Birth of Beagle dogs by somatic cell nuclear transfer.

The present study was undertaken to evaluate two enucleation methods for somatic cell nuclear transfer (SCNT), and to standardize the optimum number of embryos for transfer to each recipient for canines. Oocytes retrieved from outbreed dogs were reconstructed with adult somatic cells from a male Beagle dog. A total of 134 or 267 oocytes were enucleated either by aspiration or squeezing method, fused with two DC pulses of 1.75 kV/cm for 15 micros electrical stimulation, chemically activated after 1h of fusion using 10 microM calcium ionophore for 4 min and cultured 4h in 1.9 mM 6-dimethylaminopurine. Finally, 103 or 214 embryos for aspiration or squeezing method were transferred to 6 or 11 naturally synchronized recipients, respectively. A total of 53, 317 and 342 embryos were transferred to 7, 17 and 12 recipients for the group of 4-10, 11-25 and 26-40 embryos, respectively. There was no difference between fusion rate (76.87% vs. 80.15%), full term pregnancy rate (16.66% vs. 27.27%) and percent of live puppies born (0.97% vs. 1.87%) for aspiration and squeezing method (P>0.05). Production efficiency of cloned dogs was significantly affected by the number of embryos transferred to each recipient. No pregnancy was established for the group of 4-10 embryos (n=7) and 26-40 embryos (n=12) while pregnancy was detected in 23.53% recipients received a group of 11-25 embryos (n=17). Among them, five (1.76%) live puppies were born (P<0.05). These data show an increase in the overall efficiency of SCNT in canine species.