Effect of the cryopreservation conditions on the viability of the rumen ciliate Diploplastron ( Metadinium ) affine

Aims:  To study the viability of Diploplastron ( Metadinium ) affine after its cryopreservation at two cooling rates, and the effect of procedure conditions on viability. Methods and Results:  There were differences in viability between cooling rates (1 and 4°C min −1 ) at 15 or 5°C, but not after thawing. When the equilibrium temperature (25 or 5°C), the cryopreservant (glycerol or dimethyl sulfoxide [DMSO]) and the use of membrane protector were tested, there were no differences caused by the cryopreservant or the membrane protector. However, the equilibrium at 25°C increased the viability ( P  = 0·005) compared with 5°C. Conclusions:  Viability after thawing was 0·10–0·19. Adding the cryopreservant (either glycerol or DMSO) at 25°C instead of 5°C improves viability of D. affine after thawing. Significance and Impact of the Study:  Conditions of cryopreservation are largely dependent on the species of rumen protozoa. Number of viable cells after thawing would indicate the possibility of culture recovery for D. affine .