Loci associated with bone strength in laying hens

Sammanfattning: One of the growing welfare concern in the layer industry is the high incidences of bone fracture. This is thought to result from reduction in bone strength due to osteoporosis which is exacerbated by environmental stresses and mineral deficiencies. Despite these factors however, the primary cause of bone weakness and the resulting fractures is believed to be genetic predisposition. In this study, we performed a genome-wide association study to identify with high reliability the loci associated with bone strength in laying hens. Genotype information and phenotype data were obtained from 752 laying hens belonging to the same pure line population. These hens were genotyped for 580,961 single nucleotide polymorphisms (SNPs) with each of the SNPs associated with tibial breaking strength using the family-based score test for association (FASTA). A total of 52 SNPs across chromosomes 1, 3, 8 and 16 were significantly associated with tibial strength with the genome-wide significance threshold set as a corrected p.value of 10e-5. Based on the local linkage disequilibrium around the significant SNPs, 5 distinct and novel QTLs were identified on chromosomes 1 (2 QTLs), 3 (1 QTL), 8 (1QTL) and 16 (1 QTL). The strongest association was detected within the QTL region on chromosome 8 with the most significant SNP having a corrected p.value of 4e-7. A number of candidate genes were identified within the QTL regions, including the BRD2 gene which is required for normal bone physiology. Bone-related pathways involving some of the genes were also identified including the hedgehog signalling and Wnt signalling pathways. Our result supports previous studies, which suggested that bone strength is highly regulated by genetics. It is therefore possible to alleviate bone fracture in laying hens through genetic selection, and ultimately improve hen welfare.