Semen Analysis

The reproductive efficiency of livestock is crucial for agricultural productivity and economic sustainability. One critical factor in successful fertilization and the viability of offspring is the quality of semen. Poor semen quality, especially in frozen-thawed semen used in artificial insemination (AI) have been shown to influence conception outcomes, resulting a negative impact on livestock production. Recent advancements in genetic research have identified specific markers linked to semen quality traits in various livestock species, such as cattle, sheep, goats, pigs, buffalo, and equines. These genetic markers are essential in screening males for breeding suitability, which in turn enhances selective breeding programs. Understanding these markers is crucial for improving reproductive performance and increasing productivity in livestock populations. This review offers a comprehensive overview of the genetic markers associated with semen quality in key livestock. It explores the underlying genetic mechanisms and their practical implications in animal breeding and management. The review underscores the importance of integrating genetic insights into breeding strategies to optimize reproductive efficiency and ensure the sustainable development of livestock industries.

In briefSperm function is essential for fertility across humans, agriculture and wildlife, yet comparative studies remain limited. This study integrates multi-species proteomic data to identify a core sperm proteome, uncovering conserved molecular pathways and validating novel sperm proteins critical for motility and fertilization.AbstractReproductive biology is often considered in three siloed research areas; humans, agriculture and wildlife. Yet, each demand solutions for treatment of subfertility, fertility biomarkers, development of assisted reproductive technologies and effective contraception. To efficiently develop solutions applicable to all species, we must improve our understanding of the common biology underpinning reproductive processes. Accordingly, we integrate proteomic data from 29 publicly available datasets (>2 TB of data) to characterize mature sperm proteomes spanning 12 vertebrate species, identifying 13,853 proteins. Although human and mouse have relatively well-annotated sperm proteomes, many non-model species rely heavily on predicted or homology-inferred identifications. Despite variation in proteome size, composition and reproductive strategies, comparative analyses revealed that vertebrates share a fundamental molecular framework essential for sperm function. A core set of 45 species-level and 135 order-level conserved proteins mapped to critical processes, including energy generation, acrosome function and novel signalling pathways (BAG2 and FAT10). Knockout mouse models further validate the significance of these conserved proteins, demonstrating that their disruption impairs sperm motility and fertilization capacity. Moreover, we discovered loss-of-function variants of two additional core sperm proteins in clinical samples, linking them to severe sperm defects. Intriguingly, in-silico analysis reveals function-driven, context-dependent diversity surpassing evolutionary patterns. Collectively, these results highlight the value of integrating publicly available datasets and underscore the need for improved genome/proteome annotation in non-model species in mammals. This work provides a foundation for developing cross-species strategies to enhance fertility treatments, assisted reproductive technologies and conservation efforts. All data are available via ShinySpermKingdom (https://reproproteomics.shinyapps.io/ShinySpermKingdom/).

Transcriptionally and translationally silent sperm undergo functional maturation during epididymis traverse, which provides sperm ability to move and is crucial for successful fertilization. However, the molecular mechanisms governing sperm maturation remain poorly understood, especially at the protein post-translational modification level. In this study, we conducted a comprehensive quantitative phosphoproteomic analysis of mouse epididymal sperm from different regions (caput, corpus, and cauda) to unveil the dynamics of protein phosphorylation during sperm maturation. We identified 6447 phosphorylation sites in 1407 phosphoproteins, and 345 phosphoproteins were differentially phosphorylated between caput and cauda sperm. Gene ontology and KEGG pathway analyses showed enrichment of differentially phosphorylated proteins in energy metabolism, sperm motility, and fertilization. Kinase substrate network analysis followed by inhibition assay and quantitative phosphoproteomics analysis showed that TSSK2 kinase is important for sperm motility and progressive motility. This study systemically characterized the intricate phosphorylation regulation during sperm maturation in the mouse epididymis, which can be a basis to elucidate sperm motility acquisition, and to offer potential targets for male contraception and the treatment of male infertility.

Semen quality serves as a vital indicator of male fertility, yet its underlying genetic and regulatory mechanisms remain poorly understood. Here, 1.15 million records of six semen quality traits from 14 210 boars in four distinct breeds were collected. These traits have low to moderate heritability (0.12-0.26), and are genetically correlated with growth traits like average daily gain. Genome-wide association study (GWAS) and multi-breed meta-analysis detected 234 loci associated with semen quality. Systematic integration of the Pig Genotype-Tissue Expression resource with these GWAS loci allowed the prioritization of 93 causal variants targeting 134 genes. For instance, the expression quantitative trait loci (eQTL) of NAXE in multiple tissues were colocalized with a GWAS loci of the number of sperms, while eQTL of LEFTY2 in the testis was exclusively colocalized with in a GWAS loci of semen volume. Through examining GWAS of semen quality traits in cattle and human complex traits, the ortholog genes (e.g., AURKAIP1 and ADRA2A) significant in pigs also regulated bovine semen quality, and were significantly enriched for heritability of human birth weight and height. This study provides novel insights into semen quality traits in mammals, which will provide candidate genes for pig selective breeding and potential targets for human male infertility research.