Egg Size as Influenced by Morning or Evening Lights

Leghorn-type hens (40 weeks of age) were used to study the effect of: 1) increasing the morning photoperiod and total photoperiod, and 2) shifting artificial lights from morning to evening while maintaining a constant photoperiod length. Time of lay, egg size, egg production, and feed consumption were evaluated. By increasing morning photoperiod, egg weights were inreased during the first 4 weeks. After the 3rd week, ambient temperature decreased, and egg weights gradually equalized for the two treatment groups. Number of eggs laid before 1000 hr by birds exposed to morning light was increased, which indicated a shift in time of oviposition. Egg production for the birds with increased morning light was 4% higher for the first 4 weeks and 1% higher for the second 4 weeks than control birds. Birds subjected to increased morning light consumed 2.5 g more feed/bird/day than the control birds for the first 5 weeks, after which time feed intake was equal. When artificial morning lights were shifted from morning to evening, egg weights were reduced, and the laying cycle shifted toward the afternoon. Egg production and feed consumption were not significantly affected by evening light treatment.