COOPERATIVE EXTENSION

UNIVERSITY OF CALIFORNIA

CALIFORNIA POULTRY LETTER

May 1998

In This Issue:

  • Comparing White and Brown Egg Layer Performance.
  • Comparing White and Brown Egg Layer Performance - Interior and Exterior Egg Characteristics and Composition.
  • Egg Shell Quality - Its Impact on Production, Processing and Marketing Economics.
  • Stimulation of Early Production in Young Pullet Flocks

Comparing White And Brown Egg Layer Performance The North Carolina Layer

Table 1 lists the results for the two tests (combined) during the 1992 to 1995 period. Each test included 8 or 9 strains of white egg producing chickens and 4 strains of brown egg birds.

Each test was conducted with different housing types and at different cage densities over two cycles of production. Results are shown for each type of bird and for each cycle of production.

Egg Production

Interestingly, in the combined tests, the brown egg layers out-performed the white egg layers in the first egg production cycle by 4 eggs per hen-housed, but dropped behind in the second cycle by 13 eggs.

Mortality

A similar pattern for mortality was observed- reduced mortality during the first cycle, but a higher rate in the brown egg birds in the second cycle.

Table 1. Comparison of White and Brown Egg Layer Performance*

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Trait                     Cycle 1(44 wks)              Cycle 2(39 wks)
---------------------   --------------------         --------------------
                         White       Brown           White       Brown
-------------------------------------------------------------------------
Eggs/Hen-housed          233.5       237.5           163.5       150.5
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Mortality/week (%)          .20         .19             .21         .31
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Feed/day (lbs/100 hens)     .254        .269            .259        .279
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Av. Egg Weight (grams)    61.0        63.6            66.9        69.9
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   X-lg + (%)             39.6        55.3            80.0        88.9
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   Large (%)              41.4        33.1            18.0         9.9
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   Med, small, pw (%)     19.1        11.6             2.0         1.3
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Cracked eggs (%)           2.0         2.1             2.5         2.2
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Loss eggs (%)               .2          .2              .5          .4
-------------------------------------------------------------------------
* North Carolina - 1992 to 1995 Tests

Feed Consumption

The brown egg layers consumed 6.8% more feed during the two cycles compared to the white egg layers. This was equivalent to 1.5 to 2.0 pounds of feed per 100 hens per day.

Egg Weight and Sizes

As expected, egg weight was significantly more in the brown egg birds and during the second cycle for both breeds. The net increase in weight averaged 4.4% for the brown egg birds over the white egg birds.

The proportion of x-large and jumbo eggs was much higher in the brown egg breeds and during the second cycle. During the second cycle of production, the brown breeds produced almost 89% x-large and jumbo eggs.

Cracked and Loss Eggs

Egg breakage was slightly higher in the second cycle compared to the first (2.8 vs 2.3%), but the breeds were quite comparable.

Don Bell
Extension Poultry Specialist

Comparing White And Brown Egg Layer Performance - Interior And Exterior Egg Characteristics And Composition

Researchers at Texas A&M University, in 1985, published a series of papers which compared three strains of white egg birds with three strains of brown egg birds. Emphasis of the research was on the egg itself -- flock performance other than egg quality and composition were not shown.

Even though this data is now some 15 years old, we thought the comparisons would be of interest. More current published information with U.S. strains and breeds does not seem to be available.

Table 2 summarizes the data from these three papers comparing white and brown egg quality characteristics over a 48 week-long production cycle. Molting was not practiced.

Table 2. Comparison of White and Brown Egg Quality Characteristics *

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Trait                          White eggs         Brown eggs
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Shell thickness (inches)          .01535 **          .01449
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Shell as a % of egg wt.          9.4**              8.7
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Albumen as a % of egg wt.       63.1**             64.5
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Yolk as a % of egg wt.          27.6**             26.8
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Albumen solids (%)              10.8**             11.2
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Yolk solids (%)                 52.7               52.7
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Haugh units                     81.9               85.1**
-----------------------------------------------------------------
* Texas A &M University, 1985,
** = statistically different (P<.05) 

Shell Thickness

Results of this study indicate thicker shells and a higher percent of shell as a proportion of total egg weight in the white shelled eggs. The shell thickness measurements for the white eggs were almost 6% more than for the brown eggs. Similarly, shell weight as a percent of egg weight was 8% more for the white eggs. Absolute shell weight favored white eggs by 6% (5.6 grams vs 5.3 grams) even though the brown eggs were 1.3 grams per egg heavier.

Many individuals incorrectly assume that the shells from brown shelled eggs are stronger than those produced by white shell breeds. The North Carolina reserch tends to dispute this assumption in terms of candled egg breakage and the shell thickness data from the Texas study certainly shows thicker shells in the white egg strains.

Composition of Eggs

The significantly smaller percentage of shell for brown eggs, is associated with a lower yolk percent and a significantly higher albumen percent. As a result of higher albumen content, Haugh units measurements were 3.2 units higher in the brown shelled eggs.

Don Bell
Extension Poultry Specialist

Egg Shell Quality - Its Impact on Production, Processing And Marketing Economics

The economic losses from egg breakage are dependent upon the amount and severity of breakage and upon the prices for good, cracked and loss eggs. If we assume that good eggs are valued at $.55/ dozen, cracked eggs at $.20/dozen and loss eggs at zero value, this would translate to a loss of .3 cents/dozen of $.08/hen/year for each 1% of egg breakage. For loss eggs (no income), 1% would be equivalent to .5 cents/dozen or $.11/hen/year.

