480 hatching eggs were obtained from commercial, Ross 308 breeder at 33 and 53 weeks of age, 240 eggs for each breed age. Eggs individually weighed before and after incubation and incubated following usual hatchery practices. Individual embryo weight was recorded at 19d of incubation, relative embryo weight was calculated. A sample of embryo and residual yolk sac was used for measurement of chemical composition in the yolk and albumen base on method of AOAC, 1990. A completely randomized design was used. Eggs weight from Old group was heavier (P0.05) between Y and O group in embryo dry matter, ash, fat, crude protein and nitrogen free extract content, although embryo fat content were increased numerically. There was significant differences (P0.05) between Y and O group in heart weight. Our result revealed that as breeder age advanced, embryo weight, length increased, and embryo from old group had more residual yolk sac and this may cause more malabsorbtion of yolk sac during incubation.
