Significance of growing photoperiod and light stimulation at various ages for Leghorn pullets subjected to regular or ahemeral photoperiods.

Leghorn pullets were cage reared to 15 or 19 wk of age in environmentally controlled rooms that provided either 8 h or 14 h of light per day. In Experiment 1, birds were moved to laying cages at 15 wk of age and subjected to either 14 h light (L): 10 h (D) dark or ahemeral 14L:14D photoperiods. Feed intake, egg weight, shell quality, and egg production were monitored to 67 wk of age. In Experiment 2, pullets were moved at 19 wk of age and subjected to 14L:10D or 17L:7D light programs. Production parameters were measured as previously described. No significant (P greater than 0.5) interactions were observed between rearing and laying photoperiods, suggesting that increase in the length of photoperiod around time of maturity is not essential for adequate performance. In Experiment 1, ahemeral lighting resulting in reduced egg production, whereas egg shell quality and egg weight were improved (P less than .05). In both experiments, the 14-h rearing program resulted in improved egg size together with improved eggshell quality (P less than .05). Whereas increased egg size may relate to body weight, no explanation is apparent for the consistent pattern with respect to shell quality. In Experiment 2, poorer shell quality was observed with 17 vs. 14 h light per day. It is concluded that light stimulation at maturity has little effect on overall egg production. Improved shell quality observed with birds reared under 14 h light vs. those reared under 8 h per day may relate to a less rapid attainment of peak egg production.