Association study between β-defensin gene polymorphisms and mastitis resistance in Valle del Belice dairy sheep breed

Mastitis is generally caused by bacteria, and it is the most common disease in livestock species. Defensins are peptides with a broad spectrum of antimicrobial activity and β-defensin genes have been studied in several livestock species due to their important role in the innate immune response. The aim of this study was to establish an association between polymorphisms in the β-defensin 1 and 2 genes and mastitis resistance in the Valle del Belice dairy sheep. Data consisted of 1855 and 2804 observations for case and control group, respectively. Six single nucleotide polymorphisms and seven haplotypes were selected for association studies with mastitis. In particular, polymorphism G1747A on β-defensin 1 gene was associated with susceptibility to mastitis, while polymorphism G1659A on β-defensin 2 gene was associated with resistance to mastitis. Haplotypes ACAGGG and GCAGGG were associated with resistance to mastitis, whereas haplotype ACGGGG was associated with susceptibility to mastitis. The present study has firstly suggested the possible associations of β-defensin gene polymorphisms with mastitis resistance traits and showed the presence of interesting haplotypes in Valle del Belice dairy sheep breed. Results from association analysis provided preliminary evidence that β-defensins could be used as candidate genes or molecular markers for the improvement of ovine mastitis resistance traits in Valle del Belice dairy breed.