Weak correlation between eggshell thickness and breaking strength in Japanese quail suggests a need for separate assessment

Based on experimental evidence obtained in Japanese quail (Coturnix coturnix japonica), concurrent determination of eggshell breaking strength in avian reproduction studies in addition to the routine parameter eggshell thickness is recommended. After transformation of breaking strength data, a regression analysis was performed on a large sample of eggs (n = 815) from untreated hens. A need for concurrent assessment of both endpoints was substantiated by their poor correlation that became apparent by a rather low coefficient of determination (r(2)) of less than 15%. It was further supported by strongly diverging results when sub-sets of eggs from smaller and more homogenous groups of quail in a number of one-generation studies were analysed for correlation of the two parameters.