Layer performances, eggshell characteristics and bone strength in three different housing systems

The aim of this study was to determine the effects of three different housing systems for laying hens (cages, barn and organic) on layer performances, eggshell characteristics and bone strength. In each system, the same strain of laying hens (Hyline Brown\uae) was housed in agreement with current European regulation and the hens were fed on the same level of nutrition (2800 ME). The study was conducted over one year period in three typical farms in the north of Italy, from the 18th to the 70th weeks of layers age. The number of eggs collected and laid on the floor were recorded weekly, as well as the mortality and the feed consumption. At 27, 30, 35, 43, 53 and 68 weeks of layers age, the weight and the shell characteristics of eggs from the different systems were analysed. Bone breaking strength and stiffness were determined by three point bending test. The percentage of deposition was generally higher in comparison to the standard production of Hyline hens, probably, due to a high management standard and to the production persistence. The results indicated a clear relationship between the percentage of cracked eggs and the strength characteristics of the shells, with organic eggs showing the highest shell thickness, the most resistant shell and consistently the less cracked eggs. Considering the changes that occur during the laying cycle, shell strength and thickness in non-cage eggs were highly affected by hen age, while they were much stable in cage eggs. Organic hens also showed the strongest humerous, while their tibiotarsus were as robust as those of cage hens