Genetic markers associated with bone strength and density in Rhode Island Red laying hens

Damage to the keel bone in commercial laying hens represent one of the greatest welfare issues in laying hens. This study aims to identify the DNA markers and candidate genes for bone strength and density traits in a Rhode Island Red laying hen population. We conducted genome-wide association studies (GWAS) on bone quality traits using a sample of 925 Rhode Island Red laying hens genotyped with a genotyping array consisting of 60 000 DNA markers. With a univariate linear mixed model, we identified 52 suggestive genetic markers located within 28 candidate genes that are associated with the humerus, keel, and tibia strength and density. We also found overlaps between the GWAS results for medullary bone score and tibia strength and density with published quantitative trait loci (QTL) for eggshell effective layer thickness and abdominal fat weight, respectively. Heritability estimates for the humerus stiffness, tibia stiffness, medullary bone score and minor bone diameter ranged from 0.21 to 0.34. Annotation term enrichment analysis of genes within 2 Megabases of suggestive markers found that mTOR signalling pathway, tryptophan metabolism, TGF-β signalling pathway, and apoptosis were significantly enriched. These loci do not overlap previously published associations, and thus appear to be novel.