Variation in egg content density makes egg specific gravity a poor indicator of shell weight

A study was conducted to measure the variability in egg content specific gr avity (ECSG) among breeds and strains, and ages of laying hens. Also inform ation is presented concerning how the specific gravity of egg content (EC) affects the specific gravity of egg (ESG). The observed ECSG ranged from a Low of 1.0298 to a high of 1.0352. Based on the formula of Harms ef. al. (1 990) a change of ECSG from 1. 029 to 1. 035 would change the ESC from 1.082 3 to 1.0883 and the eggshell weight from 5. 64 to 6.18 g. ECSG on a commerc ial farm ranged from 1.0323 to 1.0352. This resulted in calculated ESG from 1. 0856 to 1. 0885 and calculated SW from 5. 84 to 6.21g. Researchers and industrymen must be very careful in using ESG data in making decisions rela ting to eggshell quality.