An improved one-step straw method for the handling of frozen-thawed bovine embryos.

Abstract

An improved one-step straw method for bovine frozen-thawed embryos was described. The main objective was to remove the glycerol from the straw after thawing.After glycerol equilibration, the 0.25 ml straws were filled with four compartments, each separated by small air bubbles. In each straw two embryos were placed in the second upper compartment containing PBS and 10% glycerol as cryoprotectant. Other three compartments contained 0.3 mole sucrose solution (292 mOsm) supplemented with 20% bovine serum. After thawing at 37 to 38 C the straw was shaken once or twice, so that the embryos might migrate from the glycerol to the sucrose layer. Ten minutes after shaking, the glycerol layer moved to the upper part of the straw was re-moved by cutting about 1.5 cm from the tip. The straw containing the embryos was inserted into the plastic sheath for transfer and immediately transferred to 2 recipients (R-3 and 4). The other 2 recipients (R-1 and 2) were transferred the embryos taken out from the frozen-thawed straw.All the four recipients became pregnant.