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United States Department of Agriculture

Agricultural Research Service

Ram Semen Protocol
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Ram Semen Processing and Cryopreservation Protocol


April, 2004


The concentration and motility of the semen sample are determined using spectrophotometry and a Hamilton Thorne motility analyzer (Beverly, MA), respectively (at least 7 fields of analysis and 1000 cells).  Semen samples are diluted to 200 x 106 cells per ml in egg yolk-Tris media (see recipe below).


The samples are then cooled to 5°C over 2 to 2.5 hours and loaded into 0.5ml straws.  The samples are frozen using the Cryo Bio System Mini Digitcool UJ400 (IMV Corporation, Minneapolis, MN) with the following curve: 5°C to -5°C at -4°C per minute, -5°C to -110°C at -25°C per minute, -110°C to -140°C at -35°C per minute, and plunged into liquid nitrogen for storage.


Cryopreserved samples are thawed for 30 seconds in a 37°C water bath and analyzed for motility as described previously.


Recipe: (Sanchez-Partida et al., 1998)

Egg yolk-Tris media

300mM Tris

28mM glucose

95mM citric acid

5% glycerol (by volume)

15% egg yolk

1mg/ml streptomycin sulfate

0.06mg/ml benzylpenicillin



Sanchez-Partida, L.G., Setchell, B.P., and Maxwell, W.M.C.  Effect of compatible solutes and diluent composition on the post-thaw motility of ram sperm.  Reprod. Fertil. Dev.  1975; 10, 347-357.

Last Modified: 5/2/2008