Relationship between hatchability and non-destructive physical measurements of chicken eggs

The current study was aimed at exploring the relationship between egg physical parameters that can be evaluated before incubation without egg breakage and hatchability of chick embryos. Eggs from laying hens of the White Leghorn (WL), Rhode Island White (RIW) and Rhode Island Red (RIR) lines were examined using a ranking system for analysing influence of egg parameters on hatchability. Specifically, eggs were subdivided into three groups whose non-destructive measurement values were: (i) within the mean +/- standard deviation (sigma), (ii) < mean minus sigma and (iii) > mean plus sigma. As a result, the smaller WL and RIW eggs, where values of weight, volume, surface area, length and maximum breadth were < mean minus s, appeared to be more successful at hatching than the bigger ones. Hatchability of the more 'round-shaped' WL and RIW eggs, whose shape index was 0.76-0.80, tended to be higher. Effect of egg-specific gravity on hatchability varied in different layer strains, and genetic background seemed to be an essential factor determining relationship between hatchability and other egg characteristics. The RIW eggs of larger weight with a relatively small surface area appeared to have decreased hatchability, supposedly due to insufficient gas exchange of embryos.