Simultaneous detection of viability and sex of bovine spermatozoa.

The viability and sex of bovine spermatozoa were simultaneously evaluated. After viability and acrosome staining with trypan blue/Giemsa, only live spermatozoa became decondensed by a modified papain-dithiothreitol method. Owing to this specific effect, live sperm heads were easily distinguished by their enlarged size and dark violet colour from small, light blue dead sperm heads. In the same sperm sample, X- and Y-chromosome-bearing sperm were distinguished by their fluorescent signal, using fluorescence in situ hybridization (FISH) with an XY paint set and 4,6-diamino-2-phenylindole counterstaining. The combined staining provides a method for morphological and viability evaluation before FISH and permits identification of the proportions of X- and Y-chromosome-containing live spermatozoa in a semen sample. However, only 25% of the undecondensed dead sperm express signals allowing detection of the sex of the chromosome. The method may be an effective tool in evaluating sex-oriented semen samples.