Response of Growing Leghorn Pullets to Long or Increasing Photoperiods

In Experiment 1, Leghorn pullets were reared on either 1) constant 8-hr photo-period to 16 weeks, 2) 8 hr to 10 weeks followed by .5 hr/week to 16 weeks, or 3) 8 hr to 12 weeks followed by 1 hr/week to 16 weeks. At 16 weeks, randomly selected birds were moved to laying cages and all exposed to 14-hr photoperiods. In a second trial, 10 replicate groups of 10 Leghorn pullets were reared to 19 weeks on constant photoperiods of either 8 or 14 hr/day. In Experiment 1, increasing photoperiod had no effect on body weight or carcass composition (P>.05). There was also no effect on early egg production, although early light stimulation resulted in fewer eggs to 52 weeks of age (P<.01). In the second trial, birds reared on 14 vs. 8 hr continuous light consumed more feed (P<.01) and were heavier (P<.01) from 2 to 19 weeks of age. These effects are discussed in relation to rearing programs aimed at inducing early sexual maturity.