Eggshell translucency and its association with hatch success in broiler breeder eggs: Insights from field data

Eggshell quality and broiler breeder flock age are critical to hatchability; however, limited quantitative information exists on their individual and combined effects. This study aimed to characterize the association of eggshell quality and flock age on hatchability. A total of 22,170 eggs were collected from 738 broiler breeder flocks (Ross 708) between 25 and 65 wks. of age, from multiple commercial hatcheries in the U.S. All eggs were individually evaluated for shell lightness, thickness, breaking strength (BS), translucency score percentage (TS1, TS2, and TS3), and total translucency score (TS, the sum of the product of score and percentage). Commercial hatch of fertile (CHOF) of the flock is recorded by the eggs from the flock. Pearson's correlation, partial correlation, linear regression and LASSO regression were conducted in R. Random forest analysis and SHAP value interpretation were conducted in Python. Significance level was set at P < 0.05. Pearson's correlation showed that CHOF is negatively correlated with age, lightness, thickness and TS3 (P < 0.05), while a positive correlation was observed with BS (P < 0.05). Regression analyses revealed quadratic relationships of CHOF, thickness, TS1, TS3, and TS with flock age, whereas BS and TS declined linearly as flocks aged. LASSO regression identified flock age, TS, and TS3 as the most relevant indicators of CHOF. Random forest SHAP analyses similarly indicated that age and lightness are the features with the greatest influence on CHOF. Partial correlations controlling for age showed that CHOF remained significantly associated only with TS (r= -0.35), TS1 (r = 0.28), and TS3 (r= -0.30). Overall, flock age emerged as the predominant factor associated with CHOF. Although thickness and BS showed associations with hatchability, they were largely age-dependent and therefore less reliable as standalone indicators. In contrast, shell lightness and translucency traits were less confounded by age, suggesting they may serve as more robust indicators for predicting CHOF in commercial broiler breeder operations.