Evaluation of bone strength, keel bone deformity and egg quality of laying hens housed in small group housing systems and furnished cages in comparison to an aviary housing system

Abstract. The objective of the study was to assess bone breaking strength, keel bone status and egg quality parameters of Lohmann Silver (LS) and Lohmann Tradition (LT) layers housed in small group systems (SG) and furnished cages (FC) in comparison to an aviary system. At the end of the 3rd, 6th, 9th and 11th laying month, approximately 40 hens were randomly chosen from each housing system and slaughtered (478 hens in total). Humerus and tibia strengths were analysed using a three-point-bending machine. Keel bone status was evaluated on a scale from 1 (severe) to 4 (no deformity). Shell breaking strength was measured every four weeks, totalling 4,887 eggs. Statistical analyses were performed using the MIXED procedure of SAS. Humerus and tibia strengths of LS layers housed in SG were significantly higher compared to LS hens kept in FC. Bone breaking strengths of humerus and tibia in LS and LT layers were highest in the aviary system and the differences to the other housing systems were significant. No significant differences in tibia and humerus bone breaking strengths were found between SG and FC for LT hens. Keel bone status was not significantly influenced by housing system or laying strain. For both hybrids, shell breaking strength was significantly lower in SG compared to FC and aviary system. The results showed that SG systems can significantly enhance bone breaking strength for LS layers in comparison to hens kept in FC. The lower shell breaking strength of eggs in SG might slightly impair economic aspects.