Testicular Biometry as a Non-invasive Indicator of Semen Quality and Sperm Kinematics in Black Bengal Bucks

Abstract

Scrotal circumference (SC) is widely used as an indicator of male reproductive potential; however, its predictive value for detailed seminal and kinematic characteristics remains poorly defined in Black Bengal bucks. This study evaluated the association of testicular biometry with semen quality and computer-assisted sperm analysis (CASA)-derived sperm motion traits in 15 clinically healthy bucks, retrospectively grouped by SC as 19–22 cm (Group I) and ≥22–25 cm (Group II). The results showed that bucks with larger SC had significantly greater testicular width, testicular volume and estimated testicular weight (P < 0.05), indicating greater testicular development. These biometric differences were accompanied by improved seminal attributes, including higher semen volume, sperm concentration, mass motility and sperm viability (P < 0.05). CASA evaluation further showed higher progressive motility and increased velocity and distance indices, including VSL, VCL, DAP and DSL, in Group II than in Group I (P < 0.05). Correlation analysis demonstrated stronger associations between SC, testicular measurements, semen volume and sperm concentration in bucks with SC ≥22 cm (r = 0.668–0.870; P < 0.05 or P < 0.01), whereas the corresponding relationships were weaker in bucks with smaller SC. Although the study was based on a modest sample size, the findings suggest that SC and related testicular biometric traits may serve as practical, non-invasive indicators of semen quality and sperm kinematics in Black Bengal bucks, supporting their use in preliminary breeding-male selection and AI-based genetic improvement programmes.