Overall objective
- Advance understanding of the bone biology of laying hens and identify practices for housing and managing of different strains of pullets that result in a successful adaptation to a complex housing environment and a healthy hen to end-of-lay.
Specific objectives
- Compare the effects of different styles of commercial rearing aviaries on activity patterns, locomotory abilities, behavioural characteristics and musculoskeletal development of different strains of pullets.
- Determine the effect of light intensity on activity patterns, locomotory abilities, behavioural characteristics and musculoskeletal development of different strains of pullets housed in a non-cage system.
- Determine the effect of transitioning between different housing systems on wing muscle strength, keel bone fracture, energetic costs of locomotion and injury, and fear of injury.
- Observe the effects of age, strain, exercise and circadian rhythm on skeletal mechano-responsiveness, calcium homeostasis and bone quality.
Outcomes
- The results show consistent strain differences with the white-feathered LSL (Lohman Select Leghorn lite) performing better and succeeding more in tests of locomotion skills than the brown-feathered LB (Lohman Brown lite), and an improvement of locomotion skills with increased complexity during early life.
- These results confirm that birds perform more dynamic load bearing (dlb) in more complex aviaries and LSL perform more dlb than LB.
- Rearing aviary design can promote different dynamic and wing involved load bearing activities, which will have varying effects on bone strength and subsequent fracture risk.
- These results showed that the complexity of rearing housing reduces fearfulness in laying hen pullets, while the effect of genetic strain seems dependent on the frightening stimulus.
- Laying hen spatial skills appeared to be sensitive to the degree of early life complexity as well as genetic strain; genotype environment interactions indicated that the white pullets benefitted more from greater environmental complexity than brown pullets.
- These results indicate that rearing housing affected the well-being of hens throughout their lives and that both genetic strain and rearing complexity should be considered to improve laying hen welfare.
- Keel bone fractures do not impact energy expenditure when measured by flow-through-respirometry and doubly labelled water.
- A wing-assisted incline running exercise regimen during rearing benefits adult laying hens during aerial descent.
- Breed and loading history influence in vivo skeletal strain patterns in pre-pubertal female chickens.
- Rearing aviary housing contributed to the development of larger, stronger, and therefore potentially healthier bones in pullets.
- White birds tended to have proportionally longer, stronger bones than brown, likely making them better physically suited to life in aviary housing.
- The effect of loading on medullary bone parameters was influenced by strain. Our results surprisingly show a negative effect of in vivo loading on bone microstructure in both cortical and medullary bone.
- Results of the study comparing the behaviour and skeletal characteristics of pullets reared in different light intensities suggest that pullets can safely navigate through a complex environment at 10, 30 or 50 lux light intensity.
- Increasing the intensity to 50 lux may increase bird activity, and may increase preening behaviour, which can be indicative of positive well-being.
Application
- This knowledge provides valuable information to farmers regarding how to maximize bone formation in response to mechanical stimuli in terms of exercise and housing conditions for different genetic strains of laying hens.
- It also informs farmers on rearing systems for pullets that result in birds that are less fearful, more physically fit and are quicker to learn new tasks. These hens will be more adaptable and better suited for non-cage, and especially, aviary systems.
- These results may also be used to inform future codes of practice for laying strain pullets.
Principal Investigator
Tina Widowski, University of Guelph; Karen Schwean-Lardner, University of Saskatchewan; Bettina Willie, McGill University
Year the work was done
2018-2023
Source: Poultry Science Cluster
