Some percentage of sperm lost their viability during the freezing and thawing process. The rate of viability reduction depend on various factors such as, method employed, media used, personal expertize and quality of semen sample. If it is a good sample and if you employed correct procedures you can expect a good result. If the sample quality is low, it is advice to freeze more samples. 

I agree with Anura. We have (in human) no samples not usable for fertilization after freezing, at least using ICSI in men with not optimal sperm parameters.

you should expect that around 50% of spermatozoa will be damaged during freezing process even the sample is of good quality and the processing is efficient. So, you should start with the double concentration you finally need. Points described by Anura is important keep the sample around this figure.  

Good Luck 

As a bovine theriogenologist, my personal experience regarding sperm cryopreservation is that almost 50 % viability is lost in post thaw samples when compared with fresh one. However 40% motility with 10 % progressive motility is enough for fruitful conception. You can find the most relevant article in the link below.

http://thesciencepublishers.com/science_letters/v1i1abstract3.html

best of luck

The sperm sample once frozen and maintained in liquid nitrogen does not loose its viability over time.  Samples frozen more than 30 years ago have been used successfully. The damage however, happens during cryopreservation and thawing.  I highly recommend making a test unit along with the vials or straws meant for extended storage.  Post-thaw motility check of this test unit will provide assurance on how the sperm sample was frozen and about the quality of cryopreservation procedures.

I can understand that 50% of sperm losses viability but what about the 50% viable spermatozoa- the quality-structural and functional integrity, especially DNA damage ? 

If we can achieve fruitful conception without any teratogenic effect in the fetus, it means that there is no loss to the membrane functionality or DNA damage. More than 90 % of developed countries use AI for transfer of superior genetics. Even if there is some damage to the spermatozoa, it will never be able to achieve conception, in vivo. However there are some question marks about the Sexed semen as the extensive radiation can damage the DNA, but extensive studies are awaited. The semen extenders provide sufficient protection against cryoshocks. 

Dear Oladapo,

The aim of preservation of semen is to reduce metabolism of sperm cell in order to extend of life these cells. The best way to reduce metabolism of sperm cell is cooling or freezing. Theoretically, metabolism of freezing cells is "zero", because the water molecules can not moving so the cell is not aging or not affected by metabolites or reactive oxygen species. In this way you can preserve sperm cells during decades of years. However, ice formation during cryopreservation detrimentally affect cell membrane, acrosome membrane and mitochondral membrances and also DNA (in sperm cells DNA is more condensed and well packaged, so DNA fragmentation may be limited compared with somatic cells during freezing and thawing). Also an other affect called solution effect  forces membranes of  sperm cells during freezing and thawing process. As you know, some cryoprotectans are used  to reduce these detrimental effects, also cryoprotectants detrimentally affects sperm cells, but protects cells against detrimental effects of freezing.  Briefly, some sperm cells are damaged  during cryopreservation and thawing process, which causes reduction of viability and motility related with (cell or organelles) membrane damage. Theoretically, 50% viability and motility lost is expected during freezing and thawing processes, an other words you can preserve 50% motility and viability otherwise you will  lose all viability and motility of sperm cells. Sometimes, although you can well preserve motility of sperm cells, its thermo-resistance or fertile life of sperm cells will reduce following freezing and thawing process. Nevertheless, I mean 30, 40 or 50 % motility is better than 0% motility at the end of several years (storage period).

Mean while, I think there is a mistake,  the temperature of liquid nitrogen must be - 195,8 C (we practically say -196 C).  

My best wishes,

Umut