Reference values for sperm motility and morphology using computer-assisted sperm analysis; insight in four inbred mouse strains

Abstract Genetic background can influence the reproductive performance in laboratory mice, yet strain-specific reference values for sperm motility and morphology remain limited. In this study, we used computer-assisted sperm analysis (CASA) to examine epididymal sperm from 40 males of each of four inbred strains: C57BL/6J, C57BL/6N, BALB/c, and CBA/J, with the aim of establishing strain-specific reference ranges and cut-off values for key motility and morphometric parameters. Marked inter-strain differences were observed in all major motility categories and in most kinematic parameters, with C57BL/6N generally showing the highest motility values and CBA/J the lowest. Strain-specific differences were also evident in sperm head and midpiece morphometry, with CBA/J showing the largest heads and BALB/c the smallest. Reanalysis using strain-specific morphometric values allowed the definition of normality cut-offs for each background. These data provide standardized reference ranges for sperm motility and morphology in four widely used mouse strains and support the use of strain-adjusted thresholds for reproductive phenotyping, cryopreservation quality control, and the assessment of genetically altered mouse lines.