Statistical determination of chick sex from pre-hatch egg measurements

This study was aimed at using weight and morphometric measures of hatching eggs to predict the sex of chicks they would produce a priori, by building a statistical discriminant function.  The data for the study came from three different strains (Anak, Marshall and Ross) of broiler hens that have adapted well to the hot humid environment of South Western Nigeria.  A total of 1826 hatching eggs of the three strains were incubated, out of which only 1002 were successfully hatched. Eggs for the study were appropriately tagged and hatched in individual hatching compartments to prevent crossing of the chicks at break-out, and were immediately tagged and sexed by anatomical inspection of vent by a professional.  A Principal Component Analysis (PCA) indicated that the first two components accounted for 98% of the total variation, with high loadings from egg weight, length, width and shape index. These variables were used to build a discriminant function in predicting chick sex across the three strains. There were significant (P<0.01) differences in fertility and hatchability across the strains with fertility been highest in Marshall (86.67%) but least in Ross (52.77%) strain, whereas hatchability was highest in the Ross (82.22%) but least in Marshall (72.67%) strain. It was observed that the accuracy of the prediction method was consistently higher in male than female chicks across the three strains studied albeit with different precision across the three strains.   Key words: Morphometric measures, discriminant function, fertility.