Management
P-88 March, 1966
Poultry for Profit
Cooperative Extension Service PURDUE UNIVERSITY Lafayette, Indiana
LIFE SCIENCE LIBRARY
APR 25 1966
PURDUE UNIVERSITY
Why Egg Size Varies
by Joe W. Sicer, Animal Sciences Department
It is not unusual for medium size eggs to be cut 5 cents to 10 cents a dozen below the price for large eggs. If you are getting too high a proportion of medium or smaller eggs, your average egg price will suffer even though your egg quality grade may be very high.
Unfortunately, there is usually not much hat a poultryman can do to improve the situation quickly. An understanding of the various factors that influence egg size may be of much help in the future.
Here are the most important factors that affect egg size:
Breeding
Egg size is an inherited trait. Environmental factors may result in smaller eggs but the upper limits in egg size are pretty well determined when the pullet is hatched.
High egg production and smaller egg size tend naturally to be linked together.
The breeder has therefore had a real job to maintain an egg size that satisfies market demand and at the same time turn out birds with an ever increasing ability to lay more eggs. This has been done.
The Random Sample Egg Laying Tests show that there is close correlation between
egg size and the strain of bird. A report on these tests, ("Egg Production Tests -- United States and Canada"), is issued each year by the Agricultural Research Service, U.S.D.A., Washington 25, D. C. Study the report and you can see the egg size to expect from various strains . An average egg weight of 24 ounces per dozen for the year will yield only about 60% of eggs grading large or better.
For more than 70% of all eggs to grade large or better you will need a strain with an average egg weight of 25 ounces per dozen.
Age of Bird
When pullets start to lay, 80% or more of their eggs will be under 21 ounces per dozen. Pullets are doing well if when they are 8 months of age 50 percent or more of their eggs will grade 24 ounces per dozen or larger. In another 2 months, 75 to 80 percent should be that large. Egg size should continue a gradual increase until the birds are around 12 to 14 months of age after which some decrease in egg size may be expected.
Other factors, such as the weather and date of hatch may cause a substantial variation in this trend of egg size with age.
There is also a tendency for egg size to drop slightly from the first to the last egg in the clutch.