Green light during incubation: Effects on hatching characteristics in brown and white laying hens

Providing light during incubation is being investigated as a method to improve welfare in later life in poultry. This incubation method would more closely approximate chicken natural environment compared to the current incubation in darkness. Previous studies showed promising results of light during incubation on broiler welfare, but little is known about effects of light during incubation on laying hens. Especially, information about its effects on hatching characteristics (hatch time, hatchability, chick quality, body weight and embryonic age of death) is scarce and requires investigation in both white and brown egg layers. In the current study, Dekalb White (DW) and ISA Brown (ISA) eggs were incubated in complete darkness (dark) or in a light:dark cycle of 12L:12D throughout incubation (light), resulting in four treatment groups: DW-dark, DW-light, ISA-dark, and ISA-light. In the light treatments, green LEDs of 520 nm wavelength were used, at an intensity of 400 lux. First, light transmission through the eggshell was measured through 27 eggs. Then, an analysis of the effects of light during incubation on hatching characteristics was performed on 711 chicks in two consecutive experimental rounds. Light transmission was higher through white eggshells than through brown eggshells (N = 27, p < 0.001). Light during incubation had no effects on hatching characteristics (N = 711, p & GE; 0.1). Despite the difference of light transmission through eggshell between hybrids, there was no interaction between incubation treatment and hybrid on hatching characteristics (N = 471, p & GE; 0.06). Hatch time was longer and navel quality was better in DW than in ISA, while body weight and embryonic age of death were lower in DW than in ISA (all p < 0.001). Males and females had similar chick quality scores except for the beak quality, which was better for males (N = 486, p = 0.003). To conclude, green light during incubation did not negatively affect hatching characteristics in either DW nor ISA laying hen hybrids. Future research should therefore focus on its potential benefits for laying hen welfare.