Turkeys are seasonal breeders that require an increasing photoperiod to activate the reproductive axis. Research in other avian species has shown that red light has the greatest tissue penetration power, resulting in more effective deep-brain photoreceptor stimulation. Thus, housing poultry under red light improves reproductive performance, said Clara Ziezold, graduate student at the University of Guelph, Canada.

Based on the results of a pilot study, however, light intensity could be a confounding factor. A study evaluated the effects of white (W) or red (R) spectrum light at low (L; 0.1 W/m2) or high (H; 0.3 W/m2 ) intensity on the egg production performance of turkey breeder hens, she said.

At 20 weeks of age (woa), 402 female grandparent turkeys were randomly allocated to 24 pens within four rooms. Color was assigned by room and intensity by pen for a split-plot design. Intensity was harmonized to 0.1 W/m2 during the growth phase (20-29 woa). At photostimulation, intensity was increased to 0.3 W/m2 in three pens per room and photoperiod was increased as per the breeds guidelines. Egg production was recorded until 60 woa, Ziezold explained.

Throughout the experiment, body weight and egg quality parameters were measured every two and four weeks, respectively. Cumulative egg production did not differ significantly between treatments, with each hen producing 129, 129, 130 and 132 eggs under WL, WH, RL and RH, respectively, she said.

However, eggs produced under low intensity light were heavier and tended to have higher breaking strength. Egg yolk, shell and albumen also increased under low intensity light, although relative weights did not differ. This was likely an effect of increased body weight under low intensity light. Uniformity also tended to increase under low intensity light, she noted.

These results suggest that egg quality can be improved under low intensity light without compromising production. Further research should evaluate subsequent impacts on hatchability and poult quality, Ziezold concluded in her presentation at the 2024 International Poultry Scientific Forum.