EMBRYONIC WEIGHT AS A SELECTION CRITERION IN ALTERATION OF GROWTH CURVES OF DOMESTIC BIRDS — DATA FROM THE DOMESTIC TURKEY

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Abstract
The effect of egg weight on the relationship of embryonic weight to postembryonic weight has been studied in four lines of the domestic turkey. A line previously selected for large size at 12 weeks had heavier embryos at 18 days of incubation than a line previously selected for large size at 24 weeks though this difference was not satistically significant. The correlation of egg weight with embryo weight increased from low insignificant values at 12 days of incubation, remained high at hatching and declined after hatching. The rate of increase and decline varied with the line. Significant differences between sire families were detected after 18 days of incubation in all lines. Sire average correlations of 18-day embryo weight with poult weight yielded inconsistent results in that significant correlations were obtained for 1 line in 1 year and another line in another year. This inconsistency is likely due to the small number of sires which could be used. The usefulness of embryonic weight as an aid to altering the postembryonic growth of any species of birds seems real though it will have to be carefully evaluated in each situation.