RESUMO
The head area of bull spermatozoa was measured after viability and acrosome staining using trypan blue and Giemsa stains, followed by X- and Y-chromosome-specific fluorescence in situ hybridisation (FISH). The former staining made possible the categorisation of cells according to morphology and membrane integrity, whereas the latter allowed distinction of spermatozoa bearing X- and Y-chromosomes. Individual spermatozoa could be followed during the consecutive steps of staining, measurement and FISH. Using a high-resolution digital imaging system and measurement software, the head area of more than 3000 cells of five bulls was determined precisely. In all bulls, morphologically normal, viable cells with intact acrosomes were significantly smaller than dead cells with damaged acrosomes. No significant difference in the head area between X- and Y-chromosome-bearing viable, acrosome-intact spermatozoa was found in individual bulls. However, significant between-bull differences were detected in all cell categories.