In vivo development of microinjected embryos from superovulated prepuberalslaughter lambs

This study was performed to investigate the developmental potential of micr oinjected embryos recovered from superovulated prepuberal lambs. Fifty-nine mixed-bred lambs (about 3 mo old) were superovulated either with 18 mg FSH -P with (Group FSH/+S) or without (Group FSH/-S) progestagen treatment, or with 10 mt Ovagen(R) following progestagen treatment (Group OVA/+S). Al ani mals received hCG to induce ovulation. Ovulation rates and the number of ov a recovered per animal for the different groups were 8.7 and 4.7 (55%, FSH/ +S); 7.3 and 3.2 (42%, FSH/-S); and 6.4 and 4.0 (65%, OVA/+S), respectively . No significant differences were seen in the ovulation and the recovery ra tes, but animals without progestagen treatment showed a significantly lower fertilization rate (44%) when compared with progestagen-treated groups (87 %; P<0.001). Foreign DNA was microinjected into the pronuclei of fertilized ova (n=155), which were transferred (n=98) into synchronized recipient ewe s (n=21). Two animals were detected pregnant and both gave birth to a singl e lamb. Results of superovulation and embryo recovery from prepuberal lambs were promising, but the low rate of development to term indicates that ova recovered from prepuberal lambs have reduced developmental competence in v ivo. Although 2 lambs were born, it seems that this is not a successful met hod for use in future gene transfer programs. (C) 1999 by Elsevier Science Inc.