Effect of housing system on the calcium requirement of laying hens and on eggshell quality

The effects of housing systems on the calcium requirement for eggshell production, eggshell quality and on the breaking strength of the hen's tibia were evaluated. Unenriched cages (UN) (24 laying hens), enriched cages (EN) (16 laying hens) and floor system (FS) (24 laying hens) were used in this experiment. The eggshell production of laying hens from 19 to 66 weeks of age was higher (P < 0.01) in the cage systems (UN 39.6 g/hen/week and EN 39.2 g/hen/week) than it was in FS (35.0 g/hen/week). Consequently, the amount of calcium deposited in the eggshells (g/hen/week) was higher (P < 0.01) in the cage systems (14.2 and 14.0 g/hen/week) than in FS (12.6 g/hen/week). Despite of the same calcium intake of the hens housed in EN and FS the eggshell thickness (0.39 and 0.38 mm, respectively) and eggshell strength (38.04 and 36.43 N respect.) were higher (P < 0.01 and P < 0.001 respectively) in EN. The tibia breaking strength was higher (P < 0.05) in FS (156.6 N) in comparison with UN (92.7 N). The rate of calcium intake deposited in the eggshells was higher in the cage systems than in FS, namely by 1.7 to 8.9% depending on the age of laying hens. When determining the correct calcium requirements in the diets of laying hens, the housing system should be taken into account.