Phenotypic Correlations Between External Egg Quality Traits in Native Ducks and Geese

Abstract The aim of this research was to evaluate the phenotypic correlations between external egg quality traits in native duck and goose populations reared in Bosnia and Herzegovina. In the native ducks considered, the average egg weight, shape index, shell weight, shell ratio, and shell thickness were 75.21 g, 70.84%, 6.47 g, 8.61%, and 0.34 mm, respectively. In the native geese considered, these traits averaged 163.31 g, 64.34%, 18.21 g, 11.20%, and 0.58 mm, respectively. The correlation analysis revealed that the egg weight was significantly and positively associated with the geometric mean diameter and shell weight in both species (p < 0.05), whereas its correlations with the shape index and sphericity were non-significant (p > 0.05). Moreover, the shape index was significantly and positively correlated with the sphericity (p < 0.05), while both traits exhibited non-significant and negative correlations with the shell weight, shell ratio, and shell thickness (p > 0.05). The shell thickness was significantly and positively correlated with the shell weight and shell ratio in both species (p < 0.05), but largely independent of geometric traits, except in the ducks, where a positive association with the geometric mean diameter was observed. The shell density showed no significant correlation with the egg weight in either species (p < 0.05), whereas the egg weight was significantly positively correlated with the shell weight per unit surface area in the ducks (p < 0.05). These results indicate that geometric traits primarily determine egg weight, while shell quality traits are partially independent of egg size. The findings provide valuable data on the external egg quality traits and their interrelationships in the native ducks and geese considered, offering useful insights for the selection and improvement of their productive traits, particularly within small-scale and extensive poultry systems.