CCDC174 Gene Expression as a Molecular Marker of Bull Fertility

Abstract

Conventional semen evaluation methods do not fully capture molecular differences among ejaculates with similar motility profiles. The CCDC174 gene has been associated with sperm motility and fertility in dairy bulls, but its predictive value across breeds under field classification systems remains unclear. This study evaluated whether CCDC174 expression differs between fertile and sub-fertile ejaculates and whether it predicts progressive motility. A total of 53 ejaculates from nine bulls of three dairy breeds (Friesian, Ayrshire, and Jersey) were analyzed at the National Artificial Insemination Centre, Tanzania. Ejaculates were classified as fertile or sub-fertile based on progressive motility . CASA was used to assess sperm kinetics. CCDC174 expression was quantified using qPCR, with GAPDH as the reference gene. Associations between variables were analyzed using appropriate statistical tests, and a linear mixed-effects model was used to evaluate predictors of progressive motility. Most ejaculates (81.1%) were classified as fertile. CCDC174 expression differed significantly between fertile and sub-fertile groups. Progressive motility was associated with breed and gene expression in unadjusted analysis. In the mixed-effects model, CCDC174 expression and specific sperm kinetic parameters were significant predictors of progressive motility, while breed and season were not significant after adjustment. The study concludes that CCDC174 gene expression is associated with sperm progressive motility and independently predicts fertility-related parameters beyond conventional semen evaluation. These findings support its potential use as a complementary molecular marker in bull fertility assessment.