The test freeze is the first freeze performed on a stallion when he comes to a Select Breeders Services (SBS) Affiliate Lab to have semen frozen. We primarily have four different semen freezing protocols that we test on each stallion. The differences between each protocol being in either the extender formulation or the rate of cooling. For subsequent freezes we choose the protocol which gives the best results as determined by post-thaw motility. Regardless of the protocol, once the straws of semen reach -120 degrees Celsius in the programmable cell freezer they are then plunged into a bath of liquid nitrogen at -196 degrees Celsius.