1. Frozen-thawed semen is also possible to use as research sample. But the spermatozoa pellet need to be washed by cold PBS supplemented with protease inhibitors at least three times to revise the proteins in the cryoprotectants.
2. The number of replication for 2D-PAGE, three biological replications and three technical replications. For mass-spectrometry, one repeat is the minimum but three biological repeats are preferred.
3. The sum of sample about 10 bulls of the same breed with fertility data is recommended to generate quality data that could be published.