The hen's egg: Relationships of seven characteristics of the strain of hen to the incidence of cracks and other shell defects

Multiple regression and path‐coefficient analysis show that the factors with greatest influence on the incidence of cracks and other shell defects in three random‐sample tests of 47 entries of 28 strains were, in descending order, mean shell colour, mean shell thickness, mean egg production and mean egg weight, and that median age at maturity, mean body weight at 140 d and mean weight increase between 140 and 500 d had no effect. 2. Breeders who wish to exercise indirect selection for low crack incidence should consider selecting for dark shell colour rather than high shell thickness.