Computer-Assisted Sperm Analysis in Dogs and Cats: An Update after 20 Years T Rijsselaere 1 , AVan Soom 1 , D Maes 1 and W Nizanski 2 1 Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; 2 Department of Reproduction, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland Contents In dogs and cats, computer-assisted sperm analysis (CASA) was originally described almost 20 years ago. Subsequently, numerous CASA systems were validated and used for various applications in dogs and to a lesser extent in cats. CASA systems offer an accurate, rapid, objective and simultaneous assessment of different semen parameters allowing the visual- ization of subtle changes in sperm characteristics, which cannot be identified by conventional semen analysis. The main problems of these computerized measuring devices are the relatively high investment costs and the need for standardiza- tion and validation before any practical use is possible. In comparison with automated motility and concentration assessment, automated morphometry and morphology assess- ment is more complex and time-consuming. Once validated, CASA systems can be routinely used in veterinary centres for assessment of fertility and for the improvement of sperm diluters, cooling and cryopreservation procedures in dogs and cats. Furthermore, information obtained by CASA systems could also be important when monitoring for example the effect of environmental stress on spermatozoa and for toxicity studies. In cats, CASA is less documented, and most studies describe the characteristics of epididymal sperm, which is frequently used for in vitro fertilization in cats. Implementa- tion of the CASA technique in cat reproduction could be interesting to further optimize assisted reproductive techniques in domestic cats and endangered wild felids. Introduction In the past, light microscopy was routinely used to evaluate the main sperm parameters, that is, concentra- tion, motility and morphology. The main problems when using these methods are subjectivity and variabil- ity mainly owing to the observer’s experience and the quality of the microscope. Additional drawbacks of these techniques are the low number of spermatozoa analysed, and the time needed to perform the evalua- tion. These drawbacks have led to the development of several computerized measuring devices. Computer-assisted sperm analysis (CASA) was orig- inally described by Dott and Foster (1979) more than 30 years ago in a wide variety of species including cattle, horse, pig, rabbit, rat and sheep and has gained increasingly more interest in veterinary medicine during the last decades. In dogs and cats, CASA was first described almost 20 years ago by Gu¨nzel-Apel et al. (1993) and Stachecki et al. (1993), respectively. Subse- quently, numerous commercial CASA systems including the CellSoft computer videomicrography, Stro¨ mberg- Mika Cell motion analyser, Hobson Sperm Tracker, Cell Track/s System, Hamilton-Thorne, Sperm Vision, Sperm Class Analyser were validated mainly in dogs and to a lesser extent in cats, both for research purposes and various clinical applications (Smith and England 2001; Verstegen et al. 2002; Rijsselaere et al. 2003; Scha¨fer- Somi and Aurich 2007; Dorado et al. 2011). The aim of this short review is to discuss the working mechanism, the main (dis)advantages and some possible applications of CASA systems in dogs and cats. Working Mechanism of CASA Computerized measuring devices generally consist of a phase-contrast microscope, a camera, a minitherm stage warmer, an image digitizer and a computer to save and analyse the data. These devices operate as a cell motion analyser, reconstructing sperm trajectories from the position of sperm heads in successive frames and calculating various motility and concentration parame- ters simultaneously. A playback facility inserted in most of these devices allows projection of the video sequences of the last field scanned, providing an additional control to validate whether all sperm cells were identified and whether their trajectory was reconstructed correctly. Evaluated Parameters and (Dis)advantages of CASA Motility and concentration parameters Computer-assisted sperm analysis systems offer an accurate, rapid and simultaneous assessment of different semen parameters such as concentration, total and progressive motility, slow, medium and rapid moving spermatozoa, linearity of sperm movement, the beat cross frequency, the amplitude of the lateral head displacement and different velocity parameters (Verste- gen et al. 2002; Rijsselaere et al. 2005). Therefore, these computerized measuring devices are valuable for the detection of subtle changes in sperm motion, which cannot be identified by conventional semen analysis. Moreover, high numbers of spermatozoa (several thousands) can be analysed individually within a short period of time (<1 min), which make these systems very practical for daily clinical use. Owing to the high concentration of fresh canine ejaculates, a predilution is usually required before the analysis by a CASA system can be performed. The main problems when using these computerized measuring devices are the relatively high investment costs and the need for standardization and validation of the system before any practical use is possible. The choice of internal image settings (e.g. minimum cell size, frame rate, analysis time), which is important to identify and reconstruct the trajectory of the different spermatozoa accurately, clearly influences the results obtained. Addi- tionally, significant alterations of CASA measurements © 2012 Blackwell Verlag GmbH Reprod Dom Anim 47 (Suppl. 6), 204–207 (2012); doi: 10.1111/rda.12057 ISSN 0936–6768