Effect of genotype and housing system on egg production, egg quality and welfare of laying hens

Abstract

The aim of this work was to evaluate production traits, egg quality parameters and welfare indicators of two strains of layers (Hisex White and Hy Line Brown) kept in different housing systems. In each housing system both strains of layers were housed and that made 6 treatments in 2 × 3 factorial design (2 genotypes × 3 cage types). A) conventional battery-cages with 5 hens per cage providing 500 cm2 of floor space per bird (n = 180 (90 white and 90 brown layers), 36 cages in total, 5 hens/cage, floor space = 500 cm2/hen); B) enlarged battery-cages with 5 hens per cage providing 650 cm2 of floor space per bird (n = 120 (60 white and 60 brown layers), 24 cages in total, 5 hens/cage, floor space = 650 cm2/hen); C) enriched cages with 60 hens per compartment providing 750 cm2 of floor space per bird (n = 360 (180 white and 180 brown layers), 6 cages in total, 60 hens/cage, floor space = 750 cm2/hen). Examination of egg quality parameters was carried out in 8 four-week periods, starting from 32 weeks of age on the random sample of 30 eggs per treatment. Condition of feathers ware evaluated by scoring system at the end of the production cycle (70 weeks of age), and at the same time duration of tonic immobility was measured. The results showed that white layers in conventional cages achieved the best production results. The highest number of eggs was achieved with white layers in B and the lowest with the brown layers in C. White layers laid considerably more eggs compared to brown layers and had the best shell quality in all of the three housing systems. The birds in enriched cages laid significantly less eggs compared to other two cage types. The worst feather condition at the end of the production cycle was noticed in conventional cages (A) in both hybrids. Generally, brown layers suffered from more severe feather damage in all cage types compared to the white layers. The results showed a significant effect of cage type (p<0.01) and hybrid type (p<0.05) on duration of tonic immobility (TI) indicating that fearfulness of the birds was highly affected by housing system and genotype. Birds from both genotypes kept in conventional cages showed a shorter duration of TI than the birds kept in enriched cages and the white layers showed longer duration of TI than the brown layers.