Effect of age, stocking density, genotype, and cage tier on feather score of layer pure lines

The objective of the study was to investigate the effect of genotype, age, stocking density, and cage tier on the feather score of egg-laying pure lines. The trial was carried out with five white (BLACK, BLUE, MARON, BROWN, and D229) and six brown (RIR1, RIR2, BAR1, BAR2, COL, and LINE54) eggshell lines as classified by the Ankara poultry research institute. In the experiment, 162 chicks were randomly selected from each of the 11 lines; thus, a total of 1782 chicks (810 and 972 white and brown layer pure lines, respectively). At 17 weeks of age, pullets were chosen at random and placed in 3-tiered battery-type cages. Each tier housed 99 chickens (11 lines, 3 different stocking densities, 3 replications). The stocking density was 5 birds, 6 birds, and 7 birds per cage cell that corresponded to 720 cm(2), 600 cm(2), and 514.28 cm(2) of floor space per bird, respectively. Feeding was ad libitum during the growth and egg production periods. Feather scores of the head, neck, breast, back, wings, and tail regions of the chickens were taken at the 30th, 40th, 50th, and 60th week of age. The results indicated that age, stocking density, cage tiers, and genotypes have a significant effect on the feather score of the head, neck, breast, back, wings, and tail; feather score significantly decreased at an increasing age and stocking density (p < 0.01). It was observed that the feather score of the chickens on the top tier was significantly increased (p < 0.01). It was found that RIR2, BLACK, and COL pure lines had the best feather score. These findings suggest that chickens placed in top cage tiers with low stocking density (5 chickens/cage cell) and RIR2, BLACK and COL pure line genotypes improve feather score.