Genetic Factors Affecting Egg Shell Quality

SummaryTo investigate the inheritance of egg shell quality, it is necessary to develop methods for measuring the attributes of egg shells, and also the relationship between such measurements and the incidence of breakage in the field. Various measurements are available, including shell thickness, specific gravity, and the breaking strength and these have been used to study the genetics of egg shell quality.Most studies have indicated heritability in the medium range. Selection experiments have confirmed these estimates, and considerable progress has been reported from both long term and short term studies. Experiments selecting in opposite directions have been successful in creating lines with widely different shell quality characteristics.Genetic correlations of shell quality traits with other economic characteristics such as egg production and egg size are not thought to be major barriers to progress in both sets of characteristics. More important is the slow-down in progress for the other economic traits, if selection effort is diverted to shell quality. This creates a dilemma for the producers of commercial breeding stock who must strive to improve all traits simultaneously.