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Age changes in genetic and environmental variation in laying hens
L E Liljedahl1, J S Gavora, R W Fairfull
1Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Summary
As laying hens age, both genetic and environmental variations in egg production increase. This suggests aging impacts birds' ability to handle environmental factors and activates new genes to counteract aging effects.
Area of Science:
- Animal Genetics
- Poultry Science
- Quantitative Genetics
Background:
- Egg production traits in laying hens are influenced by genetic and environmental factors.
- Understanding how these factors change with age is crucial for optimizing poultry breeding and management.
- Previous studies have explored age-related effects, but comprehensive analysis across different populations is needed.
Purpose of the Study:
- To investigate the effects of aging on genetic and environmental variation in egg production, egg weight, and egg quality in laying hens.
- To estimate variance components (sire, dam, residual) related to these traits in different chicken populations.
- To explore the biological mechanisms underlying age-related changes in variation.
Main Methods:
- Analysis of data from a crossbred population in Sweden to estimate sire and residual variance components.
- Estimation of sire, dam, and residual variance components using data from eight generations of Canadian chicken strains (two control, four selected for high egg production).
- Statistical modeling to partition genetic and environmental sources of variation.
Main Results:
- Results indicated an increase in both genetic and environmental variation for egg production traits with advancing age.
- A clear-cut separation of all genetic and environmental variance components was not achieved.
- The study suggests aging impairs the birds' ability to cope with environmental conditions, increasing environmental variation.
Conclusions:
- The observed increase in environmental variation with age is likely due to impaired physiological resilience.
- The simultaneous increase in genetic variation may result from the activation of new genes to counteract aging.
- Alternatively, reduced DNA transcription accuracy in older birds could increase genetic "error variation" and environmental variation.
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