Selection has been conducted in White Leghorn population for increased (weak line) or decreased (strong line) non-destructive deformation. The same environment conditions were given to the both lines through the all generations. In generation 10, non-destructive deformation was reduced to 51.9 micro m/kg in strong line and increased to 100.6 micro m/kg in weak line. Breaking strength in generation 10 was 3.75 kg in the strong line and 2.17 kg in the weak line. Selection for non-destructive deformation was effective in improving egg shell strength and the strong and weak lines were separated genetically. The degree of selection response was not equal in the two directions. Non-destructive deformation had a heritability value of 0.33 and genetic correlations were -0.77, -0.89 and -0.94 with breaking strength, shell thickness and percentage shell in the weak line, respectively. Genetic correlations of shell traits with rate of lay were negative but with egg weight were positive. The selection for the strong shell can increase the egg weight but reduce the rate of lay.

K. Nirasawa, Y. Nagamine, H. Takahashi, H. Takeda, T. Furukawa, T. Takeda

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 24: Sheep and goats (fibre); sheep and goats (meat and milk); poultry; horses; buffaloes., , 345–348, 1998
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