# The Influence of Different Light Day Distribution in Hy-Line W36 Laying Hens on Egg Production and Egg Quality

## TL;DR

Interrupting darkness in laying hens' light schedules improves egg production and quality compared to continuous light and dark periods.

## Contribution

This study shows that scotophase interruption enhances eggshell quality and production in Hy-Line W36 hens.

## Key findings

- Hens with interrupted scotophase had higher egg production and fewer damaged eggs.
- Eggshell weight, thickness, and strength were better in treatment groups than in the control group.
- Eggshell quality remained consistent over time in treatment groups but declined in the control group.

## Abstract

Access to dietary calcium during eggshell formation may impact egg quality and laying-hen welfare. Our study aimed to determine the effects of interrupted darkness (scotophase) on egg quality parameters in laying hens. Hens were housed in pens exposed to either the commercial recommendation for light schedules (C; 16 h light/ 8 h darkness), 1 h of interrupted scotophase (W1; 15 h light/ 4 h dark/ 1 h light/ 4 h dark), or 2 h of interrupted scotophase (W2; 14 h light/ 4 h dark/ 2 h light/ 4 h dark) from 20 to 70 weeks of age. C hens exhibited lower daily egg production rates than W1 and W2 hens during peak and late lay phases. Additionally, C hens exhibited higher percentages of damaged eggs when compared to W1 and W2 hens in the mid- and late-lay phases, as well as lower eggshell weights, thicknesses, eggshell ash percentages, and eggshell strengths. An age effect was detected in measures of external quality for C hens in terms of shell thickness, ash percentages, and eggshell strength, whereas these parameters remained consistent for W1 and W2 hens across the weeks of the trial. An age effect was also detected in hen-day egg production for C, W1, and W2 hens.

Laying hens are commonly provided with 16 h of continuous light and 8 h of continuous darkness, with eggshell calcification largely developing during dark hours when dietary calcium is depleted simultaneously with the daily fasting period in laying hens. This phenomenon is thought to be the leading cause of osteoporosis in modern commercial flocks. This trial examined how disrupting the midnight phase affected egg quality in Hy-line W36 hens assigned to control (C) or treatment groups (W1 or W2) from 20 to 70 weeks of age. C hens received 16 h of light and 8 h of dark. W1 hens received 1 h of scotophase interruption, whereas W2 hens received 2 h of scotophase interruption. Across weeks, performance, production, and egg quality measures were measured (p < 0.05). Scotophase interruption displayed a positive effect on the treatment groups in terms of HDEP (week 50: p = 0.028, 0.016; week 70 = 0.031,0.022), damaged eggs (week 50: p = 0.012, 0.021, week 70: p = 0.019, 0.025), eggshell weight (week 30: p = 0.021, 0.027; week 50: p = 0.022, 0.024; week 70; p = 0.018, 0.019), eggshell thickness (week 30: p = 0.017, 0.022; week 50: p = 0.018, 0.031; week 70; p = 0.029, 0.033), ash percent week 30: p = 0.027, 0.021; week 50: p = 0.012, 0.014; week 70; p = 0.031, 0.034), and eggshell strength (week 30: p = 0.025, 0.023; week 50: p = 0.019, 0.021; week 70; p = 0.029, 0.015) in W1 and W2 birds compared to C birds.