DNA methylation analysis in sperm from boar with bad sperm quality Infertility problems are an increasing health challenge in human and animal populations. They can be explained by genetic or hormonal causes but also by aging or life‐style causes. In farm animals high inbreeding levels, exposure to atmosphere, food and water contaminants, also lead to a significant decrease of animal fertility and are beginning to be a real problem. For example, nearly 50% of boars selected on agronomical criteria (like growth or alimentary efficiency, muscle fat content…) are culled for bad sperm quality (including concentration, morphology and motility). In the present work we decided to focus our study on DNA methylation levels in sperm from boars with bad semen quality. DNA methylation is a direct modification of cytosine residues that can affect gene expression and chromatin organization. In infertile patients, sperm DNA methylation is affected at some particular loci especially those submitted to parental imprinting. Using the genomic and bioinformatics facilities available in our laboratory, we started to perform genome‐wide methylome maps from sperm DNA of fertile animals. At the same time, we looked at the methylation status of imprinted loci in sperm from animals with bad sperm quality using immunoprecipitation and real time PCR analysis of methylated DNA. Methylation of blood genomic DNA will also be analyzed at these loci to test for the presence of a positive correlation between DNA methylation defects in somatic and germinal cells. We hope to develop an easy diagnostic method to detect, in immature animals, future reproductive limitations.