CRYOPRESERVATION OF OVINE EMBRYOS - SLOW FREEZING AND VITRIFICATION

Different methods for the cryopreservation of ovine embryos were evalu ated in vitro (survival upon culture in vitro) and in vivo (pregnancy and lambing rates after transfer in field conditions). In the first 2 experiments, slow freezing conditions were evaluated. When glycerol an d ethylene glycol were compared, no differences in the overall pregnan cy rate were found (40.2 vs 51.3%), but better results were obtained w ith ethylene glycol than with glycerol in morulae (29.7 vs 59.4%, P<0. 05). In the second experiment, 2 methods of removing ethylene glycol w ere compared: a 1-step procedure using 0.5-M sucrose and a 3-step proc ess for decreasing ethylene glycol concentration. There were no differ ences in the overall pregnancy rate (48.0 vs 48.0%) between the 2 meth ods. The last series of experiments were designed to compare 2 vitrifi cation solutions: propylene glycol - glycerol (PG) and ethylene glycol - Ficoll 70 - sucrose (EFS). There were no differences between the 2 vitrification solutions, based on the overall pregnancy rate (28.1 vs 40.0%). The vitrification technique and specially with EFS solution ha s resulted in good pregnancy rates. The EFS solution was particularly efficacious with morulae (55.5% pregnancy). These results demonstrate that vitrification with EFS can be used successfully for the cryoprese rvation of ovine embryos. (C) 1998 by Elsevier Science Inc.