SURVIVAL OF COW BLASTOCYSTS UTILIZING SHORT FREEZING CURVES

  • 1 January 1981
    • journal article
    • research article
    • Vol. 33  (12) , 523-529
Abstract
The survival of cattle blastocysts frozen 0.3.degree. C/min in 1.4 M glycerol/PBS [phosphate buffered saline] down to -15, -20, -25, -30, -35, -40 and -60.degree. C before being transferred into liquid nitrogen was investigated. In all trials thawing was done by direct transfer of the ampules into water at 37.degree. C. Pregnancy rates in the groups -20, -30 and -35.degree. C were 56, 57 and 59%, respectively. Survival rates were low in the -15 and -60.degree. C groups (11 and 13%) rising to 65% in the -20.degree. C group. The -25, -30 and -35.degree. C groups had a 75, 76 and 78% survival rate which dropped to 62% in the -40.degree. C group. Freezing and thawing rates in the -20 to -70.degree. C interval were 13.degree. C/s and 15.degree. C/s, respectively. Glycerol [1.4 M] was added to the PBS medium in 2 steps and removed in 4. All transfers were performed non-surgically within 2 h after removal of the cryoprotectant. In the present way of application glycerol is a better cryoprotectant than DMSO [dimethyl sulfoxide]. Cow blastocysts surviving plunge temperatures from -20.degree. C facilitates the use of long-term storage of cattle embryos by being less time consuming and also less demanding in expensive freezing equipment.