Consequences of early life nutrition on bull sperm DNA methylation profiles post puberty

As diet can influence DNA methylation profiles in sperm, the objective of this study was to ascertain if early life calf nutrition could influence DNA methylation patterns in sperm produced post-puberty. Holstein-Friesian calves were assigned to a high (H) or moderate (M) plane of nutrition for the first 24 weeks of age, then reassigned to the M diet until puberty, resulting in HM and MM groups. Sperm DNA methylation patterns from subgroups of bulls in the HM (15 months of age; n= 9) and in the MM (15 and 16 months of age; n = 7 and 9, respectively) were obtained using reduced representation bisulfite sequencing (RRBS). Both 15 and 16 months were selected in the MM treatment as these bulls reached puberty approximately 1 month after the HM bulls. Hierarchical clustering demonstrated that inter-individual variability unrelated to diet or age dominated DNA methylation profiles. While the comparison between 15 and 16 months of age revealed almost no change, 491 differentially methylated CpGs (DMCs) were identified between the HM and MM groups. DMCs were mostly hypermethylated in the HM group, and enriched in introns, intergenic regions and shores and shelves of CpG islands.