• Journal of Embryo Transfer
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• v.22 no.2
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• pp.89-95
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• 2007

The present study was conducted to examine some factors affecting in vitro development and fecundity of embryos recloned with somatic cell nuclear transfer (SCNT). Fibroblast cells retrieved from the ear of a 3-week-old, cloned Korean goat (Jinsoonny) were used as karyoplast donors and serum-starvation was conducted in tissue culture medium (TCM)-199 supplemented with 0.5% FBS. Recipient oocytes were surgically collected by flushing the oviducts 35 h after hCG injection following FSH priming. The zonae pellucidae of the oocytes were partially perforated with a laser drill and a donor cell was transferred into an enucleated oocyte. The couplets were electrically fused and activated by ionomycin (5 min) and 6-DMAP (4 h). The reconstructed embryos were cultured in mSOF medium containing 0.8% BSA at $39^{\circ}C$ in an atmosphere of 5% $CO_2$, 5% $%O_2$, 90% $N_2$ for 12 to 15 h. Re-cloned embryos (2- to 4-cell stages) were surgically transferred into the oviducts of the recipients and pregnancy was subsequently diagnosed by progesterone assay and ultrasound on Days 21 and 63 of pregnancy. The fusion rate following 1st fusion pulse was higher (p<0.05) in 2nd cloning (65.9%) compared to 1st cloning (51.0%), but it was not different in the other groups. The rate of cleavage after fusion was significantly higher (p<0.05) in 1st (77.7%) than in 2nd cloning (56.0%). A total of 175 re-cloned embryos were transferred into 28 recipients. On day 21 and 60 after transfer, 11 (39.3%) and 4 recipients (17.4%) were pregnancy, respectively. In comparison of pregnancy rate by estrous synchronization, a total of 66 and 109 re-cloned embryos were transferred into 11 recipients in natural estrus and 17 recipients in induced estrus, respectively. Five (45.4%) and 2 recipients (18.2%) in natural estrus were pregnant on days 21 and 63 while 6 (35.3%) and 2 (11.8%) recipients in induced estrus were pregnant, respectively. These results show that recloning of goat can be achieved by SCNT and estrous synchronization between donor and recipient animals may be one of the major factors affecting success rate.