Tissue sample for gDNA analysis are usualy stored in 100% EtOH, but i don't know if this aplies to sperm as well. The best thing would be to snap freeze it in liquid nitrogen.

Definitely snap freeze in liquid nitrogen.  It is critical that you do not go through multiple freeze thaw cycles so if you could aliquot it before you snap freeze it would be better. Do you plan to purify the DNA before you freeze or after?

Except you do want to extract and purify sperm DNA first, 100% EtoH may disintegrate viable sperm cells and may not make them fit for preservation. To preserve whole sperm to be analyzed later for its DNA content, there are vitrification kits you may consider using from Irvine Scientific. 

Dear Flueckiger and Kent-First,

Thank you for the responses. The best is to preserve the sperm in liquid nitrogen. May I know in brief what if meant by "purify the DNA before freezing"?

Dear Adenmosun,

I want to preserve the sperm for DNA to be analysed later. I will look for vitrification kit as suggested.

Instead of liquid nitrogen, is it possible to store the sperm in -80 oC without damaging the DNA?

storing probaply yes, but you would need te freeze the samples first in liquid nitrogen. The problem is, that if ou just put it to -80 °C the enzymes will still have plenty of time to damage your DNA or especially RNA

Dear Redzuan,

IN brief;

For BOVINE in particular, or almost all farm animals (including dog, etc);

I can only suggest you beforehand to start analysing the effect of ROUTINE (GIVEN/CHOSEN) handling (cryopreservation) steps either as single parameter or as a whole process (from semen collection to semen thawing and/or insemination). The ROUTINE Freezing means (According to ANDERSEN''s freezing method, dated around 1970's; 1969-1972): After preliminary steps before freezing (initial assessment, dilution, cooling, packaging, glycerolisation, equilibration, etc.), the straws will be frozen at 4 cm above the upper level of  liquid nitrogen (LN2) for 7 min, then plunging the samples into the LN2 for storage one 1 month or beyond. Thawing should ROUTINELY be preformed at 37 Degrees C for 30 sec. As all we know that these "FREEZE-THAWING" protocols allow VIABLE OFFSPRINGS since 50-fifty years. This BASICALLY means that DNA contents  as well as some part of controls (as both ESSENTIALLY needed for "successful" fertilisation afterwards) of sperm cells would either be preserved at least with a "MINIMUM tolerable cryodamage" level.

Afterwards, you may step forward with optimum protocol yet UNKNOWN (to my knowledge) or your BEST one (including COMPARISONS with SUPERIOR protocols each other).

Some DNA damage papers in dogs: Ström Holst et al., 1998; and in human: Royere et al., 1991. In this respect, I would further recommend you to study the effect of THAWING or POST-THAW Handling (considering the *osmotic changes* in particular) until the insemination occurs. We consider that the MAJOR part of CRYOINJURY occurs either during thawing and/or post-thaw handling (please see the papers of W.V. Holt, P. Watson, P. Mazur, and TJ Parkinson, etc).

Good luck & Regards,

Omer