Do the their high prevalence (>90% within some flocks) and association with pain and decreased egg quality, the occurrence of keel bone fractures (KBF) in egg laying hens has been recognized as a major animal welfare issue in modern egg production (reviewed in Rufener & Makagon, 2020).  Keel fracture formation is affected by numerous factors, including breed, nutrition, genetics and housing.  Research conducted in our behavior and welfare lab has explored the influence of housing (both rearing and layer systems) on keel bone fracture formation.

 

Effects of early experiences on depth perception, space use, bone development and keel bone prevalence of aviary-housed hens. 

Project summary:

We led a multi-disciplinary project to test whether the opportunity to move through vertical space during rearing would enhance the birds’ performance on cognitive tasks (Jones et al., 2023), brain development (Pullin et al, 2022) use of 3-dimensional space (Pullin et al., 2024), bone development and keel bone fracture prevalence (Makagon et al., under review).  Pullets were raised in three types of pullet rearing housing that varied in vertical complexity (pens with low perches, single-tiered aviary, double tiered aviary). When the birds reached 17 weeks of age, pullet housing was replaced with multi-tiered layer aviary systems. We tested the impact rearing on the depth perception of individual birds at 7-8, 15-16 and 29-30 weeks of age. Cognitive tests were complemented with analyses of neural development in an area of the brain associated with spatial orientation and memory when hens were 16 weeks old. We evaluated the birds’ distribution across and movement up and down elevated spaces in their rearing and layer aviary housing at multiple ages, from 6 to 26 weeks old. We evaluated bone quality of the tibia, humerus and keel when the birds were 8 and 16 weeks old. Finally, we used x-rays to determine the presence and severity of keel fractures at 18, 26, 28 and 30 weeks of age.

Some results highlights:

  1. housing pullets with access to elevated spaces facilitated their transition to multi-tiered aviaries
    • Differences were found primarily birds that had been reared with the floor pens and those reared with one of the aviaries
  2. providing access to two-tiered vs. single-tiered aviaries during rearing did not further improve measured outcomes
    • Few differences were found between birds reared with single- versus two-tiered aviaries
  3. pullets raised without access to vertical space were more hesitant to utilize the multi-tiered aviary, however their depth perception was not affected
    • Birds from all treatments were able to discriminate depth, but those that had been raised with minimal access to height were less  likely to access the aviary upon introduction, and less likely/slower to move over virtual gaps on the cognitive test
  4. hens habituated quickly to their new multi-tiered aviary environments
    • Most, but not all, differences in observed at or near the time when pullets transitioned into the multi-tiered aviaries disappeared after birds gained experience with these systems
  5. rearing did not affect the quality of movement within the aviary, or keel bone fracture prevalence
    • Pullets were observed to make few uncontrolled movements while transitioning up and down the aviary
    • Keel bone fracture prevalence was high, in part due to the sensitivity of the fracture detection method

Available publications:

  1.  Journal articles:
    • Makagon, M.M., A.N. Pullin, C.B. Rufener, J. Tarlton, M. Toscano, R.A. Blatchford. Under peer review. Effects of pullet housing on bone development in aviary-housed Dekalb White hens. Poultry Science.
    • Pullin, A.N., C.B. Rufener, S.T. Millman, J.F. Tarlton, M.J. Toscano, R.A. Blatchford, M.M. Makagon. 2023. Providing elevated structures in the pullet rearing environment affects behavior during initial acclimation to a layer aviary. Poultry Science: 103357.
    • Jones, C.T., A.N. Pullin, R.A. Blatchford, M.M. Makagon, and K. Horback. 2023. Effects of rearing with vertical structures on the ontogeny of depth perception in laying hens. Applied Animal Behavior Science 259: 105837.
    • Pullin, A.N., V.S. Farrar, J.W. Loxterkamp, C.T. Jones, R.M. Calisi, K. Horback, P.J. Lein and M.M. Makagon. 2022. Providing height to pullets does not influence hippocampal dendritic morphology or brain-derived neurotrophic factor at the end of the rearing period. Poultry Science 101: 102161
    • Rufener, C. and M.M. Makagon. 2020. Keel bone fractures in laying hens: a systematic review of prevalence across age, housing systems, and strains. Journal of Animal Science 98(Suppl. 1): S36-51
  2. Graduate student dissertations & theses:
    • Pullin, A.N. 2022. The effect of pullet rearing environments on spatial abilities of laying hens. Ph.D. Dissertation, University of California, Davis
    • Graham, E.A. 2021. Resource Utilization by laying hen pullets when reared with access to varying vertical spaces. M.S. Thesis. University of California, Davis.
    • Jones, C.T. 2018. Effect of vertical complexity of rearing environment on the ontogeny of depth perception in laying hens. M.S. Thesis. University of California, Davis

Key funding sources

  • Research reported in this publication was supported by the Foundation for Food & Agriculture Research under award number – Grant ID: 550830. The content of this publication is solely the responsibility of the authors and does not necessarily represent the official views of the Foundation.
  • The research was further supported by in-kind donations from Lubing.
  • Additional funding was provided by Western Poultry Scholarship and Research Foundation and Henry A. Jastro Research Award (University of California, Davis), and funding related to the USDA Multistate Research Project NC1029.