Placing Egg Breakage Losses in Perspective

An $.08 cents/hen/year loss in income may not sound to be of economic significance, but when compared to a conservative estimate of annual profits for the egg industry, it becomes very significant.

If we assume that annual profits per hen are $1.00, a 1% increase in egg breakage would represent an 8% loss in profits; a 1% increase in losses would represent an 11% reduction in profits. These are certainly not insignificant effects. When all the factors affecting egg breakage are put together, the issue becomes a major concern for all producers. Control of the problem can be the difference between a successful operation and one that could easily go bankrupt.

Cost to the US Industry

The emphasis in the above discussion is on the effects to the individual company. The company is the one that can remedy the problem and is the one that suffers if it is not remedied. The effect on the industry as a whole is of interest only because of its magnitude compared to other issues of importance to the industry.

Table 3 summarizes the cost of egg breakage to the US egg industry from production through egg grading. This does not include the breakage that remains in the consumer's carton which is estimated to be 5% of the number of eggs sold.

Table 3. Summary of Economic Losses to the US Egg Industry Due to Egg Breakage From Production Through Egg Grading.

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Source of            % Cracks        Losses/Hen     Total Industry
Breakage             or Loss             ($)           Losses ($)*
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Sound shell          3.9 % (loss)       0.48         120.0 million
through cage
bottom
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From cage through    5.0 % (cracks)     0.40         100.0 million
grading              1.0 % (loss)       0.11          27.5 million
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Total                4.9 % loss +       0.99         247.5 million
                     5.0 % cracks    
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* Uncollectible eggs and eggs cracked after grading are not considered economic losses.

It is suggested that the direct costs (losses) are $247.5 million per year. This is essentially $1.00 per average hen. A high percentage of these cracks can be corrected with changes in management procedures!

In addition, there are associated costs from the candling and the purchase of equipment to detect breakage, labor and packaging costs for rehandling rejected eggs, customer dissatisfaction with our industry's products, clean up costs, and possible human health risks associated with eating mishandled cracked eggs.

A copy of the complete report on this subject is available from the author.

Don Bell
Extension Poultry Specialist

Stimulation of Early Production in Young Pullet Flocks

Breeders have successfully improved their stocks at the rate of at least 2.5 eggs per year for the last 10-15 years. This has been achieved by selection for earlier maturity, higher performance peaks and more persistent egg production at later ages. Age at 50% egg production has moved earlier by more than six and thirteen days for white and brown egg layers respectively during the 1980's.

U.S. egg producers now commonly stimulate pullets into production at 16 to 18 weeks of age compared to 20 weeks just a few years ago. With genetic selection pressure for early egg size, this early stimulation is definitely justified.

Traditionally, the age at sexual maturity is described as the age at first egg, or the age at a specific rate of lay (5-10%). Such measurements are not commonly available in the commercial egg industry and therefore we have chosen to describe sexual maturity as the rate of lay during the 22nd week of age.

Table 4 summarizes various performance traits associated with sexual maturity.

The data in table 4 has been calculated by linear regression analysis which associates performance (Y axis) with the rate of lay at 22 weeks (X axis).

Table 4. The Relationship of Various Performance Traits To Rate of Lay at 22 Weeks.*

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                                     Rate of lay at 22 weeks of age (%)
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Trait                 20       30       40       50       60       P**
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HD egg prod. rate    92.2     92.2     92.3     92.3     92.4      ns
at peak (%)
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HD egg prod. rate    78.5     79.3     80.1     80.9     81.6      .001
(20-60 wks) (%)
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HD egg production    77.3     77.1     77.0     76.8     76.7      ns
rate @ 60 wks (%)
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HD egg production     .45      .46      .46      .47      .47      ns
slope (30-60 wks)
(% decrease/wk)
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Eggs/Hen-housed     219.0     221.1    223.2    225.3    227.4     ns
to 60 wks
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Egg weight @ 30      45.5      45.6     45.6     45.6     45.7     ns
wks (lbs/case)
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Egg weight 20-60     47.5      47.6     47.6     47.4     47.7     ns
wks (lbs/case)
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Total egg mass       13.00     13.11    13.23    13.35    13.47    .001
(kg/hen-housed
to 60 wks)
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Egg Income minus     $5.09     $5.15    $5.20    $5.26    $5.32    .001
feed cost/hen-
housed to 60 wks
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* 203 National flocks, calculated linear regressions.
**  P= probability level,  ns = not statistically different (P<. 05). 
Hen-housed egg production is seen to increase about 2 eggs with each 10% higher rate in the 22nd week. Total egg mass per hen housed also increases by .11 kg (about 1/4 pound). As can be seen, each increment of earlier sexual maturity is associated with 5-6 cents additional egg income minus feed costs. Interestingly, no egg size effects were observed.

Don Bell
Extension Poultry Specialist


Don Bell, May Editor
(909) 787-4555
E-mail: don.bell@ucr.edu

Ralph Ernst, Technical Editor
(530) 752-3513
E-mail: raernst@ucdavis.edu