Transcriptomics Reveals L-Carnitine to Enhance Semen Quality in Malabari Bucks via Nutrigenomic Regulation of Key Biological Processes Associated With Male Fertility.

Male infertility poses a significant challenge in animal breeding, impacting genetic progress and reproductive efficiency. This study investigated the effects of L-carnitine supplementation (300 mg/kg basal diet for 105 days) on semen quality and underlying molecular mechanisms in Malabari bucks using a transcriptomic approach. Eight mature bucks (2-3 years) were randomly divided into control and treatment groups (n = 4 each). Semen parameters like semen volume (mL), concentration (106/mL), viability (%), abnormality (%), acrosome integrity (%), plasma membrane integrity (%) and oxidative stress via the Nitro Blue Tetrazolium (NBT) assay were evaluated. For transcriptomic analysis, sperm RNA was isolated, sequenced on the Illumina NovaSeq 6000 platform (150 bp paired-end), and differentially expressed genes (DEGs) were identified using DESeq2. Functional annotation was performed through GO enrichment and KEGG pathway analysis, whereas hub genes were identified via protein-protein interaction (PPI) analysis using STRING and Cytoscape. A total of 425 DEGs were identified, with 258 upregulated and 167 downregulated. Significant improvements were observed in acrosomal integrity, plasma membrane integrity, and oxidative stress markers following L-carnitine supplementation. GO enrichment analysis suggested upregulation of biological processes associated with meiotic cell division, sperm structural integrity, DNA repair, and spermatogenesis, alongside downregulation of carbohydrate metabolism pathways and a possible shift toward fatty acid oxidation. KEGG pathway analysis indicated upregulated Polycomb repressive complex pathway, and downregulation of insulin resistance and oestrogen signalling pathways, potentially creating a favourable endocrinological environment for male fertility. The hub genes identified, namely PMS1, ZFAND4, MYSM1, EEFSEC and CEP126, were found to be associated with key processes in male fertility. These findings provide preliminary mechanistic insights into L-carnitine's potential therapeutic role in small ruminant reproduction, and further functional validation of the identified hub genes is warranted.