Genome-wide association study of bone strength and body weight in commercial crossbred layer chickens
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Osteoporosis and bone fractures are a serious problem for the welfare of laying hens, with genetics making a substantial contribution to bone strength. The genetic basis of bone strength in chickens has previously been mapped in experimental intercrosses and within pedigree lines. We performed a genome-wide association study of tibial breaking strength and body weight in 860 commercial crossbred chickens from two different companies, kept in either furnished cages or floor pens.
As expected, the two production systems produced a large difference in bone breaking strength, where floor pen-raised chickens had stronger bones. Genome-scans either combining or independently analysing the two housing systems revealed no genome-wide significant loci for bone breaking strength. We detected three loci for body weight on chromosomes 4, 6 and 27, that were shared between the housing systems (either genome-wide significant or suggestive when the housing systems were analysed individually).
In summary, we found little evidence for large-effect loci for tibial breaking strength in commercial crossbred chickens, consistent with a highly polygenic architecture for bone strength in the production environment.