The purposes of this study were to determine the effects of oviposition time on egg quality and to examine the possibility of estimating egg shell weight using a formula. The interactions in some egg quality measurements were also studied.

During the experiment. 80 white and 64 brown layers were housed in cages and fed with a standard layer ration. The birds were given 17 hours of light per day throughout the experiment. Egg quality was checked four times with two week intervals. At each check, eggs were collected at 09.(oo), 12.(oo) and 15.(oo), on consecutive days. Egg weight (EW), egg specific gravity (ESG) and shell weight (SW) were measured, and then shell ration (SR) and shell weight per unit surface area (SWUSA) were calculated. In addition, the SW was estimated by two formulae using EW and ESG. The data from white and brown layers were analysed separately. The effects of oviposition time and age of hens were tested with variance analysis. The correlation coefficients between quality measurements were determined.

The effect of age was not significant (p>0.05). Collection time had a significant (p<0.05) effect on the EW of white and brown layers. For the two groups, the heaviest EWs were determined at the first collection time, and the lightest EWs at the last time. Although the measured SW was not affected by the collection time, it was highest at the first collection.

Significant correlations were detected between measured and calculated SW (r between .6612 and .8521, p<0.01 overall). The ESG was more closely correlated with SR and SWUSA than with SW. In addition, negative correlations were found between EW and ESG as well as with SR.