Influence of different tiers in furnished cages and small group systems on production traits, mortality, egg quality, bone strength, claw length and keel bone deformities in layers

The objective of the present investigation was to analyse the effects of different tiers in furnished cages and small group systems on the parameters production, mortality, egg quality, bone strength, claw length and keel bone deformities. The investigation was conducted during one laying cycle (September 2003 - July 2004) in which laying hens from the commercial strain Lohmann Selected Leghorn (LSL) were equally distributed among the different housing systems and tiers. Half of the hens were raised on the floor while the other half was raised in cages. During the whole laying period the hens had identical feeding and management. It could be shown that the tier had a significant effect on the different parameters investigated. In the lower tiers of the small group systems a higher egg production per hen housed than in the upper tiers could be detected. In addition, the egg production per hen housed was lower in the 4th tier of the two small group systems compared to the other tiers. This was based on the higher mortality in this tier. Besides that it was remarkable that mortality was significantly higher for hens raised on the floor than for hens raised in cages. Furthermore, in all investigated housing systems egg shell density was lower in the 4th tier compared to the other tiers. This resulted in a higher proportion of cracked eggs in the 4th tier. Both humerus and tibia breaking strength were lowest in the 4th tier, although the differences were not significant. The claws of the hens from the 4th tier were longer than in the other tiers, whereas there were no significant differences among the tiers in keel bone deformities. Thus, it could be shown that housing hens in systems with more than three tiers requires higher demands to the management particularly with regard to productivity, animal health and welfare. Especially climatic conditions and light intensity should be considered.