with a common superscript are not significantly different (P < 0.05).

1Measured during February, April, May, July and September.

2Measured during March, April, June and August.

3Roche color fan.

4Grams of force at failure.

 

5. Egg production results, mean for the experiment

 

Low diet

Medium diet

Control diet

Water, liters/100 birds/day

16.45

16.54

16.73

Feed, kg/100 birds/day

9.94

9.95

10.09

Kg of feed/kg of egg mass

1.92

1.91

1.92

Kg of feed/doz. eggs

1.33

1.34

1.36

Peak hen-day production, %

96.94

96.68

96.68

Weekly egg case weight, kg

20.92

21.09

21.35

Egg mass, g/hen/day

56.13

56.28

56.84

Large Grade A, %

51.58

49.86

45.14

Extra-large, %

22.55

25.77

31.93

Jumbo, %

2.03

2.31

3.48

 

6. Mean weekly economic results, $/week/hen housed

 

Egg

Feed

Egg income

income

cost

- feed cost

Low diet

0.4748

0.2064

0.2684

Medium diet

0.4770

0.2077

0.2693

Control diet

0.4772

0.2147

0.2625

 

Volume:85 Issue:26

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