Differential Sperm Kinematic and Functional attributes in High- and Low-Fertility Indigenous Cattle Bulls: A Comparative Analysis

Abstract

Accurate prediction of bull fertility remains challenging because conventional semen evaluation may not fully reflect the functional competence of spermatozoa. This study evaluated the association between sperm kinematic and functional attributes and fertility in indigenous Sahiwal breeding bulls. Cryopreserved semen straws from 12 bulls with recorded field conception rates were analysed. After correction for non-genetic factors, bulls were classified as high-fertility (n = 6; mean CR = 53.65%) or low-fertility (n = 6; mean CR = 34.79%). Sperm kinematics were assessed using computer-assisted sperm analysis, and DNA fragmentation was evaluated using sperm chromatin structure assay-related assessment, while functional attributes were assessed using flow cytometry. High-fertility bulls showed higher total motility, progressive motility, straightness, linearity, wobble and beat-cross frequency, with total motility and wobble differing significantly between fertility groups. Among functional attributes, viable spermatozoa, live calcium-negative spermatozoa and live acrosome-intact spermatozoa were higher in high-fertility bulls, whereas low-fertility bulls showed higher dead spermatozoa, dead acrosome-reacted spermatozoa and DNA fragmentation index. Correlation analysis indicated that total motility, LIVE (%), LAI (%), LIVE Ca⁻Ve (%) and DFI (%) were among the clearest fertility-associated measures. The findings indicate that a combined evaluation of sperm kinematics, viability, membrane status, acrosomal status, calcium status and chromatin integrity may provide a more informative assessment of cryopreserved Sahiwal bull semen than conventional evaluation alone.