Characterisation of spermatozoal transcriptomes in sheep and the influence of breed and semen quality

Reproductive success, particularly after AI, is dependent on a number of contributing factors on both the ewe and ram sides. While there has been considerable emphasis on characterising ewe side contributions to reproductive success, relatively little emphasis has been placed on defining ram side contributors. In this context, the quality of semen used in AI is a crucial factor. Research details that spermatozoa contain around 14,000 mRNA transcripts (Selvaraju et al. 2017), which are transferred to the ova on fertilisation, conceivably influencing early embryonic development and successful conception. Therefore, this study aims to characterise the ovine spermatozoal transcriptome and investigate whether spermatozoal transcriptomes differ between breeds and between semen samples with high or low quality. Semen was collected (n=45) across three breeds; Merino, Dohne and Poll Dorset, and each ejaculate was subjected to computer assisted semen analysis (CASA) for assessment of quality parameters. RNA Sequencing and differential gene expression analysis identified 754 differentially expressed genes that were identified to play crucial roles in a variety of physiological functions, including fertilisation, embryonic development, and offspring production.