Technological advances in breeding have allowed less sperm to be used per dose in artificial insemination, but evaluating sperm would allow further reduction with consistent results. Currently, sperm is evaluated for mobility and morphology using microscopes or Computer Automated Sperm Analysis (CASA), and sperm concentrations are taken by CASA or through photometric methods. Flow cytometry allows rapid analysis of concentration and characteristics, to sort X and Y populations for gender selection, and is becoming more accessible due to micro-fluidic capillary flow systems. Flow cytometry is used for bull semen, but is limited to adrology labs for boars at the moments. Although a definite fertility test is unlikely in the near future, flow cytometry allows multiple variants to be tested precisely, objectively, and in large samples. One assay that can be performed with flow cytometry is the Sperm Chromatic Structure Assay, which marks DNA with different coloured  fluorescent dye depending on whether it is normal or denatured. Another assay to determine sperm viability uses propidiom iodine to test the membrane integrity, which is more accurate than basing viability on mobility alone. Acrosome integrity can also be assessed at the same time as membrane integrity, and does so with specific dyes and plant lectin. There are also a variety of additional assays fluid cytometry is able to perform, which makes it a valuable and adaptable tool.