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Selection for egg shell strength in laying hens using shell membrane characteristics
K Johansson1, J Orberg, A B Carlgren
1Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden.
British Poultry Science
|September 1, 1996
Summary
Selecting for stronger eggshell membrane attachment in laying hens significantly improved attachment strength but resulted in thinner shells. This indicates a trade-off when breeding for enhanced eggshell integrity.
Area of Science:
- Animal Science
- Genetics
- Poultry Science
Background:
- Eggshell strength is crucial for preventing breakage during handling and incubation.
- Improving eggshell quality is a key objective in poultry breeding programs.
- Attachment strength between the shell membrane and calcium shell influences overall eggshell integrity.
Purpose of the Study:
- To investigate the potential of improving eggshell strength in White Leghorn laying hens.
- To assess the direct and correlated responses to divergent selection for shell membrane-calcium shell attachment strength.
- To estimate genetic parameters for attachment strength and eggshell thickness.
Main Methods:
- Divergent selection was applied to a White Leghorn strain for attachment strength.
- Multivariate analysis was used to estimate genetic parameters.
- Measurements included shell membrane characteristics and shell thickness.
Main Results:
- Significant direct selection response achieved for increased attachment strength.
- Favorable correlated response observed in reduced frequency of cracked eggs.
- Selection for stronger attachment led to thinner eggshells; weaker attachment resulted in thicker shells.
- Heritability estimates for traits were high (0.30–0.70).
Conclusions:
- Breeding for increased attachment strength can improve eggshell integrity but may negatively impact shell thickness.
- An unfavorable genetic correlation between attachment strength and shell thickness likely contributed to observed responses.
- Increased mortality during incubation and hatching suggests natural selection against significant changes in attachment strength.