The Effect of Season of Maturity of the Laying Hen on Subsequent Egg Size at Periodic Intervals in the Laying Cycle

Seven laying trials, each 400 days duration, were conducted in successive calendar years in a manner that resulted in each trial being initiated two calendar months later each year. At least 2400 laying hens were involved in each trial. Egg size determinations were made daily or weekly for the duration of each trial and other performance criteria were also obtained. Laying hens which reached maturity (24 weeks of age) during the fall or early winter months attained larger egg size earlier in the production cycle and maintained this size advantage throughout the trial year. However, those hens which reached maturity in the spring and early summer months produced a higher percentage of small and medium eggs both initially and for the duration of the production cycle. This higher production of medium and small eggs occurred in the summer months when the greatest price spread between large and medium eggs also occurs. Neither bird size at maturity nor rate of production appeared to be contributing factors to the seasonal difference in egg size.