The role of ß-defensin 103 (DEFB103) copy number variation in bull fertility

Pregnancy rates for elite bulls used in artificial insemination (AI) can vary significantly and therefore the identification of molecular markers for bull fertility and targets to improve bull selection is important. ß-defensins are peptides with diverse regulatory roles in sperm function across multiple species. To explore the functional impact of DEFB103 CNV on the uterine response in vivo, 18 heifers were inseminated with sperm from bulls categorized by low, intermediate, and high CN levels. Transcriptomic analysis of uterine tissue collected 12 hours after insemination revealed significant differential expression of 58 genes (FDR<0.1) related to sperm migration, immune signaling, and chemotaxis. These findings highlight the significant role of DEFB103 CN in both sperm function and the uterine response to bull sperm, suggesting its potential influence on pregnancy outcomes in cattle.