Effect of breed and age of hens on the yolk to albumen ratio in two different genetic stocks.

A commercial egg-type chicken (ISA Brown; CEC) and a dual-purpose pure breed of the Korean Native Chicken (KNC) were compared for yolk to albumen (Y:A) ratio and their major egg characteristics at seven different ages. The eggs from KNC were significantly (P < 0.01) lighter in egg, albumen, and shell weight than those from CEC. However, the yolk weight and Y:A ratio of the eggs from KNC were significantly (P < 0.01) heavier or larger than the ones of CEC. The effect of age on the yolk, shell weight, and shell thickness was highly significant (P < 0.01), whereas significant differences were not found for Y:A ratio and other major egg components. The breed-by-age-of-hen interactions were significant for shell weight (P < 0.03) and shell thickness (P < 0.01). The yolk, albumen, and shell weight were positively (P < 0.001) associated with egg weight in both breeds. The association of Y:A ratio with egg weight in both breeds also were highly significant (P < 0.001) but negative. The results of the present study indicated that the different effects on the Y:A ratio were due to breed rather than age. Results suggest that the eggs from KNC are more desirable for use in products made of yolk than for consumption as table eggs.