Effects of photoperiod and filtered light on growth, reproduction, and mating behavior of turkeys. 1. Growth performance of two lines of males and females.

This study was designed to determine the effects of photoperiod and filtered light on growth of male and female turkeys. Large White (LW) and Medium White (MW) turkeys were reared under intermittent (2 h light: 2 h dark) or diurnal (12 h light: 12 h dark) photoperiods using white light, red (650 nm), or blue (450 nm)-filtered lights. Both males and females grew more rapidly under blue light than under red or white light up to 16 wk of age. After that age, rates of gain were significantly better under the white and red lights. Growth rates were significantly greater under the intermittent than under the diurnal photoperiod for both lines and sexes in Experiment 1 but not in Experiment 2. The greatest acceleration in growth rate was observed from 4 to 10 wk of age, with this advantage still evident at 24 wk of age. No significant differences in feed efficiency due to photoperiod or light color occurred. Early mortality was highest under blue light but late mortality was greater under red and white light. Mortality was higher for the LW than MW birds. Live grades were unaffected by light regimen or light color, but feather condition was poorest for birds reared under the white diurnal photoperiod.