Shell Quality of Eggs from Hens Exposed to 26- and 27-Hour Light-Dark Cycles from 56 to 76 Weeks of Age

Abstract

The effect of ahemeral light-dark cycles on shell quality and laying hen performance near the end of the laying year was measured using 1342 Single Comb White Leghorn laying hens. The hens were housed in multiple-bird cages in 18 separate, windowless, fan-ventilated rooms. Hens were exposed abruptly to either a 26-hr cycle (16L:10D) or a 27-hr cycle (16L:11D) at either 56 or 60 weeks of age; a 26-hr cycle at 56 weeks, which was increased t o 27-hrs at 60 weeks of age; or remained on a 24-hr cycle (16L:8D) until the experiment was terminated at 76 weeks of age.Shell weight, and consequently shell quality, expressed as shell weight (mg) per square centimeter egg surface area (SWUSA), were significantly increased after 1 week exposure to either ahemeral cycle. The increase in shell weight was greatest for the hens on the 27-hr cycle, but because egg weight also was significantly increased by this treatment, there was no difference in SWUSA between the two ahemeral cycles. The magnitude of increase in shell weight and SWUSA, but not egg weight, was less in the hens exposed to the ahemeral cycles at 60 weeks of age. This was due to shell weight progressively decreasing with increasing age of the hens on all three light cycles. But SWUSA, irrespective of when the ahemeral cycles were initiated, was as great or greater through 72 weeks of age than SWUSA measured in these hens at 53 weeks of age prior to the experiment.The ahemeral cycles had no significant effect on albumen quality, rate of lay adjusted to a 24-hr basis, hen body weight, or mortality. There was a significant improvement in feed efficiency for the hens on the 27-hr cycle.