[en] The use of a simple cryopreservation method, adapted to direct transfer of thawed embryos may help to reduce the costs of embryo transfer in sheep and increase the use of this technique genetic improvement of this species. Two experiments were made to test a vitrification method that is easy to apply in field conditions. All embryos were collected at Day 7 of the estrous cycle of FSH-stimulated donor ewes and were assessed morphologically, washed in modified PBS and incubated for 5 min in 10% glycerol, for 5 min in 10% glycerol and 20% ethylene glycol and were transferred into the vitrification solution (25% glycerol and 25% ethylene glycol). All solutions were based on mPBS. Embryos were loaded in straws (1 cm central part, the remaining parts being filled with 0.8 M galactose in mPBS) and plunged into liquid N2 within 30 sec of contact with the vitrification solution. The straws were thawed (10 sec at 20 degrees C) and the embryos were either transferred directly or after 5 min of incubation in the content of the straw (followed by washing in PBS) into the uterus of a recipient ewe. In Trial 1, the pregnancy rates at term (72 vs. 72%) as well as the embryo survival rates (60 vs 50% respectively) were not different between fresh (n = 48 embryos) and vitrified (n = 50) embryos. In a second trial no difference was observed between vitrified embryos transferred after in vitro removal of the cryoprotectant (n = 86 embryos) or directly after thawing (n = 72) both in terms of lambing rate (67 vs. 75%, respectively) and embryo survival rate (lambs born/embryos transferred; 49 vs. 53%). This method of sheep embryo cryopreservation provided high pregnancy and embryo survival, even after direct transfer of the embryos.
Disciplines :
Veterinary medicine & animal health
Author, co-author :
Baril, G; INRA-PRC 37380 Nouzilly, France
Traldi, A L; INRA-PRC 37380 Nouzilly, France, France
Cognié, Y; INRA-PRC 37380 Nouzilly, France, France
Leboeuf, B; INRA-SEIA 86480 Rouillé, France, France
Beckers, Jean-François ; Université de Liège - ULiège > Département des sciences fonctionnelles (DSF) > Physiologie de la reproduction
Mermillod, P; INRA-PRC 37380 Nouzilly, France, France
Language :
English
Title :
Successful direct transfer of vitrified sheep embryos.
Acknowledgments The authors thank the Lacaune sheep-breeding associations (Conffidfration des Eleveurs de Roquefort and OVITEST) as well as F. Dupont and collaborators (INRA, Nouzilly) for care and treatment of donor and recipient ewes. The authors also thank Instruments de M6decine V6t6rinaire (IMV, L'Aigle, France) for designing the direct transfer device. Part of this work was supported by a grant from the "Bureau des Ressources G6n6tiques" (France). Dr A-L. Traldi was supported by an FAPESP (Brazil) post doctoral fellowship. ~' Present adress: Universidade de S~.o Paulo, Faculdade de Medicina Veterin~iria e Zootecnia, Departamento de Reproduq~.o Animal, c.p. 23, Pirassununga, SP, Brasil. b Correspondence and reprints requests.
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