Date of Hatch and Day Length Affect Age at First Egg

INTRODUCTION DURING the course of an unpublished study to evaluate environmental factors affecting rate of egg production, it was deduced that age at first egg among genetically similar pullets should be closely related to daily hours of illumination. As a corollary, winter hatched pullets should mature earlier than spring hatched pullets. Evaluation of these relationships may enable poultry breeders to correct their genetic selection for early maturity in accordance with date of hatch or persuade them to limit comparisons to groups of pullets hatched during a very limited period. Selection is effective in proportion to the degree with which it reflects genetic variation rather than variation due to environment. Several studies of the effect of date of hatch on age at first eggs are summarized by Lippincott and Card (1939) and Jull (1940). Conclusions as to the effect of date of hatch on age at first egg drawn from these . . .