Viability Influenced by Photoperiodic Treatment During Growth and Egg Production

Abstract

Reported herein are mortality data for two experiments involving a total of 1036 pullets of two commercial Leghorn-type stocks which were subjected to the following photoperiodic environments: (1) 6 hour-3% increment—six hours of daily light from day-old to 20 weeks of age, then three percent positive weekly increments through the laying year; (2) 14 hour-3% increment—fourteen hours of daily light through 50 weeks of age (about 30 weeks in production) and three percent weekly increments thereafter. Since the 6 hour-3% increment groups had reached 14 hours of light per day at 50 weeks of age, both treatment groups were thus continued on concurrent three percent programs until 24 hours of light was achieved at 68 weeks of age. In Experiment 2, due to a faulty electric timer, birds in the 6 hour groups received one period of 36 hours of continuous light at 14 weeks of age. In…