Early Application of Conventional or Ahemeral Photoperiods in an Attempt to Improve Egg Size

Treatments were arranged as a 2 × 2 × 3 × 2 factorial representing 2 housing ages, 2 17% crude protein diets with and without added methionine and corn oil, 3 weight groups, and 2 light treatments 14L:10D and 14L:14D. Leghorn pullets were classified as heavy, medium, or light weight at either 15 or 19 weeks of age, and at those times, moved to individual laying cages maintained in rooms with either a 14L:10D or 14L:14D photoperiod. Birds were fed a conventional 17% CP corn-soybean diet or one containing additional methionine and corn oil. Each factorial treatment was represented by four replicate groups of seven consecutive individually caged birds. The trial was terminated at 71 weeks of age. Ahemeral lighting resulted in increased egg weight, body weight, and inferior shell quality, whereas egg production and feed intake were reduced (P<.01). Early transfer at 15 weeks resulted in loss of egg numbers (P<.01), while body weight at transfer was positively correlated with egg production, feed intake, and egg weight. Diet had no effect on production. In a second and third trial Leghorn pullets were reared on constant photoperiods of 8 or 14 hr. At 15 or 19 weeks of age, pullets were transferred to environments providing regular or ahemeral cycles as described for Trial 1. Again, pullets were classified according to weight and fed diets of low or high nutrient density. Both trials were terminated at 31 weeks of age. The effects of ahemeral lighting in Trial 2 on food intake, egg weight, egg production, and body weight were as described in Experiment 1, although in this situation eggshell quality was improved. Rearing birds on 14 vs. 8 hr photoperiods, in both trials, resulted in loss in egg numbers (P<.01), although egg weight was increased (P<.01). A final trial also involved rearing on photoperiods of 8 vs. 14 hr for weight-segregated pullets fed regular or high nutrient density diets. Adult photoperiod was a constant 14 or 17 hr, and again the trial was terminated at 31 weeks of age. Heavier pullets, at transfer time of 19 weeks, produced the greatest amount of eggs that were also larger (P<.01) while consuming more feed (P<.01). A rearing photoperiod of 14 vs. 8 hr reduced egg numbers (P<.01) while increasing egg size (P<.05) and body weight (P<.01). It is concluded that ahemeral lighting can be used to stimulate early egg size, although this is at the expense of egg numbers. While increasing the rearing photoperiod from 8 to 14 hr stimulates pullet growth, subsequent egg production is reduced, possibly due to the insufficient photostimulation at time of transfer.