Influence of different small-group-systems on performance traits, egg quality and bone breaking strength of laying hens 2nd communication:: Bone breaking strength

In the present investigation the effects of furnished cages and small-group-systems on the humerus and tibia breaking strength of two different layer lines were analysed in two trials. Each housing system contained of two different group sizes. In the first trial a white layer line (Lohmann Selected Leghorn: LSL) and a brown layer line (Lohmann Brown: LB) both reared in cages were equally distributed among the different housing systems but not mixed within a cage. In the second trial only a white layer line (LSL) was analysed, but this time half of the hens were reared in cages and the other half on the floor. Throughout the whole laying period the hens had identical feeding and management. In total 852 humerus bones and 855 tibia bones were analysed. The LB-layer line showed a higher humerus breaking strength than the LSL-layer line. Considering the different rearing systems, the LSL-hens reared in cages showed higher humerus and tibia breaking strengths than the LSL-hens reared on the floor. Between the investigated housing systems there were only few differences in bone breaking strength. The LB-layer line showed significantly higher humerus breaking strengths in the system Aviplus compared to the two small-group-systems. The bone breaking strength in the different group sizes did not significantly differ. Hens in all investigated housing systems showed a clearly higher bone breaking strength compared to conventional cages. Furthermore, the breaking strengths of the present investigation were partly comparable to those from aviary systems and free range systems. Therefore it could be reasoned that, concerning bone breaking strength, furnished cages and small-group-systems are an improvement of conventional cages and furthermore they could function as an alternative to extensive housing systems like aviary or free range.