Defining optimal frame rate for kinematic semen analysis of different dog breeds assessed by computer-assisted sperm analysis

The development of computer-assisted sperm analysis (CASA) systems has expanded the number of analyzable seminal parameters. The aim of this study was to define the optimal frame rate analysis using CASA-Mot system, and to evaluate the effect of different dog breeds on the sperm kinematic variables measured. Ninety-seven ejaculates from 49 adult males of 11 dog breeds enrolled in an artificial insemination program were collected, extended and analyzed at 37 °C. Samples were obtained via manual stimulation at the Sangüeso Veterinary Clinic in Valencia, Spain, and were immediately analyzed using the ISAS^®v1 system. Videos were acquired at 500 frames per second (fps) and computationally down sampled to 25–400 fps. Sperm kinematic variables were modeled using an exponential regression to estimate the frame rate required to reach 95% of the asymptotic value. Curvilinear velocity (VCL) was the most frame-rate sensitive parameter. The optimal frame rate calculated from the kinematic variable VCL varied among breeds, ranging from 433.72 fps for the Miniature Schnauzer to 939.67 fps for the Golden Retriever. Furthermore, significant differences were found in all analyzed sperm kinematic parameters between breeds. Marked breed effects were detected in motility, concentration and kinematic patterns at 500 fps, with Jack Russell, French Bulldog, Giant Schnauzer and Golden Retriever showing the highest total and fast motility, and Dachshund and Miniature Schnauzer the lowest. Overall, dogs require higher frame rates than most domestic species for reliable CASA-based kinematic assessment, and breed effects should be considered in future research when interpreting canine semen data.