Lordosis and/or kyphosis in pigs: testing the hereditary hypothesis

Lordosis and/or kyphosis, also called ”dipped shoulder” or ”humpy‐back” is sporadically observed in growing pigs. This condition is characterized by a thoracic and/or lumbar spinal deformity. Pathomorphologically, it may be comparable with Scheuermann’s kyphosis in man and so constitutes a spontaneous model for this humane kyphosis of the thoracic or thoracolumbar spine. In pigs, this condition may decrease the value of carcasses, making deboning efforts challenging. Three major and non‐exclusive hypotheses formulated to explain these back deformations are nutrition, intrauterine viral infection and inherited predisposition. The objective of the present study was to test the latter and, if possible, to identify a locus (some loci) associated with the affection. Forty‐eight pigs were included in this case‐control study. Based on a clinical examination and/or on a measure of the degree of spinal deformity, 25 pigs classified as affected were compared to 23 pigs considered as normal. A whole genome Single Nucleotide Polymorphism (SNP) analysis was performed using a 50,000 SNP array. DNA from forty‐seven samples (tail tissue or blood) was extracted while one sample was eliminated because of its poor quality. After applying quality controls, 40 pigs and 57,838 SNPs (on a total of 62,163) remained for further analysis. One SNP (ASGA0090747) located on Sus scrofa chromosome SSC8 crossed the genome‐wide significant threshold and is thus suspected of being associated with the lordosis and/or kyphosis phenotype. These results seem to confirm the hereditary hypothesis. Further investigations are however needed to confirm the suspected association