Keel bone fracture, damage common among end-of-lay hens
MedWire News: Study findings show that current housing system designs used for keeping end-of-lay hens are associated with high levels of keel bone breakage and damage, with multilevel perches resulting in the highest levels of damage.
"Bone breakage in laying hens is a major welfare and economic problem for the poultry industry and particularly damages the public perception of large-scale egg production… however, there is no systematic information available about whether fracture incidence is significantly influenced by housing system or, critically, the structures within those systems," say LJ Wilkins (University of Bristol, UK) and colleagues.
To investigate, Wilkins and team assessed end-of-lay hens in 67 flocks housed in eight broad subcategories for keel fractures and breaking strength of the tibia, humerus, and keel bones. Main categories included free-range, organic, barn, and furnished cage, with differences seen in the provision of aerial perches.
Postmortem analyses of keel damage were assessed using a five-point photographic scale in addition to a severity scale ranging from 0 (no fracture) to 4 (severe or multiple damage sites). Linear modeling was then used to assess the relationship between fracture rates, bone strength, and individual elements of housing-system design.
The researchers found that keel damage for flocks housed in non-cage systems and furnished cages ranged from 30% to 95% and 15% to 55%, respectively. Flocks housed in furnished cages had a significantly lower prevalence of broken keels than those housed in organic static and other system types, except organic mobile sheds.
Keel damage was significantly greater among flocks housed with aerial suspended perches compared with non-perch systems, A-frame perches, and organic mobile housing with aerial perches (OMAF).
Furthermore, flocks housed in the OMAF system sustained significantly more damage than those without perches. Installation of an aerial perch was associated with a mean increase in damage prevalence from 46% to 80%.
Analysis of bone strength showed that furnished cages were associated with lowest bone-breaking strength, while birds housed in organic systems showed the highest breaking strength.
Writing in the journal Veterinary Record, the researchers conclude: "The layout of the internal environment, including access to the range, needs to be carefully considered in terms of its potential for ease of safe movement throughout all areas and the introduction of improved designs of included structures which not only meets the requirements of legislation and assurance schemes, but which adequately and safely meet the requirements of the birds themselves."
By Ingrid Grasmo