COOPERATIVE EXTENSION 

UNIVERSITY OF CALIFORNIA 

CALIFORNIA POULTRY LETTER

January 1999

In This Issue:

• Intentional Delay of Sexual Maturity in White Leghorn Laying Flocks
• Poultry Health Symposium is Scheduled for March 9th
• Age of Eggs at Retail

Intentional Delay of Sexual Maturity in White Leghorn Laying Flocks

Recent reports of experiments with intentional delay of sexual maturity have concentrated on the egg size improvement issue. Several controlled experiments have been run with publication of results in scientific journals. Performance can be affected - definitely on a short-term basis and in some cases results may still differ at the end of the laying cycle. Complete cycle advantages for this practice - at least in the US, are questionable.

Most analyses of the question "What is the best age for stimulating flocks into production?" show higher profitability for flocks which commence laying at earlier ages. Even though early egg weight may show slight depressions, overall performance favors the early attainment of egg production. (See May 1998 California Poultry Letter).

Today, breeders usually answer this question in one of two ways: 1). If a given weight (2.8 to 3.1 pounds) is reached, stimulation can be started as early as 15 weeks of age, or 2). Wait until at least 19 weeks and then only if they are at or above recommended body weight.

In a 1991 UC experiment, two strains of White Leghorns were placed in the lay house at 18 weeks of age and fed the same pullet diet. At 20 weeks of age, one-half of each group was placed on a full-fed layer diet while the other half had their feed removed for five days. This is a program commonly practiced in Brazil and Japan for improving egg size at the start of the laying period. Our test ran for 40 weeks of lay.

The most obvious result was a reduction in body weight for the first two weeks. The feed restricted birds lost 15.7% of their 20 week weights during the first 5 days, while their full- fed sisters gained 5.7%. At 22 weeks the restricted birds weighed 3.04 pounds compared to 3.24 pounds for the full-fed group. By 24 weeks, weights were comparable and remained this way until the end of the test at 60 weeks. Overall results for the 40 week test are listed in Table 1.

Table 1. Summary of results - two strains combined - 21 through 60 weeks

Egg production rates favored the full- fed birds through 25 weeks of age (5 weeks), but was comparable through the end of the test.

Eggs were weighed every four weeks beginning at 24 weeks and no significant differences were observed during any of the 19 comparisons. Weights were always within one gram/egg between the two treatments and results shifted back and forth.

There are situations, though, where egg production is simply not advantageous at a point in time. For example, in May-July of 1998, egg prices for large eggs averaged only 45 cents/dozen while prices for medium eggs averaged only 27 cents per dozen in Southern California. Under such conditions, a delay in production may be justified if it didn't?t affect total egg numbers.

In the UC experiment, the same price for eggs was used throughout the experiment. A variable price, as in the real world, might have shifted results to favor one system or the other. Regardless, very little effect on performance was observed.

A copy of the data generated during this experiment is available from the author.

Don Bell

Poultry Health Symposium is Scheduled for March 9th

The Third annual Poultry Health Symposium will be held at the new Stanislaus Country Cooperative Extension facility in Modesto on March 9th for California poultry producers from 9 am to 3 p.m. Our keynote speaker, Dr. Craig Riddell from Saskatchewan, Canada will discuss the emerging production and disease problems related to ?J virus? infection of chickens. This disease has recently been recognized throughout the US, including California, as a cause of tumors and immune depression in both broiler and layer chickens.

Other speakers will inform us of new developments in understanding the impact of Bordetella avium and Ornithobacterium rhinotrachealis (ORT) infections in chickens; provide an update on mycoplasmosis (MG); examine the ramifications of Salmonella enteritidis and review other timely issues.

This symposium will be hosted by the UC Cooperative Extension and California Veterinary Diagnostic Laboratory System. Dr. Joan Jeffrey, UC Extension Poultry Veterinarian will be coordinating the program.

Morning refreshments and lunch will be provided. The fee for the program is $20. A detailed program and registration form will be mailed to participants of last year?s symposium and is available from Dr. Jeffrey?s office (telephone: (209) 688-1731. We look forward to your participation.

Joan Jeffrey

Age of Eggs at Retail

In a 1996 study of egg quality in 115 supermarkets in six states, it was observed that the average age of eggs in the retail display case was:

• 11.7 days for white eggs
• 14.8 days for brown eggs
• 16.7 days for specialty eggs

It was also noted that 19% of the 771 dozen eggs sampled were over three weeks old (from the pack date). Only 21% were 7 days or less.

How do eggs get this old in what should be a relatively simple process of moving eggs from the farm to the consumer? The typical process should be accomplished in 7 days or less.

Table 1. Estimated egg storage time

Eggs are handled in a wide variety of ways, but it's apparent that the process of getting the egg from the farm to the consumer is subject to considerable delay in too many cases. Ideally, an egg order for a specific store should be received at the packing plant (possibly through the headquarters of the retailing firm), filled and transported the the individual store or the firm's warehouse for transshipment within just a few days of the order. Storage in the back room of the retail store should be 3 days or less assuming 3 day a week deliveries. Thus, the total elapsed time should all be within a seven day period.

Where do eggs "reside" that have been around for 20 days or more days? If this happens to your eggs, you had better do some detective work to get the age factor back to 7 days or less or you'll hear about it from your customers.

Interior Egg Quality - Have We Forgotten About It?

A delay in the marketing of eggs can have two major effects - a loss of weight and a loss of interior quality. Table 2 demonstrates the loss in weight of cartoned eggs over time when stored at 45 degrees.

Table 2. Loss in egg weight over time

These figures may not appear to be excessive, but they could represent losses sufficient to downsize a dozen eggs into a smaller classification. A single large egg must weight at least 54.3 grams.

In the 1996 national study, interior quality (as measured by Haugh Units) averaged:

• White eggs - 69 Haugh Units
• Brown eggs - 64 Haugh Units
• Specialty eggs - 66 Haugh Units

Individual states ranged from 63 to 76 Haugh Units for white eggs and 60 to 70 Haugh Units for specialty eggs. Usda quality requirements are 72+ Haugh Units for AA eggs and 60 Haugh Units for A eggs.

Interior quality averaging less that 65 Haugh Units was seen in 45% of the cartons sampled. in addition, 4.6% of all cartons had 50"% of the eggs with 55 or less Haugh Units. This would place these eggs in the "B" category of quality.

Would oiling help to maintain a higher interior egg quality level?

Don't most egg packaging plants already oil? There is no documented evidence to state that eggs are not oiled or not oiled as much as they used to be. Anecdotal comments from industry observers, though, would lead us to believe that oiling is not as common as it once was and this could be a major contributor to the "poor" interior quality observed in our national survey.

Research demonstrating oils ability to maintain albumen quality was conducted extensively in the 1950's, '60's and '70's. Very little has been done in recent years because of the widespread acceptance of the practice. In light of the retail study, it might be appropriate to revisit a set of typical results.

Improvement in interior egg quality can be accomplished by either shortening the interval between lay and sale to the consumer (under refrigeration) or by applying time-tested technology to preserve the quality that is already there. The industry can't assume the consumer is satisfied with the quality of eggs they receive. The chef knows the difference between old eggs and fresh ones, and can readily see the differences between eggs with 60, 70, or 80 Haugh Units.

Don Bell, January Editor

Ralph Ernst, Technical Editor