Is Range Usage at the Onset of Egg Production Associated with Tibial Bone Mineral Density at the End of Lay?

Osteoporosis in laying hens is of health, welfare, and economic concern. During the onset of lay, hens rapidly build up the amount of medullary bone which has less structural integrity instead of structural bone formation (Whitehead, 2004). However, freedom of movement in cage free systems can stimulate structural bone formation to avoid mechanical failure which may improve bone health at the end of laying period. The aim of this study was to compare the ultrastructure features in laying hen tibia and to compare these parameters in hens with different range usage.

A total of 1,875 Lohmann brown hens were housed on a commercial farm amongst 40,000 other hens in an aviary system. These 1,875 hens were individually monitored for their range usage from 18 to 72 weeks. At week 22, hens were grouped into “stayers” (hens that had ranged 2.10 ± 0.7 days), “roamers” (hens that had ranged 8.20 ± 0.7 days), and “rangers” (hens that ranged 15.30 ± 1.0 days) and placed in separate pens (treatment groups) based on the previous 4 weeks of range use. At 72 weeks, 176 left tibiae of the hens were randomly collected and individually scanned using a GE-Phoenix V|tome|xs 240 micro CT scanner (GE Sensing & Inspection Technologies GmbH, Wunstorf, Germany) to determine various parameters (Table 1). Parameters were compared using a one-way ANOVA.

Ranging at the onset of lay did not affect any volumetric measures of bone quality. Further investigation about the possible contribution of hen movement within the aviary system, the impact of range usage on egg shell quality, as well as on other mineralisation parameters such as keel bone damage should be investigated.

ACKNOWLEDGEMENTS: This research was funded by Australian Eggs and the Poultry CRC, established and supported under the Australian Government’s Cooperative Research Centres Program.